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.