L-cysteine: the main hair growth-stimulating amino acid

A description is provided below of the characteristics of this amino acid that is basic for the health of our hair.

L-cysteine is a non-essential a-amino acid that contributes to protein production in the body. In order to cover daily needs, it is advisable to consume food supplements, since L-cysteine is directly formed from L-methionine, which is an essential amino acid obtained from food.

What is the role of L-cysteine?

The body converts ingested L-cysteine into a potent antioxidant that protects the cells from free radicals and the side effects of reactions to medicines or toxic chemical products. This amino acid is a building block of proteins that are used throughout the body. One such protein is hair keratin. Cysteine constitutes approximately 10-14% of the skin and hair. It is therefore essential for the body to have the necessary amounts of this amino acid to preserve both general health and skin and hair consistency.

Scientific basis: cysteine and hair loss

Recent studies have suggested that a diet poor in cysteine, or health problems resulting in deficient cysteine absorption in the body, are among the main causes of hair loss. The amount of cysteine present in the hair fibre is an indicator of hair health (Structure and expression of genes for a class of cysteine-rich proteins of the cuticle layers of differentiating wool and hair follicles. (1990). The Journal of Cell Biology, 111(6), 2587–2600). Likewise, in conjunction with other amino acids and proteins, cysteine protects the hair and feathers of animals and contributes to establish mechanical resistance (Strasser B, Mlitz V, Hermann M, Tschachler E, Eckhart L. Convergent evolution of cysteine-rich proteins in feathers and hair. BMC Evolutionary Biology. 2015;15:82). This potent amino acid is regarded as one of the main factors implicated in hair growth.

A study conducted in the Department of Health Sciences of the University of Genoa showed that L-cysteine is a key component of hair that plays a role in alopecia - capable of influencing the mechanisms implicated in hair loss. Following a previous study on the tobacco-mediated generation of alopecia in mice, the investigators also carried out a study in mice exposed to a smoking machine. The groups of mice received three dosing levels of L-cysteine and vitamin B6 a day. Vitamin B6 was used due to its important role in the incorporation of L-cysteine to ciliated cells. After 6 months of exposure, the results showed that the mice administered the highest doses of L-cysteine and vitamin B6 suffered much less hair loss. The authors therefore concluded that the oral administration of L-cysteine and vitamin B6 is effective in preventing alopecia (D'Agostini F., Fiallo P., Pennisi T., De Flora S. Chemoprevention of smoke-induced alopecia in mice by oral administration of L-cysteine and vitamin B6. Journal of Dermatological Science, Volume 46, Issue 3, June 2007, Pages 189-198, ISSN 0923-1811).

Likewise, another study conducted in the Department of Pharmacy of the University of Naples showed that L-cysteine prevents diminished keratin synthesis induced by iron deficiency in human keratinocytes. This study showed that L-cysteine promotes keratin regulation in de novo protein synthesis and counters the adverse effect of iron deficiency (Miniaci, M.C., Irace, C., Capuozzo, A., Piccolo, M., Di Pascale, A., Russo, A., Lippiello, P., Lepre, F., Russo, G. and Santamaria, R. (2016). Cysteine prevents the reduction in keratin synthesis induced by iron deficiency in human keratinocytes. J. Cell. Biochem).

On the other hand, a document on the evidence-based guidelines referred to the treatment of alopecia in both men and women (Blumeyer A., Tosti A., Messenger A., Reygagne P., Del Marmol V., Spuls P., Trakatelli M., Finner A., Kiesewetter F., Trüeb R., Rzany B., Blume-Peytavi U. Evidence-based (S3) guideline for the treatment of androgenetic alopecia in women and in men. J Dtsch Dermatol Ges. 2011 Oct.; 9 Suppl. 6:S1-57) conducted an in-depth evaluation of several amino acids, with special mention of cysteine, which was described as the main amino acid implicated in hair growth. The document cites a study (Morganti P., Fabrizi G., James B., et al. Effect of gelatin-cysteine and Serenoa repens extract on free radicals level and hair growth. Journal of Applied Cosmetology, 1998;16:57-64) in which a very significant change was observed in the mean total hair count in men and women following a treatment containing cysteine. The participants received an oral supplement containing cysteine, copper, zinc and histidine four times a day during 50 weeks. The results of the study by Morganti et al. in relation to the influence of cysteine upon hair growth were very promising: 48 volunteers between 21 and 38 years of age participated in the study, and 12 received a cysteine-based dietetic supplement, as well as a solution based on Serenoa repens - also known as saw palmetto.

One of the groups received both ingredients (cysteine and saw palmetto), while the control group only used a lotion. At the end of the 50 weeks of treatment, a 20-30% increment in hair mass was observed, with an increase of up to 27% in the number of hairs. The group that also received the dietetic supplement containing cysteine, copper, zinc and histidine showed a 50% increase in hair growth.

Since its creation, REDENHAIR has developed product lines with these combinations of nutrients. One of them comprises supplements for the prevention of hair loss - REDENHAIR HAIR NUTRITION SUPPLEMENT - while another consists of the REDENHAIR ANTI-HAIR GREYING supplements. Although the functions and aims of these two lines differ, the combination of these ingredients proves effective in combating alopecia and the appearance of grey hair. In addition to the core formulation, these products also include key nutrients for hair, such as folic acid, zinc and copper, among others.

In sum, research warrants the effectiveness of certain nutrients not only in stimulating healthy hair growth but also in reducing hair loss. Nevertheless, a guaranteed continuous and constant supply is crucial, since our hair only grows at a rate of approximately 1 centimetre a month, and never stops growing. We therefore recommend the dietetic supplements REDENHAIR HAIR NUTRITION SUPPLEMENT to prevent hair loss and stimulate strong and healthy growth, and REDENHAIR ANTI-GREY HAIR to prevent loss of natural hair colour and the appearance of new grey hairs.