L-cystine

Cystine is a sulfur amino acid that is formed by two cysteine molecules. It is the main component of keratin, which is a fibrous protein that is part of the hair, skin and nails. Cystine deficiency, generally caused by unbalanced or restrictive diets (weight loss diets, vegetarian, vegan, etc.) can lead to hair deterioration and hair loss and, in addition, to the loss of nail strength and elasticity. Studies of orally administered L-cystine show that sulfur amine is involved in the synthesis of hair keratin and has also been shown to be associated with an increase in hair density.