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

    January 2019 in “ Journal of cosmetology & trichology ”
    Vincenzo Nobile, Joel Duperray, Enza Cestone, Renaud Sergheraert, Francesco Tursi
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    Studysummary In this study, researchers found that supplementation with L-cystine, either alone or with a keratin hydrolysate, significantly improved hair density, hair and nail brightness, and nail growth in women experiencing acute telogen effluvium and brittle nail syndrome over three months. Our plain-language summary of this paper — not a Tressless recommendation.
    In a 2019 randomized, placebo-controlled clinical trial involving 60 healthy female subjects with acute telogen effluvium and brittle nail syndrome, researchers found that L-Cystine (CYS) alone or in combination with a natural keratin hydrolysate (Kera-Diet® or KDC) significantly improved hair density, hair and nail brightness, and nail growth rate over a 3-month period. The study reported a 56.9% and 58.9% increase in hair brightness for the CYS and KDC groups, respectively, and a nail growth rate of 0.21 ± 0.02 mm/14 days for the KDC group after 90 days. The treatments were well tolerated with no adverse reactions, and a self-assessment questionnaire indicated a 90% global satisfaction rate for the combination treatment. The study concluded that both L-Cystine and the combination with Kera-Diet® are effective and safe for improving hair and nail parameters in healthy females, offering a beneficial dietary approach for managing symptoms of acute telogen effluvium and brittle nail syndrome.
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