Efficacy and Safety of L-Cystine Associated or not to a Natural Keratin (Kera-Dietandreg;) Hydrolysate on Hair and Nails: Randomised, Placebo-Controlled, Clinical Trial on Healthy Females

Background: The acute Telogen Effluvium (aTE) and the Brittle Nail Syndrome (BNS) are two medical conditions affecting both males and females. A dietary approach based on aminoacids and/or on protein hydrolysate could be a safe and effective approach in reducing hair loss during acute telogen effluvium and in improving brittle nails conditions.Objective: In this study, we investigated the efficacy of L-cystine (CYS) associated or not to a commercially available hydrolysate (KDC) of natural keratin obtained from a non-human source (feathers) in improving both aTE and BNS symptoms.Design: A randomised, parallel group study was carried out for 3 months on 60 female subjects with aTE and BNS. Each subject attended clinic visits at the time of randomization (baseline) and after 45 and 90 days of products use. Anagen/Telogen hair, hair density, pull test, global photography, hair and nail brightness, and nail plate growth rate were measured. At the end of the study, a self-assessment test was carried out.Result: A statistical significant increase of hair density, hair and nails brightness, and nail plate growth rate were observed both in the CYS and KDC treatment group.Conclusion: This study demonstrates that L-Cystine alone or a mix Kera-Diet®+L-Cystine, associated with traced elements and specific vitamins at the right dosage can enhance hair and nails conditions, even though human nutrition is more and more balanced.