Soy Isoflavones Reduce DHT, Increase Testosterone

Soybeans contain the isoflavones genistein and daidzein. (Photo by T. Hagihara)

There's a lot of speculation on how soy intake and hair growth are related, so in a series of posts beginning with this one, we'll be taking a look at what the studies have to say. Hopefully, it will become clear whether soy isoflavones really do anything, how much isoflavones is the optimal intake, and whether oral or topical is the way to go.

In the first study we'll look at, male rats were fed soy isoflavones in various amounts (link). After a week, their testosterone and dihydrotestosterone (DHT) levels were measured. Since reducing DHT levels seems to be an effective way to reduce hair loss, this should be an interesting study for people considering soy isoflavones as a remedy.

Composition of the soy diets

To find out how soy isoflavones and androgen levels are related, the authors conducted two experiments. In the first experiment, rats in the treatment group were given soy flour with their normal chow. In the second experiment, rats in the treatment groups were given either a soy methanol extract or semipurified soy isoflavones.

The isoflavone content of the soy flour was 1.92 mg/g. The isoflavone contents of the soy methanol extract and semipurified soy isoflavones were 3.38 mg/g and 218 mg/g, respectively. In the first experiment, the rats in the treatment group received 442.7 g/kg soy flour in their diet. In the second experiment, they received 20 g/kg of soy extract or 2 g/kg of soy isoflavones in their diets.

Long story short, the according to the authors, the actual soy isoflavone intakes of the rats were as follows: 19 mg/day in the soy flour group, 0.9 mg/day in the soy extract group, and 3.3 mg/day in the soy isoflavone group. The control groups consumed zero soy isoflavones.

Soy isoflavones and DHT

Rats on the soy flour diet had significantly lower DHT levels than rats on the control diet. Similarly, the DHT levels of the rats on the soy isoflavone diet were about 60% lower DHT than in the control group. On soy extract diet DHT levels tended to decrease, but the difference was not statistically significant.


The figure above shows the DHT levels for the soy extract and soy isoflavone diets compared to the control group. The observed decrease in DHT from the soy flour diet (not shown above) was similar to that of the soy extract diet, with the exception that the difference was statistically significant.

Soy isoflavones and testosterone

Rats on the soy flour diet had similar levels of testosterone + dihydrotestosterone (T+DHT) as the control group. Since their DHT levels were lower, however, this means that there was an increase in testosterone from eating the soy flour diet. In the soy isoflavone diet, this effect was even clearer; not only was the reduction in DHT balanced by an increase in testosterone, but the total T+DHT levels were much higher than they were before the diet.



The figure above shows the T+DHT levels of the soy extract and soy isoflavone diets compared to the control group. Testosterone levels tended to increase and DHT levels tended to decrease also on the soy extract diet, but again, the differences were not statistically significant.

The fact that the soy isoflavone showed significant effects and the soy extract is possibly due to the differences in soy isoflavone content of the diets. The rats on the soy extract diet consumed only 0.9 mg/day, while those on the isoflavone diet consumed 3.3 mg/day. The two graphs shown here seem to support the idea that the effect is dose-dependent.

What is confusing, however, is that the soy flour diet showed a less pronounced effect than the soy isoflavone diet even though it had a much higher isoflavone content. Perhaps the dose-response is not linear but a bell curve. Unfortunately, the authors offer no explanation or theory for the results in the paper.

Conclusion

Soy isoflavones significantly reduced DHT levels and increased testosterone levels in male rats. An intake of 3.3 mg of isoflavones per day was the most effective of the three treatments tested. A lower intake showed similar but less pronounced effects, while a higher intake did not appear to further add to the effect.

For more information on hair growth, see these posts:

Tea Tree Oil vs. Korean Red Ginseng – Hair Growth Battle Conclusion
North African Plant Extract (Erica multiflora) Increases Hair Growth
Bioactive Form of Silicon (BioSil) Improves Skin, Hair & Nails in Photoaged Women
2% Nizoral Shampoo Increases Hair Growth More than 2% Minoxidil

Yerba Mate Inhibits AGE Formation

Yerba mate contains caffeic acid, which inhibits glycation. (Photo by MaPev)

Advanced Glycation End products (AGEs) are formed in two ways: outside the body and inside the body. The former happens when sugars are heated with fats or proteins, the latter through metabolism when eating glycation-prone foods such as fructose.

From an anti-aging point of view, reducing the formation of AGEs is important. One way of doing it is to avoid cooking as much as possible. However, since the idea of never eating a fried steak is less than appealing to many, including me, I'm constantly on the lookout for foods and supplements that may help reduce AGEs.

One natural way to inhibit AGE formation is to drink green tea, which has been shown to reduce AGEs both in vivo and in vitro. However, it seems that there's a better anti-glycation drink available: yerba mate.

Infusions of yerba mate (Ilex paraguariensis) are especially popular in South America, but it's becoming increasingly known in other places as well. I've drank yerba mate on and off for years simply because I like it, but this is the first time I've come across it's effects on AGEs. I assume that as we learn more about its benefits, it will be even more popular among health-conscious people. Now, let's look at the study.

Reducing AGE formation: yerba mate vs. green tea

The authors of the paper (link) compared the AGE-inhibiting effect of yerba mate to that of green tea and aminoguanidine, a known anti-glycation agent. Water extracts of normal strength were used for green tea and yerba mate (5 g and 10 g leaves / 2 dl water, respectively). Bovine serum albumin and methylgloxal were used to generate AGEs on proteins in vitro.

As expected, high doses of aminoguanidine reduced both indicators of glycation (tryptophan fluorescence and AGE fluorescence) by more than 90%. The surprise is that yerba mate dose-dependently and significantly reduced AGE fluorescence, while green tea showed only a non-significant positive trend. At the highest dose (20 mcl/ml), the inhibition from yerba mate reached 40%.

How and why does yerba mate inhibit AGEs?

Glycation is really a process with several steps, which eventually leads to the formation of AGEs. Aminoguanidine prevents the first reaction in glycation and thus all its downstream effects from occurring. Yerba mate, on the other hand, works differently. It inhibits the second phase of glycation: the conversion of Amadori products to AGEs. According to the authors, this is likely due to the antioxidant and free radical quenching capability of yerba mate.

One possible explanation for yerba mate beating green tea is that yerba mate naturally contains more polyphenols than green tea. Also, the infusion of yerba mate in the study was stronger than the green tea infusion. A more convicing explanation is that the bioactive substances between the two are different. While most of the benefits of green tea are due to its catechins, yerba mate contains caffeic acid, chlorogenic acids, saponins and sapogenins.

Another study (link) compared the effects caffeic acid, a chlorogenic acid (5-caffeoylquinic acid) and a sapogenin (oleanolic acid) on AGE formation. Out of the three, caffeic acid was most effective and oleanolic acid was the weakest in inhibiting glycation. Importantly, caffeic acid and chlorogenic acid inhibited glycation even more effectively than aminoguanidine, with caffeic acid inhibiting 95% of AGE formation.

How much yerba mate do I need to drink, then?

The important question, of course, is whether drinking yerba mate can really prevent AGEs in the human body. To get some idea of what the answer might be, let's look at some of the figures.

The yerba mate extract used in the study was not especially strong: 10 grams of leaves per 2 desiliter of water heated to 90 °C. This makes for a stronger infusion than green tea, but since the taste of yerba mate is not as strong, 10 grams is very close to how you would normally drink it. The polyphenol content of the infusion was 2.6%.

According to the authors of the first paper, a significant effect was seen in vitro at a concentration of the extract that corresponds to a 1:100 dilution of the preparations usually drunk, which suggests that a high bioavailability may not be needed. The authors of the second paper note that the concentrations of oleanolic acid may mimic those found in humans.

So, even though we don't have enough data at this point to make more than educated guesses as to much yerba mate consumption really helps with reducing AGEs, drinking a few cups of yerba mate with AGE-containing meals may not be such a bad idea.

Conclusion

Yerba mate reduces glycation in vitro by inhibiting the conversion of Amadori products to AGEs. The most potent substances found in yerba mate were caffeic acid and chlorogenic acid, which were more effective than aminoguanidine (an anti-glycation drug) in inhibiting AGE formation. The amount of yerba mate needed to see anti-AGE benefits in humans is unclear, however, because no studies on humans exist.

For more information on glycation and aging, see these posts:

Green Tea Reduces the Formation of AGEs
Intermittent Fasting Reduces Mitochondrial Damage and Lymphoma Incidence in Aged Mice
Anti-Aging in the Media: 60 Minutes on Resveratrol
How the Accumulation of Minerals Might Cause Aging in Humans

Office Politics

There is just too much apathy when it comes to office politics these days. Someone should really look into it. Maybe some of the great professors of political science and behavioral psychology can figure out how to solve this pressing problem.

BCS for Basketball

Did I hear right? Is it true that the NCAA is so pleased with the wonderful BCS system for football that they are now doing it for basketball too? No more long, drawn out tournament—just a bunch of "bowl" games, with one of them serving as the national championship game. I guess today they'll be announcing these bowl games instead of the brackets.

I hope the rumor is true because March Madness is just too boring.

Spring Broke

This week was "Spring Break" at the University of South Carolina, meaning there were no classes, but I knew I would still need to get some a lot of work done. So, as for "Spring Break," let's break it down:

Spring: This week was definitely spring-like with temperatures in the 70s here in Columbia, perfect for some bike rides and baseball.

Break Broke: It wasn't really much of a break. But it should have been. I was beat at the start of the week. I should have gotten out for a round of golf, a movie, something fun. Instead, I tried to work but that didn't work very well. Then Jacob got sick on Wednesday, so I stayed home and Lauren's school was closed on Friday so I had a fun day with her (including lunch with Jacob--she loves pretending that she's already a Kindergartner). But I didn't get to mark much off of my to-do list.

I think we need to take the time to refresh the body and spirit and pay the price when we don't. I should have been more intentional and taken some time to clear my head, and then I would have likely been more productive the rest of the time.

Lesson learned (I hope).