L-cysteine plays an important role in keeping the overall hair health. L-cysteine is one of few amino acids that has the ability to form disulfide bonds in the body. These disulfide bonds hold together the keratin strands within the hair, which provide the hair with its fibrous properties that hold on to moisture and prevent hair dryness. Also, L-cysteine directly helps in maintaining the texture and thickness of hair.
The hair consists of three layers: the cuticle, cortex and medulla. The outer layer – the cuticle – surrounds the inner layers of the cortex and the medulla. The medulla in its turn is also surrounded by the cortex, and is present right at the center of the hair shaft. The medulla is responsible for the natural hair thickness through genetic signaling.
The most prominent of these layers is the middle one; the cortex. It makes up almost 80 – 90% of a single strand of hair. The cortex is abundantly supplied with keratin molecules bundled together that give strength to the hair follicles. Each bundle of this fibrous filament structure contains almost 75% of L-cysteine. Many topical hair care products such as hair oils and shampoos contain L-cysteine as a major ingredient. The L-cysteine will maintain and promote the keratin and disulfide bond formation.
Also, in case of L-cysteine deficiency due to decreased absorption from the gastrointestinal tract, or decreased dietary intake, oral supplements of L-cysteine are available to help restore its normal levels in the body. Foods that are high in L-cysteine include soybeans, beef, lamb, sunflower seeds, cheese, oats and chickpeas.