Preventing Hair Loss

I’m often asked my opinion about a diet or a disease is. Who cares what my or anyone else’s opinion is? All we should care about is what the science says. What does the best available balance of evidence published in the peer-reviewed medical literature have to say right now?

Welcome to the NutritionFacts Podcast – I’m your host Dr. Michael Greger.

Did you know that by age 50 – about half of all men and women will experience hair loss? The majority of age-related hair loss is genetic, but even identical twins can have dramatically different heads of hair depending on their diet and lifestyle.

In our first story, we look at whether biotin or zinc supplements prevent hair loss in men and women.

“Studies show that by age 50, approximately half of men and women will experience hair loss.” No, it’s not caused by washing your hair too much, or brushing your hair too much––two of the many myths out there. The majority of hair loss with age is genetic for both women and men. Based on twin studies, the heritability of baldness in men is 79 percent, meaning about 80 percent of the differences in hair loss between men is genetically determined. But that still leaves some wiggle room.
Even if you have identical twins––identical twin sisters in this case, with the same DNA––one can have more hair loss than the other, thanks to increased stress, increased smoking, having more children, or having a history of high blood pressure or cancer.
Smoking can contribute to the development of both male and female pattern baldness because the genotoxic compounds in cigarettes may damage the DNA in hair follicles, and cause microvascular poisoning in the base of the follicle. Other toxic agents associated with hair loss include mercury, because it seems to concentrate about 250-fold in growing scalp hair. In fact, maybe the reason Shakespeare started losing his hair was due to mercury poisoning from syphilis treatment. Thankfully, doctors don’t give people mercury anymore. These days, as the CDC points out, mercury mainly enters the body through seafood consumption.
So, doctors should consider screening for mercury toxicity when they see hair loss, since there’s something we can do about it. Instructing patients to reduce fish intake and repeat blood tests could offer relief of symptoms, and uncover dietary habits that may be a source of heavy metal-induced hair loss. Though admittedly, sometimes heavy metal can lead to too much hair.
What about nutrient deficiencies as a cause of hair loss? After bariatric surgery, the most frequent nutrient deficiency symptom is hair loss. But that’s because they’ve had their anatomy rearranged to cause malabsorption on purpose. In general, there is little evidence to suggest that vitamin and mineral supplementation benefits people, unless they are actually deficient.
For example, we’ve known for centuries that scurvy, severe vitamin C deficiency, can cause hair loss, but once you have enough vitamin C such that your gums aren’t bleeding, there’s no data correlating vitamin C levels and hair loss once you have a certain baseline sufficiency of vitamin C.
It’s also a myth that supplements containing zinc will increase hair growth––unless you have zinc deficiency, like if you’re an alcoholic or something. But if you have normal zinc levels in your blood, taking more zinc won’t help, and in fact can have negative side effects. It’s the same thing with taking iron supplements.
The most common ingredient in top-selling hair loss products is vitamin B7, also known as biotin. Yes, biotin deficiency causes hair loss, but there are no evidence-based data that supplementing biotin promotes hair growth. And severe biotin deficiency in healthy individuals eating a normal diet has never been reported. But if you eat raw egg whites, you can acquire a biotin deficiency, since there are these compounds that attach to biotin and prevent it from being absorbed. But other than rare deficiency syndromes, it’s a myth that biotin supplements increase hair growth.
But hey, why not just have the attitude, ‘‘Can’t hurt, might help?” Because of the lack of regulatory oversight of the supplement industry and, in the case of biotin, interference with lab tests. Many dietary supplements promoted for hair health contain biotin levels up to 650 times the recommended daily intake of biotin. And excess biotin in the blood can play haywire on a bunch of different blood tests, including thyroid function, and other hormone tests (including pregnancy), and the test they do to see if you’ve had a heart attack––so, it could potentially even be life or death.
And in terms of poor regulation, as I’ve done tons of videos about, there are all sorts of supplement manufacturer shenanigans. For example, this outbreak in which hundreds suffered selenium toxicity because they had an oopsie, and put 200 times the dose, and so, it ended up causing hair loss. And the same thing can happen with getting too much vitamin A.
Next up – we look at the pros and cons of the drugs finasteride and minoxidil for hair loss.

“Any consumer looking on the Internet for a treatment for hair loss is exposed to a multitude of remedies.” However, we only have good evidence for efficacy for the FDA-approved drugs: finasteride, sold as Propecia, and minoxidil, sold as Rogaine. It’s considered a myth that all the patented hair-loss supplements on the market will increase hair growth. And they may actually be more expensive, with over-the-counter supplement regimens costing up to more than $1,000 a year, whereas the drugs may cost only $100 to $300. The drugs can help, but can cause side effects. The Propecia can diminish libido and cause sexual disfunction, while the topical Minoxidil can cause itching.
To understand why there are so many hormonal side effects for Propecia, like impotence, testicular pain, and breast enlargement, you have to understand how the drug works.
Androgens––male hormones like testosterone––are the principal drivers of hair growth of men and women. We know this from studies a half century ago that show that castration of men stopped hair loss. Why exactly were they being castrated? It was due to eugenics laws in the United States, when mentally handicapped persons were castrated or had their tubes tied against their will. So-called retarded persons were routinely sterilized without their consent or knowledge and we, the United States of America, were the first country to introduce eugenic laws, which were later upheld by the U.S. Supreme Court. In the 1930s, a vocal proponent complained that “The Germans are beating us at our own game.”
Anyway, testosterone is the primary androgen circulating in the blood, and can be converted to dihydrotestosterone, which is even more powerful, by an enzyme called 5-alpha reductase. That’s the enzyme that is blocked by Propecia; so, it inhibits the souping up of testosterone. That’s why women are not supposed to take it––since it could feminize male fetuses, whereas for men, it has the sexual side effects like erectile dysfunction, which can affect men for years. It’s something the drug companies had to disclose for the last decade: “a difficulty in achieving an erection that continues after stopping the medication”––side effects that may even be permanent. Up to 20 percent of subjects reporting persistent sexual dysfunction for six or more years after stopping the drug, suggesting the possibility that it may never go away.
What we think might be happening is that the drug may actually structurally change the part of your brain responsible for sexual function. And indeed, though blood levels of hormones in users with persistent effects appear normal, if you do a spinal tap and look at the cerebrospinal fluid surrounding their brains, neurosteroid levels do appear to end up being altered. So, “[i]t is recommended that prescribers of finasteride, as well as potential users, be aware of the potential serious long-term risks of a medication used for a cosmetic purpose.”
To date, no new interventions are used routinely in the treatment of male or female pattern baldness. Given the side effects of the current drug options, there is a need for alternative treatments. So, what about foods? Things we could eat to combat hair loss. That’s exactly what we’re going to explore next.

Finally today – we take a look at some foods that may help with hair loss: hot peppers, soy foods, and pumpkin seeds.

Androgenic or androgenetic alopecia, also known as male or female pattern hair loss, is one of the most common chronic problems seen by dermatologists. Wait: so, it’s called male pattern hair loss and female pattern hair loss? Yeah, in men, they call it male pattern hair loss, and in women, they call it female pattern hair loss. Okay. Either way, it is characterized by progressive hair loss, predominantly of the central scalp. I’ve talked about hair-loss supplements. I’ve talked about hair-loss drugs. What about foods for hair loss? What role might diet play in the treatment of hair loss?
Human experiments with fecal transplants offer a clue to how powerful our microbiome is, with reports of improvements in hair loss after a fecal slurry made from freshly-passed stools from a donor was administered into another person’s colon, and not just by a little. A totally bald guy starts growing back hair a few months after a fecal transplant, and a little over a year later––completely regrown. The moral of the story is not to drink brown smoothies, but to keep your good gut bugs happy.
Population studies have found that male pattern baldness is associated with poor sleeping habits and the consumption of meat and junk food, whereas protective associations were found for the consumption of raw vegetables, fresh herbs, as well as the frequent consumption of soy milk. Drinking soy beverages on a weekly basis was associated with 62 percent lower odds of moderate to severe hair loss, raising the possibility that there may be compounds in plants that may be protective.
Complementary and alternative medicine treatments “boast the ability to ’cure’ hair loss ‘safely’ with ‘less side effects’ than conventional medicine. However, it is important…to look beyond the overarching claims and marketing to critically review the literature.” For example, many studies have little relevance because the evidence was obtained on shaved rodents. Hey, let’s smear shaved mice with bee venom. And even when they do clinical studies on actual people, sometimes there’s no placebo control; so, you have no idea if the food had anything to do with it.
But there has been a randomized double-blind, placebo-controlled study of compounds in hot peppers and soy, showing significantly higher promotion of hair growth. Okay, but what kind of doses were they using? They used 6 mg of capsaicin a day, and 75 milligrams of isoflavones. Okay, what does that translate out to in real food? You can get 6 mg of capsaicin in just a quarter of a fresh jalapeno pepper a day. That sounds pretty doable. And you can get 75 mg of isoflavones eating ¾ of a cup of tempeh, or just straight soybeans. Soy nuts (dry-roasted soybeans) are even more concentrated, but given the formation of advanced glycation end-products in high fat/high protein foods at high temperatures, I’d suggest avoiding routinely eating roasted or toasted nuts, seeds, or soy.
There’s also been a randomized, double-blind, placebo-controlled trial of pumpkin seed oil. Where did they get that idea? In 2009, a study out of South Korea found that randomizing men with BPH—enlarged prostate glands—to just 320 mg of pumpkin seed oil a day (that’s about a 16th of a teaspoon; so, just a few drops a day) improved urinary flow rates. Urinary flow continued to kink off and decline in the control group, but those taking the equivalent of just like eating two single pumpkin seeds a day saw a significant improvement. That would seem to be an anti-androgen effect; so, maybe it would help with hair loss.
It seems to work in mice when used topically, but what about in people just eating pumpkin seeds? It couldn’t hurt. Sadly, we often throw away pumpkin seeds, squash seeds, or watermelon seeds, and they actually have a rich repertoire of nutrition. But you don’t know if they actually work for hair loss, until you put it to the test.
76 men with male pattern baldness received 400 mg of pumpkin seed oil a day hidden in capsules, or they took placebo capsules for a few months. Again, that’s only like eating two pumpkin seeds a day––maybe two and a half pumpkin seeds. They measured scalp hair growth with all sorts of objective and subjective measures, and…after 24 weeks of treatment, self-rated improvement and satisfaction scores in the pumpkin seed oil group were higher, and they objectively had more hair, a 40 percent increase in hair counts, compared to only 10 percent in the placebo group.
In the pumpkin group, 95 percent remained either unchanged or improved, whereas in the control group, more than 90 percent remained unchanged or worsened. Given such a pronounced effect, might we be worried about sexual side effects. They looked before and after at an index of erectile dysfunction and found no evidence of adverse effects.

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