Synopsis

Source of validity: Scientific
Rating (out of 5): 2

Cystine is a sulfur-containing amino acid that is formed by the oxidation of two cysteine molecules. It is found in keratin, the structural protein that makes up hair, nails, and the outer layer of skin. The rationale for using cystine to support nail health is based on its role as a building block of keratin. Several studies have examined the role of cystine (often in combination with other nutrients such as biotin, zinc, and B vitamins) in improving nail strength and reducing brittleness. However, direct evidence for cystine supplementation alone significantly improving nail health in healthy individuals is limited. Most research has focused on combination products or on populations with certain deficiencies. In vitro studies and biochemical knowledge support the idea that adequate cystine is necessary for keratin synthesis, which is important for healthy nails. Nonetheless, robust, large-scale clinical trials directly demonstrating its efficacy as a supplement for nail health are lacking. Therefore, while there is a scientific rationale and some supportive data, the clinical evidence is not strong. The use of cystine for nail support is more justified by our understanding of biochemistry than by comprehensive clinical validation.

More about Cystine
More about Nails

Other ingredients that support Nails

Other body systems supported by Cystine

Products containing Cystine