 We're kicking off a three video series on hair loss. What causes it? And what can drug supplements and foods do to help prevent or reverse it? Watch the videos to find out. I know I'm going to. 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 little to the many myths out there. The majority of hair loss with age is genetic for both women and men in the case of this study. Based on twin studies, the heritability of baldness in men is 79%, meaning about 80% of the difference 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. For example, check out these two identical twin brothers, same genes, but the twin on the right reported more stress in their life. In this pair, the identical twin on the right was a smoker and drank more alcohol. Smoking can contribute to the development of both male and female pattern baldness because of 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. Women of reproductive age frequently seek treatment for what is thought to be hormone-related hair loss, especially at menopause. But for example, this woman came in with hair loss and blood tests indicated elevated mercury levels and no wonder as she had a diet high in tuna. But the good news is that her mercury levels fell, with elimination of dietary tuna. Within two months, her hair started to come back in seven months, maintaining a fish-free diet. Her hair completely re-grew. 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 in uncovered 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? For 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're 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 are in 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. 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. 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. 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. Also the tests 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 manufacturers 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.