Rinsing with Green Tea Improves Oral Health

Rinse with green tea and keep your teeth happy. (Photo by Daria)

I've written before about the protective effects of green tea against dental caries. Several studies have shown that green tea helps tooth and gum health by reducing harmful bacteria, increasing enamel strength and inhibiting the breakdown of starch to sugar.

Black tea, cocoa and coffee protect against oral problems too, but green tea seems to be the most effective. A new study sheds more light on how drinking green tea improve oral defense mechanisms through oral peroxidases (OPOs) (link).

The two major defensive peroxidases of the mouth are salivary peroxidase (SPO) and myeloperoxidase (MPO). Their function depends partly on diet and probably also on genes.
In the abstract of the paper, the authors mention that their earlier study showed that elderly people who drank green tea for 3 months had higher levels of oral peroxidase activity than non-drinkers. In this study, they compared the effects of green tea on OPO in vivo and in vitro.

Adding a green tea infusion to saliva increased oral peroxidase activity by 280%, while black tea increased it by only 54%. Adding only epigallocatechin gallate (EGCG), the main polyphenol in green tea, increased activity by 42%. The effect was dose-dependent, which I assume here means that the stronger the tea, the greater the effect.

In human subjects, green tea gave a very similar result. Mouth rinsing with a green tea infusion resulted in a 268% increase in OPO activity. Thus, while green tea extracts may be more useful than just drinking regular green tea for some purposes, for dental health drinking and/or rinsing is probably the most effective way.

Note, however, that higher levels of salivary peroxidase don't necessarily mean better oral health; in fact, people with more dental caries and gingivitis tend to have higher SPO activity (link). My guess is that this is a defense mechanism against the harmful effects of excess hydrogen peroxide, which is excreted by oral bacteria. In other words, the stronger the attack, the stronger the defense.

In the case of green tea it seems that increasing SPO really does lead to better oral health, though.

For more information on green tea and dental health, see these posts:

Drinking 10 Cups of Green Tea Daily and Not Smoking Could Add 12 Years to Your Life
Green Tea Extract Enhances Abdominal Fat Loss from Exercise
Vegetable vs. Animal Sources of Vitamin A: Why Eating Carrots Isn't Enough
Genes, Diet and Oral Health: Why Do Some People Get Cavities and Others Don't?

Antioxidants and Intermittent Fasting – Good For Longevity?

Are blueberry antioxidants beneficial for intermittent fasting? (Photo by Simply Bike)

Is it possible to live longer by combining the benefits of intermittent fasting (IF) and plant polyphenols? A new paper claims that taking polyphenol antioxidants during dietary restriction increases the lifespan of mice more than dietary restriction alone. The antioxidants used in the study were blueberry, pomegranate and green tea extracts.

The subject of the paper – "Potentiation of dietary restriction-induced lifespan extension by polyphenols" – is certainly enough grab the attention of anyone interested in life extension. The abstract seems promising too (link). Here's a quote:

Dietary restriction (DR) extends lifespan across multiple species including mouse. Antioxidant plant extracts rich in polyphenols have also been shown to increase lifespan. We hypothesized that polyphenols might potentiate DR-induced lifespan extension. [––] Polyphenol compounds may potentiate IF-induced longevity by minimizing specific components of IF-induced cell stress.

Let's look at these claims in more detail. First off, it's not clear from the abstract what exactly the authors mean by "dietary restriction". The full paper, however, reveals that they use the term to describe pretty much any kind of diet where access to food is limited, including traditional calorie restriction and intermittent fasting.

The longevity confusion

The problem with that opening sentence is that dietary restriction extends lifespan across multiple species only when it equals calorie restriction. That is, you can make a mouse live longer by only feeding every other day, as long as it results in less calories consumed. This is an important distinction, because many people – including longevity scientists – keep propagating the myth that intermittent fasting has the same benefits as calorie restriction. It doesn't. The reason that IF prolongs lifespan in some species is because the animals fail to compensate for the missed calories on their feeding days.

The next sentence is just as problematic. Yes, plant antioxidants have been shown to increase lifespan, but the question is, compared to what? So far, no one has succeeded in exceeding the known maximum lifespan of mice by feeding them antioxidants. Instead, what we see in many studies is that the antioxidant group lives longer than the control group.

The problem is that almost always, neither group lives very long. Poor diets, poor animal husbandry, poor environment – all play a role in how long the animals live. So, in essence, the antioxidants merely make the unhealthy mice a bit healthier. But this is like making a human live 70 years instead of 60 years by giving them some veggies with his daily bread and then claiming that "vegetables extend human lifespan".

Comparing lifespans

That said, there are some interesting figures in the full paper. The graph below shows the survival rates of the three groups; one fed the control diet, the second fed the same diet but only every other day, and the third fed a diet supplemented with polyphenols every other day:

There's a big drop in the survival rate of the control group around 22 months. For the IF groups, the survival curves look a lot better. So how does this compare to the average lifespan of similar mice kept in good laboratory conditions? Here's a graph of age ranges and survivorship of C57BL7/6J mice (the same strain used in this study):

This survival curve is based on a cohort of 150 male and 150 female mice. As you can see, at 28 months half of the mice are still alive. That's about 850 days, which is a pretty normal figure for mean lifespan of this strain of mice in the literature.

Once again, in the antioxidant study the control group dies earlier than is normal. For some reason, half of the mice are dead at 22 months instead of 28 months. One possible reason is the use of a high-fat diet to "mimic the effects of a Western diet", as the authors put it. This seems like a strange idea to me, because a typical Western diet is no more a high-fat diet than it is a high-carbohydrate diet. Furthermore, plenty of humans (myself included) seem to do quite well on a high-fat diet, whereas with mice it's somewhat different.

The survival curve of the IF mice in the first graph is slightly better than that of the normal-fed mice in the second graph. But that is hardly a surprise, given that both the IF group and the IF + antioxidant group had lower body weights than the control group. In other words, the intermittent fasting once again made the mice eat less than the control group, which in turn resulted in a slightly longer lifespan. It's good to keep in mind, however, that with just 10% calorie restriction longer lifespans have been reported in other studies, so the result is not too impressive.

Conclusion

Perhaps the most interesting result is that the IF + antioxidant group lived slightly longer than the IF group. There's no concensus as to whether it's a good idea to combine CR or IF with antioxidants. It may be that plant polyphenols are essential for optimal nutrition and good for activating sirtuins (which play at least some role in longevity), but there is also some evidence suggests that taking antioxidants may interfere with hormesis and thus diminish the effects of CR.

In this study, the antioxidants had a beneficial effect. While the IF diet by itself activated pro-inflammatory pathways, adding plant polyphenols to the diet blocked this effect. The authors identified 20 gene sets that were down-regulated by the addition of polyphenols, most of them related to immune response, inflammation, cell differentation and tumorigenesis. 

This suggests that if you're doing intermittent fasting, adding some blueberries, pomegranates and green tea to your diet may not be such a bad idea. Note, however, than the mice did not have access to polyphenols during their fasting days, so this study tells us nothing about taking antioxidants during fasting. It also doesn't say much about how polyphenols affect regular calorie restriction without IF in humans.

For more information on intermittent fasting and longevity, see these posts:

Lithium in Drinking Water May Lead to Longer Life
Does Intermittent Fasting Increase Lifespan?
Alternate-Day Feeding and Weight Loss: Is It the Calories Or the Fasting?
Slowing Down Aging with Intermittent Protein Restriction

Green Tea as a Pro-oxidant: Too Much of a Good Thing?

Is too much green tea harmful for you? (Photo by tornado_twister)

I was browsing through the latest studies on green tea and came across a paper saying EGCG, one of the green tea polyphenols, increases protein cross-linking (link). I was intrigued, because this was the first time I'd heard of such an effect. The abstract also mentions that there's increasing evidence EGCG can generate reactive oxygen species and break DNA strands in biological systems. In effect, it says that the antioxidant is actually a pro-oxidant.

I looked up some of the references and indeed, even green tea's polyphenols (at least EGCG, possibly some others) have oxidative effects under certain in vitro conditions. For example, in human whole blood lymphocytes, EGCG either suppresses or induces DNA strand breakage, depending on the concentration.

In concentrations between 0.01-10 μM (micromoles/L), strand breakage decreases, but once the concetration gets higher than 1000 μM, it increases instead. In purified blood lymphocytes, concentrations of 1-100 μM induce and concentrations of 0.01-0.1 μM suppress DNA strand breakage.

Sounds an awfully lot like hormesis, doesn't it? As with everything, the dose makes the poison. The interesting part, of course, is whether drinking green tea can cause similar harmful effects in real life.

Luckily, one study looked at the effect of green tea on DNA strand breaks in rats (link). The smaller dose (which according to the authors is equivalent to one desiliter of green tea in humans) had no effect, but the larger dose (equivalent to half a liter) significantly reduced strand breaks.

Half a liter of green tea, equal to about three cups, increase total plasma antioxidant capacity only moderately. When only EGCG is taken into account, the results vary somewhat from study to study, but concentrations rarely exceed 1 μM (link). Also, plasma antioxidant activity has a plateau, which suggests that the absorption mechanism of green tea polyphenols becomes saturated after a certain point:

To make the tea used in the study, 500 ml of boiling water was poured on 20 grams of green tea leaves (8-10 tea bags), and the tea was then allowed to infuse for 10 minutes. That makes for a very strong tea, much stronger than the ones used in the other studies. The volunteers drank 300-400 ml of the tea, after which blood samples were collected at different time intervals

In this study, there was no difference between those who drank 300 and 400 ml of the tea. Even then, the increase in antioxidant activity was only 4% at the peak. Thus, it seems unlikely that harmful levels could be reached by simply drinking plenty of green tea. In one Asian population, 10 cups of green tea daily reduced total mortality compared to those who drank less green tea and/or smoked.

Theoretically at least, extracts and supplements could be a different matter, because they often contain a higher percentage of EGCG than green tea and come with things that increase absorption. For example, piperine increases plasma levels of EGCG.

One green tea extract containing 40% EGCG resulted in a peak  of 0.8 μg/mL in human subjects; when the same extract was complexed with phospholipids, the peak was 1.9 μg/mL. If my calculations are correct (which they often aren't; please correct me if I'm wrong), then these would be ~1.75 μM and ~4.14 μM, respectively. Again, in whole blood lymphocytes concentrations between 0.01-10 μM, strand breakage was decreased, and it took concentrations higher than 1000 μM to increase strand breakage.

All in all, it appears that green tea in reasonable quantities (at least up to 10 cups) does not cause it to act as an oxidant in vivo. It's unknown what a much higher amount would do, assuming you could somehow bring yourself to drink 50 cups. I haven't seen any human studies on such amounts. But if the plateau effect is indeed true, then you might not be able to reach high plasma levels of EGCG no matter how much you drink.

With supplements, the situation is different. Piperine and phospholipids make reaching higher plasma values possible, which can be a good thing or a bad thing, depending on what you're using the supplements for. Some conditions require higher doses than others, so you'll have to judge the proper approach on a case by case basis. However, since EGCG does have the potential of being a pro-oxidant in vitro and is toxic to the liver in very high amounts, be careful not to overdo it with green tea supplements.

For more information on green tea and health, see these posts:

Green Tea Protects from the Psychological Effects of Stress in Rats
Tea, Coffee and Cocoa: All Good for Your Teeth
Green Tea and Capsaicin Reduce Hunger and Calorie Intake
Green Tea Catechin Reverses the Effect of DHT in Prostate Cancer Cells

Hibiscus Tea Increases HDL, Lowers LDL and Triglycerides

 

Hibiscus tea is often served cold with sugar. (Photo by molossoidea)

When it comes to health benefits and drinks, green tea gets most of the publicity. And with good reason – from what we know, it seems to have the widest range of positive effects out of all beverages. But that's not to say that there aren't other less known drinks out there that have health benefits of their own.

One such beverage is hibiscus tea, a herbal infusion made from the calyces of the Hibiscus sabdariffa flower. Hibiscus is also known as sorrel, roselle, karkadé and flor de Jamaica, depending on the region. Earlier this year, I wrote about two studies showing that hibiscus tea reduces blood pressure. In the second study, hibiscus tea was compared with black tea, and guess what – hibiscus tea wone hands down.

In fact, the group that drank black tea saw an increase in blood pressure. That was black tea – as far as I know, there have been no direct comparisons between green tea and hibiscus tea, but even green tea's effects on blood pressure seem to be small or nonexistent. So green and black tea, while very healthy, may not be enough if you want to cover all bases.

I wrote in the earlier posts that to my knowledge, there had been no studies on hibiscus tea and cholesterol, even though the drink is traditionally used to lower cholesterol. Today, however, I found a paper that shows hibiscus tea is good for cholesterol too (link). Granted, the paper appeared in the Journal of alternative and complementary medicine, which has published some papers that seem to be of questionable quality, but this one seems pretty legit.

For the experiment, 60 patients with type II diabetes were randomly assigned into two groups. One group got black tea and the other got hibiscus tea (which the authors refer to as "sour tea"). The participants were told to drink one glass (1 tea bag in boiling water, steeped for 20-30 minutes) twice a day for a month.

The subjects that drank black tea did not show improvement in any of the parameters measured. None of the changes in total cholesterol, LDL, HDL, triglycerides and lipoprotein (a) were statistically signifcant.

Those who drank hibiscus tea, on the other hand, saw several improvements in their cholesterol levels. Total cholesterol went from 236.2 to 218.6 mg/dL. HDL increased from 48.2 to 56.1 mg/dL, while LDL decreased from 137.5 to 128 mg/dL. Triglycerides went down rather dramatically, from 246.1 to 209.2 mg/dL. Lipoprotein (a) was unchanged.

The authors also reference several other papers showing similar results in humans and animals. For example, one study showed a reduction in cholesterol levels in healthy men and women taking a hibiscus extract (link). This would suggest that the beneficial effects of hibiscus are not only limited to diabetic patients.

I'm not sure why I didn't find these papers the last time I did a pubmed search, but I'm glad I came across them now. I guess it's time to put hibiscus tea back on the menu, next to green tea and rooibos tea.

My favourite way to drink it is to make a big glass of hibiscus tea the normal way, then after 15 minutes of steeping pour the tea through a sieve into a larger container, add twice as much cold water and put it in the fridge. It's ready to drink in about an hour. It's especially good in the summer, best enjoyed with ice and a little sugar for taste.

For more information on tea, cholesterol and health, see these posts:

The Many Health Benefits of Rooibos Tea
Black Tea Is More Effective in Activating Superoxide Dismutase (SOD) than Green Tea
Refined vs Red Palm Oil and Cholesterol
Anthocyanins from Berries Increase HDL and Lower LDL

Ashwagandha as a Nootropic – Experiment Update

The search for nootropic herbs continues. (Photo by Jim Brekke)

It's time for an update on my self-experiment with Ashwagandha, which began earlier this year in February. The herb in question, also known as Withania somnifera, is one of the many used in Ayurvedic medicine. Since many people use it as a nootropic, being a fan of cognitive boosting I figured I had to try it myself.

While Ashwagandha is commonly used for its relaxing properties, a review of the literature shows that it has a range of benefits. I've gone through the nootropic effects of Ashwagandha in detail in my previous post, so I'll only list them briefly here:

• Activates the GABA receptor
• Inhibits acetylcholinesterase (AChE)
• Reduces alcohol and morphine addiction
• Decreases stress
• Improves sperm count and motility
• Increases testosterone and reduces prolactin levels
• Improves memory function in mice
• Regenerates nerve fibers and dendrites
• Little or no risk of toxicity
• Negative effects on libido at very high doses

An impressive list, as you can see – but note that some of the results are from rodent studies or studies on humans suffering from high stress. The fact that Ashwagandha has been shown to bring things back to normal, so to speak, doesn't necessarily mean that it'll improve things beyond baseline in healthy people. Indeed, Ashwagandha is considered an adaptogen, which refers to herbs that supposedly normalize the body's functions.

For the purposes of my experiment, I bought a bottle of NOW Foods' Ashwagandha extract, which contains 450 mg of the root extract (standardized to a minimum of 4.5 mg withanolides) per capsule. My evaluation was based on subjective effects on mood, libido and stress.

The bottle is now finished, and I'm somewhat disappointed to conclude that I didn't notice much effects from the product. I tried various approaches: taking a capsule in the morning, during the day, or in the evening, but none of them resulted in anything clearly noticeable. The only possible effect I saw was more vivid dreams when I took Ashwagandha before going to sleep, but even then the results were inconsistent. All I can say is that the combination of magnesium and Ashwagandha before bed seemed to give me a good night's sleep.

As for boosts in mood or cognition, I didn't see any. Neither did I notice a difference in my libido or stress levels. I did try taking two or three capsules at once to see if a larger dose would help, but as far as I can tell, it made no difference. At least there were no negative effects either.

To be clear, I'm not saying that Ashwagandha is useless, just that this particular product at these doses didn't do anything for me. NOW Foods has very reasonably priced products, but there are probably several ways of making a herbal extract and a wide range of effectiveness between brands, so I'm tempted to try a couple of different brands before concluding the experiment.

The active ingredients in Ashwagandha are supposedly the withanolides, so in theory, any product that contains a sufficient amount of them should give similar results. Nonetheless, based on other people's experiences, some brands may be more effective than others. If you have personal experiences (positive or negative) with Ashwagandha, please share them in the comment section. Specifically, if you can recommend a brand that worked for you – preferably one that is available at iHerb – I will consider trying that product next.

For more information on nootropics and cognition, see these posts:

60 Minutes on Boosting Brain Power
Nootropic Battle Conclusion: Acetyl-L-Carnitine vs. Ginkgo Biloba vs. Taurine
Green Tea Protects from the Psychological Effects of Stress in Rats
Does Ginkgo Biloba Improve Cognitive Performance?

What a "Heart-Healthy" Diet Does to Your Cholesterol Levels

It's the butter that is bad for you, not the bread... right? (Photo from flickr.com)

What happens when you follow the American Heart Association's dietary recommendations? You know, a diet high in whole grain, vegetables, fruit and berries, but low in animal protein and fat, especially that nasty artery-clogging saturated fat.

According to conventional wisdom, you will be healthier in general. In particular, your cholesterol levels are supposed to improve – though it's never quite clear what "improvement" here means. Is it lower total cholesterol? Or perhaps lower LDL and higher HDL? And what about triglycerides and oxidized LDL?

Fortunately, a few years ago the Journal of the American Heart Association published a study that looked at what happens to cholesterol levels while on the officially heart-healthy diet (link). In contrast to many other studies, the participants in this one were healthy and had normal cholesterol levels to begin with. The idea was to see whether adopting an optimal diet would make them even healthier.

Study design and composition of diets

The study included 37 healthy women and consisted of two phases. During the first phase, the women followed a low-fat, low-vegetable diet for five weeks. After that, there was a three week washout period, followed by the second experimental diet. This second diet was the "optimal" diet, which was also low-fat but this time included lots of vegetables, fruit and berries. To make sure that the dietary guidelines were followed, the meals were supervised.

Both diets included 8 portions of grain products, 3-4 portions of low-fat or fat-free dairy products, and 2 portions of lean meat, chicken or fish. In the first phase, the subjects were given 2 portions of fruit and vegetables per day. In the second phase, the amount of fruit and vegetables was increased to 4-5 and 5-6 portions, respectively.

Dietary fats were replaced vegetable oils and spreads which contained minimal amounts of trans fats. The amount of total fat and saturated fat decreased, whereas the amount of polyunsaturated fats increased. To replace the lost calories, the subjects ate more carbohydrates and protein. Fiber intake also increased; in the second phase, it was nearly twice as much as at baseline.

Thus, both diets were very close to official recommendations: they included only moderate amounts of fat and animal protein, the fat was mostly from vegetable oils high in polyunsaturated fatty acids, dairy products were low in fat or fat-free, and grain products high in fiber were included. In addition, the second phase was high in veggies, fruits and berries.

HDL, LDL and triglycerides

After the low-fat, low-vegetable phase, total cholesterol was unchanged. On the other hand, triglycerides and HDL decreased, while LDL levels increased. The increase in LDL was apparently not statistically significant, which is probably due to the small sample size.

When the amount of vegetables, fruit and berries was increased, total cholesterol decreased. Triglycerides remained the same, but both HDL and LDL decreased:

Thus, reducing the amount of fat in the diet and replacing animal fats with vegetable oils did not change total cholesterol but did change the cholesterol profile: HDL and triglycerides decreased, while LDL increased. From the "good cholesterol, bad cholesterol" standpoint, adopting a low-fat diet actually changed things for the worse.

Things were not much better when vegetables, fruit and berries were added to the low-fat diet. Total cholesterol was clearly reduced, which by some standards is admittedly a positive change. Importantly, however, this change was not achieved through a decrease in "harmful" LDL but in "healthy" HDL.

The amount of triglycerides did decrease compared to baseline, but the reason is unclear. Generally, replacing fats with carbohydrates seems to increase triglycerides. Also, triglycerides decreased after the first phase, when the diet was low in vegetables, and did not decrease further after the second phase, so dietary antioxidants don't seem to be the explanation either. One thing that comes to mind is alcohol intake, which is not reported in the study. Perhaps the subjects reduced their alcohol intake while on the experimental diets? That would show up as a lower triglyceride score, but we can't know for sure.

Oxidized LDL and lipoprotein (a)

Both oxidized LDL and lipoprotein (a) are independently associated with a higher risk of atherosclerosis – more so than total cholesterol or LDL. In fact, oxidized LDL (ox-LDL) is believed to cause clogging of arteries and inflammation. Lipoprotein (a), also called Lp(a), is a known risk factor in many cardiovascular diseases, although its function is not entirely understood.

The most interesting result of the study is that the number of oxidized LDL particles and Lp(a) increased significantly as a result of following the low-fat diets. Oxidized LDL increased by a whopping 27% in the first phase. Even after vegetables, fruits and berries were added to the diet, ox-LDL levels were still 19% higher than at baseline. Similarly, Lipoprotein (a) was 7% higher after the first phase and 9% higher after the second phase compared to baseline.

What this means is that two important risk factors of atherosclerosis worsened markedly after following the very dietary recommendations that are supposed to reduce risk of atherosclerosis. Although plasma antioxidant capacity correlated with the intake of fruit, vegetables and berries, the antioxidants in them were clearly not enough to protect from these harmful changes.

The changes in total cholesterol, HDL, LDL and triglycerides were relatively small, which may be partly due to the short duration of the study. However, the 27% increase in ox-LDL demonstrates that diet can have a dramatic even in a short period of time.

Conclusion

The authors describe the results as "unexpected". According to them, a decreased intake of fat – especially saturated fat – should have led to a decrease in risk factors. They quote a number of studies where replacing saturated fatty acids with polyunsaturated fatty acids led to a "beneficial" decrease in total cholesterol. So why did the risk factors of atherosclerosis not see a similar "beneficial" change?

It is true that fats and oils high in polyunsaturated fatty acids generally tend to lower cholesterol (although the relationship between different fatty acids and cholesterol is more complicated than that). A completely different question is whether total cholesterol even matters, however. Even official recommendations acknowledge that the ratio of LDL to HDL is a better predictor of CVD than total cholesterol.

As was to be expected, the low-fat diets in this study did reduce total cholesterol. But if that decrease happens by reducing HDL and not changing or even increasing LDL, is the change really for the better? Most importantly, if the drop in total cholesterol comes with a marked increase in Lp(a) and oxidized LDL, can the results really be seen as beneficial?

Since the results of the study are incompatible with the cholesterol hypothesis and dietary recommendations, the authors came up with an alternative explanation. According to their hypothesis, high Lp(a) and ox-LDL may in fact be a sign of existing artherial damage being fixed and therefore a positive thing – but of course only in the case of low-fat diets. Right.

For anybody who has been keeping up with the gradual destruction of the cholesterol hypothesis, these results are not all that surprising. For example, we already know that polyunsaturated fatty acids oxidize much more easily than monounsaturated or saturated fats. It seems logical that LDL would be oxidized also.

What is somewhat surprising, however, is that the study was published in a journal that promotes the official dietary recommendations as heart-healthy.

For more information on cholesterol and diets, see these posts:

Which Oils and Fats Are Best for Cooking?
Carotenoids and Lipid Peroxidation: Can Vegetables & Fruit Reduce ALEs?
Sugar and AGEs: Fructose Is 10 Times Worse than Glucose
Anthocyanins from Berries Increase HDL and Lower LDL

Black Tea vs Green Tea: AGEs and ALEs

Theaflavins are black tea's answer to catechins in green tea. (Photo by Caro Wallis)

In previous posts, I've mentioned studies that have shown contradictory results for the effectiveness of green tea against advanced glycation end-products, or AGEs. At the time when the first post was written, I found five studies showing that green tea reduces AGE formation.

In a later post, I wrote that another in vitro study found yerba mate to inhibit AGE formation as effectively as aminoguanidine, which is one of the strongest anti-glycation drugs around. The bad news was that the same study found only a non-significant effect on AGEs from green tea. So what gives?

One possible reason for this discrepancy is dosage; perhaps low doses of green tea catechins are ineffective against glycation. Indeed, the yerba mate study used concentrations that were easily achievable in humans, whereas some of the others used stronger extracts. While a few cups of green tea may not do much in terms of AGEs, it's nonetheless promising that three of the five positive studies were in vivo. One of them was in diabetic rats and two of them were on normal rodents.

The problem with drinking copious amounts of yerba mate is that several reviews have found it to be carcinogenic. I will probably do another post on this, but based on my current knowledge, it looks like less than half a liter per day is not associated with an increased risk of esophageal cancer, while at higher levels the risk becomes clear. That means drinking enough yerba mate to inhibit AGEs may not be a smart choice.

If drinking 10 cups of green tea per day seems like a daunting task, rooibos tea is one alternative. We know that rooibos tea reduces lipid peroxidation, which causes advanced lipid peroxidation end-products, or ALEs. But there are no studies suggesting it reduces AGEs, so we're left looking for more alternatives to green tea.

Enter black tea. Most people consider green tea to be superior to black tea in all aspects, but that's not entirely true. Granted, green tea does often beat black tea because the latter contains fewer catechins, but there are also cases where black tea prevails. This is because during the longer fermentation process (which separates green tea from black tea), some of the catechins are converted to theaflavins – polyphenols unique to black tea.

AGEs in vitro: comparing black tea and green tea

Methylglyoxal (MGO) and glyoxal (GO) are highly reactive dicarbonyl compounds that modify proteins over time, forming AGEs. Although it's still unclear how harmful they are in healthy people, AGEs are known to be higher in chronic diseases such as diabetes, and levels of MGO are also 2-6 times higher in diabetics than in normal people.

In one study, epigallocatechin gallate (EGCG) – the main catechin in green tea – was found to trap both GO and especially MGO under neutral or alkaline conditions (link). Under acidic conditions (pH less than 4) this effect was not present. EGCG was as effective as aminoguanidine, which also works by trapping reactive dicarbonyl compounds.

The authors then decided to test whether other tea polyphenols might have a similar effect. And indeed they did. All of the catechins tested reduced MGO, with epigallocatechin (EGC) being the best of the four. However, they also found that black tea theaflavins outperformed all green tea catechins in reducing MGO. All theaflavins tested decreased MGO by more than 60%.

The concentration of catechin or theaflavin was the same in each test, which means that theaflavins clearly have the upper hand here. GA and PY in the above graph stand for gallic acid and pyrogallol, respectively. Interestingly, when the molar ratio of polyphenols to MGO was increased from 1:3 to 1:1 in a second experiment, some of the catechins did slightly better than theaflavins.

The difference between in vitro and in vivo

So black tea looks effective in vitro, but what about in vivo? Some studies suggest that even a few cups of green tea or black tea increases antioxidant activity in plasma, but it's not clear whether this translates directly to less AGEs and ALEs. The data on black tea and AGEs in vivo is very limited, so we'll have to focus on ALEs instead.

Green tea or black tea powder seems to protect rat livers from lipid peroxidation (link). Green tea also inhibits lipid peroxidation in their central nervous tissue – which is high in easily oxidizable polyunsaturated fatty acids. Levels of malondialdehyde (MDA), an intermediate in the formation of ALEs, were significantly reduced.

Similar findings were reported in another study, in which rats fed black tea instead of water had lower plasma MDA and protein carbonyl contents (link). Thus, black tea was effective against both ALEs and AGEs.

One study found that while black tea polyphenols strongly reduced plasma lipid peroxidation in vitro, but when human subjects were given a drink containing black tea extract, the rate of lipid peroxidation did not change (link). According to the authors, the concentrations of polyphenols in plasma would have to have been at least five times greater (5 micromoles) to see a significant effect.

Another study found that tea flavonoids reduced LDL oxidation in vitro (oxidised LDL seems to be a key player in atherosclerosis), with theaflavins being more effective than catechins (link). Then, human volunteers were given 750 mL of black tea for 4 weeks to see if the same thing happened in vivo. Although the concentration of polyphenols was now much lower, tea consumption still had a significant inhibitory effect on LDL oxidation.

Unfortunately, other studies have failed to validate this finding. Human volunteers given 900 mL (6 cups) of green tea or black tea daily for 4 weeks did not have lower levels of LDL oxidation or lipid peroxidation, even though green tea slightly increased plasma antioxidant activity (link). Since both were effective in vitro, the authors conclude that the amount of polyphenol needed is far greater than what could be achieved by drinking tea.

Another similar study found that 6 cups of green tea or black tea daily did not reduce LDL oxidation in smokers, even though they were found to be effective in vitro (link). Increasing the dose by drinking more tea does not seem feasible. Even a green tea extract equivalent to 18 cups of green tea was ineffective in the same study, and another study found that 1,000-1,250 mL of tea did not reduce markers of lipid peroxidation (link).

In one study, smokers and non-smokers were put on a diet otherwise low in flavonoids and given green tea extract with their food (link). The daily intake of catechins was 18.6 mg. No changes in markers of AGEs or ALEs was seen, although the green tea extract increased plasma antioxidant capacity, especially in smokers.

Conclusion

Black tea polyphenols are effective in inhibiting AGE and ALE formation in vitro, in some cases even more effective than green tea catechins. Green tea and black tea seem to be effective also in vivo in rodents, whereas human data is mostly disappointing.

A probable reason for the mismatch between in vitro and in vivo results is that the bioavailability of tea polyphenols is very low. Even large consumption of tea did not reduce lipid peroxidation in most human studies. Unfortunately, there are no studies looking AGEs and tea polyphenols in humans.

A closer look at the absorption of tea polyphenols and whether their bioavailability can be improved is probably in order, but we'll save that for another post. For more information on tea, AGEs and ALEs, see these posts:

Hibiscus Tea Lowers Blood Pressure
Green Tea Protects from the Psychological Effects of Stress in Rats
Carotenoids and Lipid Peroxidation: Can Vegetables & Fruit Reduce ALEs?
Fats and AGEs: PUFAs Are Even Worse than Fructose

The Many Health Benefits of Rooibos Tea

Oxidation gives rooibos its familiar reddish colour. (Photo by Smaku)

The herbal tea made from rooibos has been a popular drink in Southern Africa for generations. The plant, Aspalathus linearis, is grown only in a small area in the Western Cape province of South Africa, but during recent years rooibos has become popular in other parts of the world as well.

Though not technically a tea, the infusion made from oxidised rooibos leaves is commonly referred to as rooibos tea. Traditionally, it is enjoyed hot with a slice of lemon and sugar or honey, but iced tea versions and even a rooibos espresso made from concentrated rooibos are apparently gaining popularity.

While many people have acquired a taste for rooibos and know that it is considered something of a health drink, most of us are clueless as to what exactly the health benefits of rooibos are. In this post, we'll review what the studies say on rooibos tea.

The antioxidant activity of rooibos tea

Like regular tea, rooibos tea contains flavonoids which act as antioxidants. While the most beneficial flavonoids of green tea are catechins such as epigallocatechin gallate (EGCG), the main flavonoids in rooibos tea are aspalathin and nothofagin. One in vitro study found that aspalathin is even more effective at scavenging free radicals than EGCG (link) – a rather surprising result, given that just about everyone knows about antioxidants in green tea but not in rooibos tea. All in all, green tea still seems to beat rooibos tea in antioxidant activity, however (link).

The second flavonoid tested, nothofagin, was not as effective as quercetin but still potent. Oddly enough, an older study found that aspalathin and nothofagin can also act as pro-oxidants under certain in vitro conditions (link). The authors comment:

Fermentation (i.e., oxidation) of rooibos decreased the pro-oxidant activity of aqueous extracts, which was contributed to a decrease in their dihydrochalcone content. The in vitro pro-oxidant activity displayed by flavonoid-enriched fractions of rooibos demonstrates that one must be aware of the potential adverse biological properties of potent antioxidant extracts utilized as dietary supplements.

This is not a unique case, however. Vitamin C, probably the most famous antioxidant, has also been said to act as a pro-oxidant in some conditions in vitro; there is much less evidence to suggest it does so in vivo, however (link).

Feeding normal, healthy rats given rooibos tea instead of water had significantly higher serum superoxide dismutase (SOD) levels than the control rats (link). They also had less DNA damage, a result that confirms the findings of an earlier study (link). Futhermore, when the rats were given dextran sodium sulfate to induce colitis, the rooibos group had higher SOD levels, and the drop in hemoglobin levels seen in the control group was prevented. Thus, rooibos tea seems to be anti-inflammatory and have the potential to prevent DNA damage.

The cardiovascular benefits of rooibos tea

Due to their effects on vasodilation and vasoconstriction, angiotensin I-converting enzyme (ACE) inhibitors and nitric oxide (NO) are used to treat conditions such as high blood pressure and heart failure. In one study, the effect of green tea, black tea and rooibos tea on ACE and NO was compared in healthy human volunteers (link). None of the three had a marked effect on NO concentration, but both green tea and rooibos tea inhibited ACE activity, suggesting that they have cardiovascular benefits. This is in contrast to an earlier in vitro study which found that only green tea and black tea inhibited ACE (link).

Closely related to cardiovascular disease is diabetes. The good news is that that rooibos tea may help with this as well. In a mouse model of type 2 diabetes, aslapathin suppresses the increase in fasting blood glucose levels. It also improves glucose tolerance, apparently through stimulating glucose uptake in muscle tissues and insulin secretion from the pancreas (link). Drinking rooibos tea during a meal may not be a bad idea.

Rooibos tea for liver disease and respiratory problems

In rats, rooibos tea aids in liver tissue regeneration after prolonged intoxication. Compared to the rats receiving water during the regeneration period, the rooibos group had less fibrotic tissue in their livers and lower tissue malondialdehyde levels. The authors conclude that rooibos tea "can be recommended not only for the prevention but also as a co-adjuvant for the therapy of liver diseases."

Rooibos tea also has therapeutic potential for respiratory ailments. According to a study on rats, in addition to lowering blood pressure, rooibos tea is both a bronchodilator and an antispasmodic (link, link). This helps explain why rooibos tea is commonly used for gastrointestinal and respiratory problems. The flavonoid chrysoeriol seems to be mainly responsible for the bronchodilator and antispasmodic effect.

Rooibos extract fights HIV

Rooibos tea extract seems to be helpful in antigen-specific antibody production by increasing interleukin-2 (IL-2) production in vitro and in vivo (link). According to the authors, rooibos tea intake "may be of value in prophylaxis of the diseases involving a severe defect in Th1 immune response such as cancer, allergy, AIDS, and other infections."

Another study found that an alkaline extract of rooibos tea leaves suppressed HIV-induced cytopathicity (link). Green tea extract, on the other hand, was ineffective. The authors conclude that HIV infection may be suppressed by the daily intake of the alkaline extract of rooibos tea. Note that the extraction mechanism is important here, because regular rooibos tea does not have anti-HIV activity (link). See the abstracts for details.

Rooibos tea, lipid peroxidation and brain aging

The uncontrolled oxidation of lipids, which can happen during cooking or inside the body, leads to the formation of advanced lipid peroxidation end-products (ALEs). The accumulation of such products is one of the types of damage that occurs with aging.

Lipid peroxides also accumulate in the brain. Rooibos tea may help prevent this damage, however. Rats given rooibos tea instead of water accumulate significantly less aging damage in the brain than rats given water (link). In fact, the 24-month old rats given rooibos tea for most of their lives had brains similar to young 5-week-old rats. This is quite a remarkable result.

One study found that out of the flavonoids tested, quercetin and EGCG (found in green tea) were the best inhibitors of lipid peroxidation, while aspalathin had a similar potency as catechin (link). Nothofagin was of no use here, however. Since polyunsaturated fats or PUFAs are especially prone to form ALEs, it seems like a cup of green tea or rooibos tea with a meal containing polyunsaturated fats might be useful.

The difference between red and green rooibos tea

Typically, rooibos leaves are oxidised before they are used to make rooibos tea. This process, which is not exactly the same as the fermentation process used in making black tea, gives them the familiar reddish-brown color and the slightly sweet taste. However, unoxidised rooibos tea is also available, if you know where to look. The color and taste are quite different; I personally prefer the red version, but green rooibos tea is not bad either.

Like in the case of regular tea, the oxidation process also affects the flavonoid content of the tea. Unoxidised rooibos tea contains more about twice as much total flavonoids as oxidised tea and 10-fold higher levels of aspalathin and nothofagin (link, link). In the studies that have directly compared the two, the unoxidised version seems to generally come out on top. For example, unoxidised rooibos tea seems to protect rats from liver cancer more effectively than oxidised tea (link). The antimutagenic activity of the two depends on the mutagen in question, however (link).

Summary

The health benefits of rooibos tea seem to be mostly due to the flavonoids aspalathin and nothofagin, although other compounds in rooibos may also play a part. Here's a summary of the benefits:

• Acts as an antioxidant and increases SOD levels
• Prevents DNA damage
• Cardiovascular protection through ACE inhibition
• Suppresses fasting glucose levels
• Improves glucose uptake and insulin secretion after a meal
• Aids in liver tissue regeneration
• Lowers blood pressure
• Acts as a bronchodilator and antispasmodic
• Inhibits lipid peroxidation and brain aging
• Rooibos extract improves immune defects such as HIV

Since nothofagin and especially aspalathin are not really found in any other plant, rooibos tea looks like a valuable addition to one's health regimen. Even people who are not fans of green tea usually like the taste of rooibos tea. Since rooibos contains no caffeine, it can be also enjoyed in the evening.

For more information on various teas and health, see these posts:

Hibiscus Tea Lowers Blood Pressure
Tea, Coffee and Cocoa: All Good for Your Teeth
Yerba Mate Inhibits AGE Formation
Drinking 3 Cups of Green Tea Increases Plasma Antioxidant Activity in Humans by 12%

Ashwagandha as a Nootropic – Experiment Begins

Ashwagandha, the 'Indian ginseng', shares some of the properties of Korean ginseng. (Photo by bartpogoda)

Ashwagandha is one of the plants used in Ayurvedic medicine. Also known as Indian ginseng, the scientific name of this nightshade family member is Withania somnifera. The latter part of the name means "sleep-inducing" in Latin, suggesting that the plant is used for its relaxing properties.

Ashwagandha is also said to be an adaptogen – a herb that increases the body's resistance to stress, anxiety and fatique by "normalizing" its functions. Before you dismiss the whole thing as new age garbage, let me point out that unlike some other Ayurvedic herbs, this one has been studied quite extensively. A pubmed search on 'ashwagandha' gives about 360 results.

Having browsed through the entire list, it appears that ashwagandha has a variety of effects on health. In this post, however, I will concentrate on the nootropic aspect of the herb. Bear in mind that I'm using the term in a very broad sense here: any paper examining the effect of the herb on cognition, mood, stress-relief, or motivation will be included. We'll save the studies on topics such as immune function for later.

The effect of ashwagandha on mood and libido

GABA, which is short for gamma-Aminobutyric acid, is the chief inhibitory neurotransmitter in mammals. GABA agonists – drugs that stimulate or increase the action at the GABA receptor – usually have a relaxing and stress-relieving effect. Alcohol is one such agonist. At least one paper has shown that ashwagandha contains an ingredient that activates the GABA receptor in a dose-dependent manner (link). Thus, the GABAergic activity may explain why many people report feeling more relaxed after taking ashwagandha.

GABA agonists are sometimes also used to treat psychostimulant addiction. Indeed, in animal models of drug addiction, ashwagandha apparently reduces alcohol intake and morphine tolerance (link). Ashwagandha itself appears to be well-tolerated: a review concluded that it has little or no risk of toxicity (link).

In a study that examined the role of stress in male infertility, 5 grams of ashwagandha root powder was given daily for 3 months to infertile men suffering from psychological stress (link). The treatment resulted in a decrease in stress levels and an increase in the level of antioxidants. At the same time, semen quality improved, which led to pregnancy in 14% of the subjects' partners.

Another study showed similar results, with reduced oxidative stress and improved sperm count and motility in infertile men (link). Testosterone levels increased significantly, while prolactin decreased. This is interesting, because prolactin counteracts the effect of dopamine. Dopamine is responsible for sexual arousal and motivation, while prolactin is thought to cause the sexual refractory period after an orgasm. High levels of prolactin cause impotence and loss of libido. The increase in testosterone and decrease in prolactin may therefore explain some of the claimed positive effects of ashwagandha on motivation and libido.

Some of the evidence on ashwagandha and libido is contradictory, however. When male rats were given 3,000 mg/kg of the root extract for 7 days, a marked impairment in libido, sexual performance, sexual vigour and penile function was seen (link). The authors state that since no change in testosterone levels was seen, the negative effects may be due to an increase in prolactin levels or the activity of GABA and serotonin. The increase in prolactin is interesting because it's opposite to what was seen in the study on humans. Note, however, that the dose used here was much higher than in the other rodent studies – perhaps the dose-response curve is U-shaped and more is not necessarily better.

Ashwagandha, stress and memory function

In mice, ashwagandha improves retention of a passive avoidance task (link). In this task, the mouse learns to refrain from stepping through a door to an apparently safer but previously punished compartment, which allows their memory to be assessed. The dosages used were 50, 100 and 200 mg/kg orally. The treatment also reversed the negative effects of scopolamine and electroconvulsive shocks on memory. Furthermore, mice and rats seem to do better on a forced swimming test when treated with ashwagandha (link, link).

Korean red ginseng, also known as Panax ginseng, is also called an adaptogen and shown to be helpful in treating stress. In a study comparing the two, both Panax ginseng and ashwagandha alleviated stress-related conditions such as sexual dysfunction, cognitive deficits and depression in mice subjected to footshocks (link). Ashwagandha was given orally in a dose of 25 or 50 mg/kg and was apparently more effective than Panax ginseng.

Acetylcholinesterase (AChE) is an enzyme that degrades the neurotransmitter acetylcholine, which is a facilitator of memory formation. AChE inhibitors increase the availability of acetylcholine, presumably leading to an improvement in memory. They can be extremely harmful in high doses: AChE inhibitors occur in natural venoms and poisons and are also used in nerve gases. However, AChE inhibitors are also used for medicinal purposes, for example to treat Alzheimer's disease. Huperzine A and galantamine, which are used for memory support and as nootropics, inhibit acetylcholinesterase. Ashwagandha appears to be an AChE inhibitor as well, with methanol extracts being more potent than water extracts (link).

In memory-deficient mice with neuronal atrophy and synaptic loss in the brain, withanolide A – an extract of ashwagandha – induced significant regeneration of nerve fibers and dendrites, as well as a reconstruction of pre- and postsynapses in the neurons (link). Treatment with the extract resulted in a reversal of the memory deficit. Two other extracts, withanoside IV and withanoside VI, appear to have similar effects (link). Ashwagandha or its extracts could thus be used to reconstruct neuronal networks.

Methanol extracts and withanolides are not the only useful part of ashwagandha, however. One study showed that even a withanolide-free water extract of ashwagandha roots had significant antistress activity (link).

Conclusion & my self-experiment

The evidence supports the claims that ashwagandha is an adaptogen and a nootropic. While there are no studies showing that ashwagandha improves mood per se, it does have a range of benefits.

The relaxing and anti-stress effect can be at least partly attributed to the fact that ashwagandha acts as a GABA agonist. It also improves stress-related memory problems by acting as a AChE inhibitor, and has the ability to prevent cognitive degeneration and even reconstruct neuronal networks.

Ashwagandha also seems to correct hormonal imbalances and reduced libido in men by increasing testosterone and decreasing prolactin. Very high doses may have the opposite effect, however.

For the purposes of my own human experiment, I have a bottle of NOW Foods' Ashwagandha extract. The bottle contains 90 capsules with 450 mg of root extract standardized to a minimum of 4.5% total withanolides. Once again, the measuring stick will be my own subjective evaluation of my mood, stress level and libido. Stay tuned for a conclusion of the experiment once I've finished the bottle.

Meanwhile, if you've tried ashwagandha, feel free to drop a comment about your experience. For more information on cognition, stress, mood and libido, see these posts:

Nootropic Battle Conclusion: Acetyl-L-Carnitine vs. Ginkgo Biloba vs. Taurine
Green Tea Protects from the Psychological Effects of Stress in Rats
The Effect of Maca Root on Energy and Libido – Experiment Conclusion
Caloric Restriction Improves Memory in the Elderly

Carotenoids and Lipid Peroxidation: Can Vegetables & Fruit Reduce ALEs?

Can we reduce ALEs by eating foods rich in carotenoids? (Photo by tibchris)

When you cook foods until they have that delicious brown color, what you're really seeing is advanced glycation end-products, or AGEs. In cooking, they're formed by heating sugars with fats or proteins, but they can also be formed inside the body through normal metabolism. The problem with AGEs is that with time, they accumulate in the body and cause harm.

Similar products are formed when polyunsaturated fats are oxidized, as a result of heating or contact with oxygen. These are known as advanced lipid peroxidation end-products, or ALEs. Lipid peroxidation is even more problematic than glycation, because it leads to ALEs much more rapidly than glycation leads to AGEs.

So what can we do to reduce the accumulation of ALEs? As we've seen, one obvious way is to avoid cooking with fats that contain lots of polyunsaturated fatty acids. Still, as in the case of AGEs, ALEs are formed not only on the frying pan but also inside the body as a result of metabolism. Since completely avoiding polyunsaturated fats is probably not feasible (and they may even have certain benefits), looking for ways to inhibit metabolic lipid peroxidation seems very useful.

In addition to fatty acids, other components of the diet play a role in the accumulation of AGEs and ALEs. One particular group of micronutrients that may be beneficial is carotenoids, the compounds which give vegetables and fruit their bright color. In this post, we'll take a look at what the studies say on carotenoids and lipid peroxidation.

Various carotenoids and lipid peroxidation

One study found that carotenoids inhibited lipid peroxidation in mouse embryo cells (link). The carotenoids tested were alpha-carotene, beta-carotene, canthaxanthin, lutein, lycopene, and bixin. Bixin, which is extracted from annatto seeds, was the most effective out of the six.

In another study, the effect of various carotenoids on lipid peroxidation were measured in membranes enriched with polyunsaturated fatty acids (link). Surprisingly, only astaxanthin reduced peroxide formation, while beta-carotene and lycopene increased it significantly. Zeaxanthin and lutein also increased peroxide formation slightly.

The authors of the second paper note that this may be because conventional antioxidant assays use high concentrations of free radicals over a period of a few hours, whereas this study observed the effects over a longer period (48 hours). The relevance to biological systems is not entirely clear, but these results might help explain some of the controversial effects of carotenoids (for example, beta-carotene increasing lung cancer risk in smokers).

Zooming in on lutein

While the above studies suggest that other carotenoids such as astaxanthin may be useful, many of the studies on lipid peroxidation focus mainly on lutein. One paper I've posted earlier about as part of my self-experiment claimed an improvement in skin elasticity, hydration and photoprotection from a supplement containing lutein. Interestingly, a reduction in lipid peroxidation was also seen.

In another study, when spinach or perilla preparations containing 5 mg lutein were given to healthy volunteers for 10 days, their plasma concentrations of lutein increased significantly (link). The increase was more pronounced after consumption of perilla, even though the amount of lutein in both preparations was the same. In other words, other micronutrients in the food in question have an effect on lutein absorption.

Glutathione peroxidase was unchanged, but superoxide dismutase increased slightly. Both of these enzymes protect the body from oxidative damage. As for lipid peroxidation, the concentration of malondialdehyde (MDA) in plasma tended to decrease and the time span until a rapid increase in oxidation (known as lag time) tended to increase after spinach and perilla. MDA is a product of lipid peroxidation which eventually forms ALEs.

It's interesting to note that while lutein is absorbed rather well from vegetable foods, it is also absorbed from carotenoid supplements. In fact, the bioavailability of lutein from vegetables is only 67% compared to a preparation of pure carotenoids (link). In contrast to some of the findings in other studies, in this study healthy volunteers fed a high-vegetable diet or given 9 mg lutein and 6 mg beta-carotene daily for 4 weeks did not show an increased resistance to LDL oxidation ex vivo. The authors suggest that one possible explanation is that while lutein and beta-carotene concentrations increased, plasma lycopene concentrations decreased on both diets.

In one human study on healthy men, subjects were first put on a low carotenoid diet and then given either 330 mL tomato juice, 330 mL carrot juice or 10 g spinach powder for 2 weeks to see how the diets affected LDL oxidation. This time it was tomato juice that reduced the lag time of lipoprotein oxidizability, while carrot juice and spinach powder had no effect (link). Glutathione peroxidase was again unchanged. Given that tomatoes contain both lutein and lycopene, perhaps this hints at some kind of a synergy between the two?

Finally, let's take a brief look at two studies suggesting that lutein might be useful in treating diseases related to lipid peroxidation.

Lipid hydroperoxides are non-radical intermediates of lipid peroxidation that are involved in many diseases. For example in dementia, the number of phospholipid hydroperoxides (PLOOH) in red blood cells is greatly increased. When six healthy subjects took 9.67 mg lutein daily for 4 weeks, PLOOH levels decreased in red blood cells (link). An antioxidant effect was confirmed in red blood cells but not in plasma.

Genetically modified mice (ApoE-/-) that have high cholesterol and develop atherosclerosis as a result. They also have increased levels of systemic and retinal lipid peroxidation compared to wild mice. Supplementing them with 0.09 mg/kg lutein per day protects their retinas from this oxidative damage (link), suggesting that lutein might be helpful for patients with hypercholesterolemia.

Conclusion

Carotenoids may be effective in reducing lipid peroxidation and thus the accumulation of ALEs. Lutein in particular seems useful: at doses of 5-10 mg per day, it has been shown to increase plasma levels of lutein and reduce some of the markers of lipid peroxidation. Other carotenoids, such as astaxanthin and bixin, may be beneficial as well.

It should be noted that some of the evidence is contradictory. Some studies have found no benefit, and one study even found a slight increase in lipid peroxidation from various carotenoids. A certain balance of carotenoids may be necessary for inhibiting the formation ALEs; lycopene in particular may be important.

For more information on AGEs, ALEs and aging, see these posts:

Sugar and AGEs: Fructose Is 10 Times Worse than Glucose
Eating Meat or Going Vegan? Comparing AGE Levels in Vegetarians and Omnivores
AGE Content of Foods
Green Tea Reduces the Formation of AGEs

5 Reasons Why Dark Chocolate Is Better than Milk Chocolate

Look good? Forget it, there's way too much sugar. (Photo by .craig)

You may have thought of chocolate as a guilty pleasure, but the ancient Maya considered it the food of gods.

Granted, the Maya also thought cutting out someone's heart in a ritual ceremony was a good fun, but they did get one thing right: chocolate really is a health food. That is, as long as you buy the dark kind. In fact, the darker the chocolate the healthier it is. As good as that sugar-laden milk chocolate bar may taste, it wouldn't have made its way into any self-respecting Maya feast.

If you don't believe me, read further for three good reasons to choose dark chocolate instead of milk chocolate.

1. Dark chocolate is better for weight loss.

Even though the amount of calories in milk chocolate and dark chocolate are pretty similar (and in fact milk chocolate sometimes contains fewer calories), dark chocolate contains significantly less carbohydrates. Milk chocolate usually has about 50 grams of carbs per 100 g, while the amount of carbs in dark chocolate ranges from 8 to 35 carbs, depending on how dark it is. A chocolate with 70% cocoa has ~30 grams; a 85% chocolate has ~20 grams.

If weight loss or maintenance is your goal, the combination of large amounts of carbohydrates and fat is something to avoid. A high carbohydrate load will increase insulin secretion, which is a signal for the body to store energy as fat. The reason why low-carb diets are so effective for weight loss is their effect on insulin: even if you eat lots of fat, if there are no carbs present to drive insulin up, the energy from dietary fat won't be stored into fat cells.

Unless you consume only a small quantity or restrict other carb sources to a minimum, combining milk chocolate with a low-carb diet is going to be difficult. If your goal is to stay under 50 grams per day, 100 grams of milk chocolate fills up your entire quota. But 100 grams of 85% dark chocolate still leaves you with 30 grams to spend on other carb sources, making dark chocolate a viable option even for low-carb dieters.

2. Dark chocolate causes less aging.

Okay, so perhaps a bit of an exaggeration there, since we don't know exactly how big a role advanced glycation end-products play in the aging process. We do know, however, that the accumulation of AGEs is one of the seven biomarkers of aging, which makes avoiding them a sensible goal.

As it happens, weight gain is not the only problem with the carbs in milk chocolate. Almost all of the carbohydrate in chocolate is sucrose, which is half glucose and half fructose. Even though the word 'glycation' in 'AGE' implies that glucose is the culprit, the fact is that fructose is much more prone to cause AGEs in the body. Since the main ingredient in milk chocolate is sugar, a 100 grams of milk chocolate will also give you a hefty dose of fructose.

Dark chocolate, on the other hand, is mostly composed of fat – cocoa butter, to be specific. The fatty acid composition is 61% saturated fat, 36% monounsaturated and only 3% polyunsaturated fat, making cocoa butter very resistant to oxidation. And if you're worried about cholesterol, here's something to ease your mind: almost all of the saturated fat in cocoa butter is cholesterol-neutral stearic acid. Fructose, however, may increase triglycerides levels.

Unlike dark chocolate, milk chocolate also contains some lactose. In addition to making milk chocolate an impossible treat for some lactose intolerants, lactose also causes glycation. Lactose breaks down to glucose and galactose, and like fructose, galactose appears to form AGEs more rapidly than glucose.

3. Dark chocolate has more cocoa polyphenols.

The health benefits of chocolate are almost entirely due to the polyphenols found in cocoa. As a rule of thumb, whenever you read something good about chocolate, what they're really talking about is cocoa. Therefore, as the cocoa content of chocolate increases, so do its positive effects on health. A standard milk chocolate will contain about 30% cocoa, while premium dark chocolates usually have more than 70%.

Another thing that reduces the polyphenol content of chocolate (by 60-90%) is alkalization (link), also known as Dutch processing or simply Dutching. Alkalization was invented in the 19th century to get rid of some of the bitterness of cocoa powder and to make it more palatable. Non-alkalized cocoa powder is a more light brown in color and tastes less sweet than alkalized cocoa powder.

Nowadays Dutch processing is very common among industrial chocolate makers (link), which suggests that there's a good chance the average high-sugar milk chocolate will contain alkalized cocoa. Many dark chocolates seem to use non-alkalized cocoa, however, probably because the bitterness is perceived as preferable among chocolate enthusiasts.

4. The cocoa polyphenols in dark chocolate are more bioavailable.

Even if your dark chocolate happens to be made from alkalized cocoa, you'll still get more bang for your buck in terms of polyphenols, because the polyphenols will be more bioavailable. This is again related to differences in the macronutrient composition of chocolates.

First, the bioavailability of cocoa polyphenols depends partly on the fat content of chocolate. One in vitro study showed that cocoa liquor (which is about 50% fat) retained more polyphenols than cocoa powder (about 15% fat) when submitted to a digestion model (link). The reason appears to be that the higher fat content increases the stability of cocoa polyphenols during digestion. Second, sucrose and milk protein may affect the absorption of polyphenols negatively (link).

Dark chocolate contains no milk protein, less sucrose and much more cocoa liquor than milk chocolate. The actual content varies, since different countries have different regulations on what kind of chocolates can be called "dark chocolate". The FDA, for example, states that dark chocolate must contain at least 35% chocolate liquor, while milk chocolate only needs to have more than 10%.

Also, chocolates with 40-70% cocoa are also sometimes sold as "dark chocolate", so be sure to check the ingredient list before purchase. The words "cocoa mass", "cocoa liquor", "cocoa powder", "cocoa paste", "cocoa solids", or something to that effect should be first on the list – if "sugar" is mentioned first, it's definitely not real dark chocolate.

5. Dark chocolate is more filling.

Anyone who has tried both milk chocolate and dark chocolate must have noticed that it takes much less to satisfy chocolate cravings with the latter than the former. I can personally eat 200 grams of milk chocolate (more than 1,000 kcal) in one go without having my craving satisfied. With 99% dark chocolate, a few pieces is enough. A similar effect was shown in a study from last year (link).

This, as mentioned before, is not related to energy content, because milk chocolate and dark chocolate have virtually the same amount of calories. Rather, the reason why a smaller quantity of dark chocolate is enough is probably a combination of less sugar and more nutrients. Humans generally have a preference for sweet foods, which is why we love candy when we're kids. But part of the reason why we can't stop eating candy until we feel sick is that there are no nutrients in candy, only calories. This lack of nutrients causes our body to send the satiety signal way too late.

Since dark chocolate is higher in cocoa powder, it's also higher in many nutrients, such as iron, magnesium, phosphorus, copper and manganese. Combined with the lower amount of sugar and high amount of fat, it's no surprise you get your daily chocolate fix quicker with dark chocolate than milk chocolate.

Summary

Dark chocolate contains less sugar, more cholesterol-neutral fat, and more cocoa polyphenols in a more bioavailable form than milk chocolate. Dark chocolate is also more filling, which means it takes less calories to satisfy your chocolate cravings.

Keep in mind, however, that excess consumption of dark chocolate has its downsides too. Cocoa powder is high in iron and oxalates, which are harmful in high quantities. We'll return to the subject of optimal intakes in future posts, but for now, I limit mine to 50-100 grams of chocolate per day.

For more information on chocolate, sugar, fat, and health, see these posts:

Tea, Coffee and Cocoa: All Good for Your Teeth
SAs, MUFAs vs. PUFAs: Fat Storage Depends on Type of Fatty Acid in Rabbits
Fats and AGEs: PUFAs Are Even Worse than Fructose
Low-Carb vs. Low-Fat: Effects on Weight Loss and Cholesterol in Overweight Men

Green Tea Protects from the Psychological Effects of Stress in Rats

Feeling stressed? Enjoying a cup of green tea with your lunch may help. (Photo by chotda)

It's no secret that a cup or two of green tea can make you relaxed, but now scientists have shown that green tea can reduce the effects of psychological stress in rats.

In a paper yet to be published, rats were put under stress and given either their usual diet or a diet enriched with green tea polyphenols (link). To see how psychological stress and green tea were related, experiments measuring cognitive performance and serum levels of stress hormones were done.

Study method

The rats were divided into five groups: control group (CT), stress group (ST), and three stress groups given low, medium and high doses of green tea polyphenols (LG, MG and HG). The green tea polyphenol (GTP) content of the three diets were 0.1%, 0.5% and 1%, respectively.

Psychological stress was induced by keeping the rats restrained and inhibiting their movements six hours every day for three weeks. Their cognitive performance was then evaluated using an open-field test, a step-through test and a water maze. These tests measure both the activity level and memory ability of rats.

Green tea polyphenols and cognitive performance

In the open-field test, which measures how actively rats explore the arena, the stressed rats were much less active than the control rats. No significant improvement was seen in the rats fed the low dose of green tea polyphenols, while the rats given the medium or high dose were almost as active as the control rats.

The memory of the rats was also affected by stress during the step-through test and water maze test. These tests measure spatial memory and the ability to remember adverse stimuli. Again, only the medium and high doses of GTPs significantly reduced the harmful effects of stress on the rats' memory.

Green tea polyphenols and stress hormones

Stress activates the symphatetic nervous system, which results in a release of catecholamines. Catecholamines are "fight-or-flight" hormones that consist of epinephrine, norepinephrine and dopamine. They are involved in the modulation of cognition, awareness, attention, and emotional state, helping the body to cope with a stressful situation. According to the authors, when the stress level is too high for the body to cope with, cognitive impairments appear and the levels of these hormones begin to decline.

Plasma levels of norepinephrine (another stress hormone, also known as noradrenaline) and dopamine were remarkably reduced in the ST and LG rats. In the MG and HG groups norepinephrine and dopamine levels were lower than in the control group, but much higher than in the LG group. In other words, medium and higher levels of green tea polyphenols partially inhibited the stress-induced decrease in the levels of these hormones.

All four stress groups had higher levels of plasma cortisol than the control group. Cortisol is often referred to as the "stress hormone", since its levels increase in the presence of stress and anxiety. Cortisol also causes blood pressure to rise and immune responses to be reduced. Feeding the stressed rats green tea polyphenols lowered their cortisol levels, but the reduction was statistically significant only in the MG group.

The levels of reactive oxidative species (ROS) were increased in the brain tissue of stressed rats, but again, medium and high doses of GTPs partially inhibited this increase. Similarly, the total antioxidative capacity in brain tissue was reduced by stress but to a smaller extent in the MG and HG groups. The levels of superoxide dismutase showed a similar trend, but the differences were not statistically significant.

A different effect was seen in the levels of interleukin-6 and interleukin-2. While stress increased IL-6 and IL-2, feeding the rats GTPs did not inhibit this increase. In fact, green tea polyphenols increased IL-6 even further. This may be because increased levels of IL-6 can enhance the body's adaptability to stress. Similar effects have been reported in other studies on green tea.

Conclusion

Psychological stress negatively affected the behavior and memory of rats. This adverse effect was associated with higher levels of cortisol, reactive oxygen species, IL-2, and IL-6, and lower levels of norepinephrine, dopamine, and total antioxidative capacity.

These changes were partially inhibited by diets containing 0.5% and 1% green tea polyphenols, except for IL-6, which was further increased by GTPs. A diet containing only 0.1% GTPs did not show significant results.

For more information on green tea and cognition, see these posts:

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