Tuesday, June 29, 2010

Soy Isoflavones Grow Hair by Increasing IGF-1 in the Skin

Food sources of isoflavones include tofu and miso soup.
Food sources of isoflavones include tofu and miso soup. (Photo by sokole oko)

Many of you have probably heard that soy isoflavones may be good for hair loss. How exactly dietary isoflavones work to promote hair growth is less clear, however.

As long-time readers may remember, I've written before about the effects of dietary isoflavones on humans and animals. For example, in male rats even a relatively low amount of soy isoflavones reduces DHT and increases testosterone. This alone would probably be enough to explain hair growth in rodents.

Of course, humans are a more difficult case. Most of the things that show promise in mice or rats don't work for humans with androgenic alopecia in the end. The good news is that soy isoflavones reduce DHT even in humans. The bad news is that the reduction may not be great enough. About 60 mg of isoflavones daily reduced serum DHT in healthy young men by only 15%.

Even this moderate drop would suggest a reduction in 5-alpha-reductase, which converts testosterone to DHT. However, the markers of 5-alpha-reductase looked at in the study did not show a difference between the treated and the control group.

And yet, a combination of capsaicin and soy isoflavones grows hair in both animals and humans. In this study, capsaicin injected into the skin was enough to grow hair in animals, although the combination was more effective. In humans, orally administered isoflavones and capsaicin resulted in hair growth in 88% of the participants with androgenic alopecia, which is a remarkable result for a supplement that reduces DHT by so little.

The authors speculated that capsaicin and soy isoflavones promote hair growth by increasing dermal levels of insulin-like growth factor (IGF-1). They suggested that a key factor was calcitonin gene-related peptide (CGRP), which acts as a vasodilator, among other things. It also increases IGF-1 in various tissues, including the skin.

This theory is supported by the fact that subcutaneous capsaicin increased CGRP release and IGF-1 expression in hair follicle cells in normal mice but not in CGRP-knockout mice. Soy isoflavones increased the production of CGRP, which explains why the combination was more effective than capsaicin alone.

Based on these studies, it was still unclear whether dietary isoflavones alone promote hair growth. Now, the same authors have investigated their idea further. In their new study, they fed isoflavones to mice whose backs were shaved and measured their hair growth (link). Again, both wild-type mice and CGRP-knockout were used.

The isoflavone supplement used was Fujiflavone P40, which contains 43.5% isoflavones. 5 g of the product was mixed per each kg of standard chow. On average, the mice ate 4.6 grams of food daily, which means that their daily intake of isoflavones was 0.0046 * 0.005 * 0.435 = ~10 mg (correct me if my calculation is wrong).

After three weeks of isoflavone administration, dermal CGRP and IGF-1 levels in wild-type mice increased significantly compared to the control group. In the knockout mice, no difference was seen between mice given isoflavones and the control group.

Hair follicle number also increased in wild-type mice given isoflavones. Compared to the control group, they had about 40% more hair follicles. The knockout mice had less hair follicles to begin with, and when they were given isoflavones, no improvement was seen. Thus, it seems that isoflavones grow new hairs through increasing dermal levels of CGRP and IGF-1.

Compared to the mice given isoflavones, the control mice seemed to take a longer time growing their existing hair back. Even the knockout mice that saw no increase in IGF-1 grew their hair back quicker when they were given isoflavones. This might be due to other effects of isoflavones, such as reducing DHT levels. Based on the pictures in the full paper, the wild-type mice grew their hair back even quicker, however. Wild-type mice given isoflavones also had a more pronounced darkening of hair than their control group.

So what is the take home message? Based on all these studies, it looks like soy isoflavones show very good potential for promoting hair growth. A part of their effectiveness may come from the fact that they reduce serum DHT and increase testosterone, but based on the rodent data, the real kick is from the increase in skin levels of IGF-1.

At the moment, there is no data comparing the effectiveness of soy isoflavones vs. capsaicin in humans. However, we do know that the combination is superior in increasing dermal IGF-1 in animals, and that the combination of both taken orally grows hair in humans with androgenic alopecia.

For more information on hair growth, see these posts:

Topical Retinoids Increase Hair Growth in Most People
BioSil, JarroSil & Beer – Silicon Experiment Conclusion
Zinc Pyrithione Reduces Shedding and Moderately Promotes Hair Growth
Hair Growth with Ayurveda – The Nutrich Oil Experiment

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10 kommenttia:

Maharishi June 29, 2010 at 9:01 PM  

Thanks for another very interesting post. I discovered your blog a couple of months ago and read nearly every posting. Just wanted to let you know I appreciate your effort.

Jared Bond June 30, 2010 at 2:06 PM  

Hey, I remember IGF-1 being accused for making the eyeballs grow longer than they should be, thus causing nearsightedness; any thoughts?

JLL June 30, 2010 at 7:03 PM  


Thanks, I'm glad you like it!

FrF July 1, 2010 at 9:18 PM  

I completely agree with Maharishi. Inhuman Experiment is a very interesting resource. I'm always learning something new :-)

(I didn't even know about soy isoflavones and capsaicin prior to reading about them at IE!)

JLL, do you also keep an eye on hair multiplication and its protagonists like Follica and Histogen? What do you think about this line of research? Apart from corporate news (i.e. it getting additional funding) there hasn't been much heard from Follica but Histogen made headlines recently with this study:


All in all I think there's a reasonable chance that we'll get rid of the scourge that is MPB within the next, say, ten years. Let's not use the proverbial five-year time frame, though of course that would be even better :-)

JLL July 1, 2010 at 9:28 PM  

@Jared Bond,

I've never heard of that. Any studies on that claim?


I wrote an article on Intercytex and regenerative hair therapy some time ago on tressless.com. I do believe that things like Follica and Histogen may be effective treatments one day, but I don't write about them so much, because I focus on writing about things that can be done by anyone at home -- which pretty much rules out injectable treatments.


FrF July 1, 2010 at 9:49 PM  

Oh, sorry, JLL, I completely forgot that you're occasionally writing for Tressless.

Now I remember reading that article about Intercytex, thinking, "That's a well-written piece" and then I saw your initials in the byline.

The patient pictures in your older article* about soy isoflavones and capsaicin are actually rather encouraging. Now I understand why you're making a multi-part series about this type of treatment :-)


E July 2, 2010 at 5:57 AM  

Hey JLL,
I just recently found your blog in the past week or so and have read a substantial amount of your posts due to the fact that they are quality and give a good perspective on topics people are interested in.

So I've read that soy isoflavones can interact with finasteride so I don't think I will want to take those (maybe too much anti dht supplements can be a problem? I don't know). I can search for the site I read that on if needed.

So my question to you is what supplements/topicals do you think are best for hair growth/regrowth in your experience and research?

I'm interested in toco-sorb and capsaicin, gingko, all kinds of stuff.

This page is pretty interesting on the topic btw (its a good site);


JLL July 2, 2010 at 11:35 AM  


Finasteride, minoxidil and ketoconazole are probably the most effective ones. Then there's piroctone olamine, which is similar to ketoconazole. Vitamin A derivatives such as retinol and retinoids also have studies behind them, and I saw some new hairs from using a topical retinol cream.

I tried toco-sorb for a month but didn't see anything. I took ginkgo too, but that was for a nootropic experiment. No effects from that either.

My suspicion is that a green tea cream at the right concentration would probably be a pretty good topical. That combined with oral soy isoflavones, capsaicin, and flax meal might be a good "natural" regimen. Those are the most promising ones, at least.

Most likely anything that reduces inflammation is good in the long run, too.

Anonymous July 15, 2010 at 4:26 AM  

@ E:
Could you please show a link to a study/article that speaks out about interaction between finasteride and soy isoflavones?
What would they be?
Harmful to health, halting their effect each other or just doubling the effect on the other hand, or unexpected long term endocrinological effects?
Thanks in advance!

Anonymous December 14, 2010 at 12:55 PM  

So does isoflavones work by increasing levels of IGF-1 in the body, or by allowing more IGF-1 to accumulate at the scalp by increasing vasodilation and thus blood flow to the scalp?

I heard that IGF-1 is not good if you have cancer or tumor risks, as it increases proliferation of such tissue. But if it is working mainly by vasodilation via CGRP then it would be a lot safer.


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