Graying hair is a sure-fire sign of aging. But what is going on? Actually, the hair is being bleached. Recently-reported research indicates that graying with age is due to a buildup of hydrogen peroxide in human scalp hair shafts – yes the same stuff used to bleach hair. The peroxide blocks synthesis of our hair’s natural pigment, melanin. The buildup of hydrogen peroxide is caused by a reduction of an enzyme that converts hydrogen peroxide into water and oxygen, and the graying is compounded by low levels of methionine sulfoxide reducase (MSR) A and B, enzymes that repair hair follicles. Further, these events disrupt the formation of tyrosinase, a key enzyme involved in the production of melanin.
What can be done about all this to bring back naturally-colored hair? That is unclear for now but there are hints. It appears that a key step in the sequence of hair-bleaching events, oxidation of methionine sulfoxide, can be blocked in-vitro by L-methionine. Methionine is an amino acid that can be found in sesame seeds, Brazil nuts, fish, meats, and certain plant seeds. L-methionine is also readily available as a dietary supplement. Taurine, an amino acid derivative from L-methionine and cysteine metabolism, and also available a dietary supplement, also seems to have a protective effect on human hair follicles in-vitro(ref). However, so far I have seen no research evidence that dietary L-methionine or taurine can have any impact on human hair color or density.