Summary: Occasionally, women who become vegetarian or vegan report experiencing hair loss. If there is a dietary cause, the most likely are rapid weight loss, thyroid problems, or iron deficiency (although this has more recently been questioned; see below). Zinc deficiency and not getting enough of the amino acid lysine could also be culprits.
Hair loss among women is not an unusual problem. In one study, 34% of women from Japan, the USA, and the UK reported increased hair loss compared to 5 years earlier. The reasons for hair loss are complicated and can vary from person to person. Thus, it is important to see a doctor who can diagnose the specific problem.
In some cases, hair loss can be diet-related. Hair loss sometimes occurs in rapid weight loss. In one study, hair grew back within a few months after weight loss. In other cases, there are less obvious nutritional reasons for hair loss.
According to Mayo Clinic, an overactive or underactive thyroid gland can lead to hair loss. Upon going vegetarian or vegan, people might increase their soy intake. Soy can affect the thyroid, especially when iodine levels are not adequate or someone is predisposed to thyroid problems. Making sure you get enough iodine, by taking 75 to 150 µg per day from a supplement, should prevent any hair loss problems that could be due to iodine or soy. If you are predisposed to thyroid problems, limiting soy might also help.
In 2002, Dr. DH Rushton, of the University of Portsmouth in the UK, wrote a comprehensive review article on hair loss, a summary which follows (1).
Hair loss can be divided into two categories: Hair loss with skin shedding (also called "scaling") and hair loss without skin shedding. Hair loss with skin shedding is likely related to a skin disorder. In some cases, supplementation with the vitamin biotin (1 - 2 mg for 2 months) has helped. Essential fatty acids (omega 3s and/or omega 6s) might also help in hair loss caused by skin conditions.
There is a lack of objective data about hair loss without skin shedding. At one time, there was a widespread belief that zinc deficiency is a common cause. However, zinc supplementation has not been shown to improve hair loss, even when a deficiency is suspected. One area that seems clear is that iron deficiency (a low serum ferritin without anemia) is linked to hair loss in women. In one study, 72% of women with low iron stores (a serum ferritin less than 40 mcg/l) had reduced hair density.
The amino acid L-lysine plays a part in the absorption of iron and zinc. Among plant foods, L-lysine is only found in high amounts in legumes, and a vegan who doesn't eat many legumes could find themselves falling short on lysine. In some women, iron supplementation does not lead to an increase in iron stores. But in one study, adding L-lysine (at 1.5 - 2 g/day for 6 months) to iron supplementation in such women did increase iron stores and decreased hair loss by one half.
Dr. Rushton noted the following odds and ends:
- In a multivitamin, if the level of zinc is equal to the level of iron, then iron uptake is significantly decreased. A ratio of 3 to 1, iron to zinc, is desirable to prevent competitive interference.
- Excessive vitamin E supplementation (for example, 600 IU per day for 1 month) can adversely affect hair growth. In patients with hair loss who show high levels of folic acid (also known as folate), excessive folic acid supplementation should probably be discontinued.
- Reducing the frequency of shampooing does not help preserve hair and can increase the fear of hair loss because a higher amount of hair will be lost all at once when it is washed.
Although studies looking at iron deficiency in women with hair loss have been somewhat mixed, a 2010 well-controlled study found no difference in rates of iron deficiency or anemia between women with hair loss and controls (2). It is possible that iron deficiency plays a role in hair loss for some women, but it is unlikely to be a primary cause in most cases.
1. Rushton DH. Nutritional factors and hair loss. Clin Exp Dermatol. 2002 Jul;27(5):396-404. | link
2. Olsen EA, Reed KB, Cacchio PB, Caudill L. Iron deficiency in female pattern hair loss, chronic telogen effluvium, and control groups. J Am Acad Dermatol. 2010 Dec;63(6):991-9. Epub 2010 Oct 13. | link