Keratin Peptides

Keratin in its native form is heavily cross-linked through disulfide bonds and is extremely poorly digestible. Hydrolyzed keratin peptides are produced by chemical or enzymatic processing that breaks the protein down into smaller, more soluble fragments (often referred to commercially as low molecular weight peptides). After oral ingestion, these peptides are further digested into individual amino acids and small di- and tripeptides, which are absorbed and used like any other dietary protein. The rationale for keratin peptide supplementation is that it provides the amino acid building blocks (notably cysteine, methionine, glutamic acid, and arginine) that the body uses to synthesize its own keratin in hair follicles and nail beds. Some manufacturers also claim that specific bioactive peptide fragments survive digestion and exert direct signaling effects, but this is not well established. A small number of manufacturer-funded human trials report improvements in hair tensile strength, shine, and nail growth, but independent replication is limited.

There is no established required intake. Commercial supplements typically provide 250 to 1,000 mg of hydrolyzed keratin per day, often combined with biotin, zinc, and other co-factors. DSLD label data are too sparse to derive a meaningful median dose.

Keratin peptides can be taken at any time. Like other protein supplements, they may be marginally better absorbed when taken with food, though this is not a major factor. Effects on hair and nails, if any, take months to become visible because of the slow growth rate of these tissues.

Hydrolyzed keratin is generally well tolerated. It is a protein source and would contribute the same risks as any other animal-derived protein, including potential allergic responses. Most supplement preparations are derived from sheep wool or poultry feathers; people with severe allergies to those source materials should avoid the product.

No significant pharmacological interactions are reported. As with any high-protein supplement, very large doses could theoretically affect protein-bound drug pharmacokinetics, but this is not clinically described for keratin peptides.