What is “Sarcosine” and what is its purpose?

The sarcosine is a natural amino acid derived from glycine, of which it is both an intermediate and a by-product. It is produced from glycine by the enzyme glycine-N-methyltransferase and reconverted into glycine by sarcosine dehydrogenase. It also occurs as a step in the metabolism of choline and methionine, two nutrients rich in methyl groups that are essential to numerous biochemical reactions. Rapidly degraded into glycine, sarcosine contributes indirectly to the synthesis of key compounds such as glutathione, creatine, purines and serine. In healthy adults, its average blood concentration is around 1.4 ± 0.6 μM. In cosmetics, it is often used in its free form or, more frequently, as acylated derivatives, such as sodium lauroyl sarcosinate, an amphiphilic molecule used in cleansing products, hair care formulations or foaming gels.

In the laboratory, it can be obtained fromchloroacetic acid and methylamine, whereas on an industrial scale, it is produced by Strecker synthesis. This chemical method consists of reacting three components: an aldehyde , which is an organic molecule containing a carbonyl group, cyanide, which provides a source of nitrogen and carbon, and ammonia , which is also a source of nitrogen. These reagents first combine to form an intermediate compound called an α-aminonitrile, which is then converted (hydrolysed) into an amino acid, such as sarcosine.

The sarcosine has attracted growing interest because of its potential regulatory effect on sebum production, which would make it a particularly relevant active ingredient for targeted scalp care. Sarcosine is a derivative of glycine and is involved in certain metabolic pathways related to amino acids and lipids, which is why some researchers and formulators have hypothesised that it could influence enzymes associated with lipid metabolism, such as 5α-reductase, through metabolic modulation or interaction with its cofactors.

Sebum, produced by the sebaceous glands, plays an essential role in protecting andhydrating the skin and the scalp, but its excess can lead to imbalances, promoting the appearance of problems such as excessive shine, dandruff or inflammation. Sarcosine is thought to act by modulating the activity of certain key enzymes involved in lipid synthesis, in particular 5α-reductase-1, an enzyme known to catalyse the conversion of testosterone into dihydrotestosterone (DHT). This active hormone is known to stimulate excessive sebum production under certain conditions. By inhibiting or regulating this enzyme, sarcosine would thus help to reduce excessive sebaceous secretion, thereby helping to restore an optimal skin balance.

However, the scientific literature does not demonstrate any direct link between sarcosine and sebum regulation.

Indirectly, its potential sebum-regulating property could also lead to a prebiotic effect, illustrated by the concept of a "scalp microbiome reset", which consists in restoring a healthy scalp microbiota through recolonisation by six beneficial bacterial strains (Staphylococcus pasteuri, S. warneri, Streptococcus australis, Rothia aeria, Veillonella parvula, Actinomyces odontolyticus). Indeed, by reducing excess sebum, sarcosine could modify the cutaneous ecosystem and deprive lipophilic micro-organisms such as Cutibacterium acnes of their main source of nutrients. This would limit their proliferation and free up space for other commensal species, thereby promoting greater microbial diversity.

To sum up, sarcosine could act simultaneously on lipid homeostasis and on microbiota balance, creating a more stable cutaneous environment, less prone to inflammation and favourable to the coexistence of beneficial strains.

However, studies are required to confirm the role of sarcosine in regulating sebum production, as well as its effects on the balance of the microbiota.

Sarcosine is also an interesting ingredient, as it may help toenhance the penetration of active compounds into the skin. Indeed, a study published in the Journal of Controlled Release in 2013 explored new transdermal penetration enhancers based on amino acids modified with hydrophobic chains via a labile ester linkage. Among these, sarcosine (N-methylglycine) stands out because of its polar head and its low ability to form hydrogen bonds, which promotes its insertion into the lipids of the stratum corneum. This insertion disrupts lipid organisation, increases membrane fluidity, and facilitates the passage of active substances through the skin. Tests have shown an efficacy comparable to or greater than certain conventional enhancers, with low toxicity and a reversible effect, making it an attractive candidate for improving the cutaneous delivery of medicinal agents or cosmetic actives.

Regarding its security profile, sarcosine and its derivatives have been the subject of several rigorous assessments. The Cosmetic Ingredient Review (CIR) published a report in 2001 on acyl sarcosines and sarcosinates, concluding that these ingredients are safe for cosmetic use at typical concentrations: up to 5% for leave-on products and up to 12% for rinse-off products. No irritating, sensitising or mutagenic effects were detected in in vitro or in vivo tests, according to the CIR Final Report. However, a warning is issued regarding the possible formation of N‑nitrososarcosine, a potentially carcinogenic nitrosamine, if sarcosine is formulated with nitrosating agents (such as nitrites). This risk is well known, strictly regulated under European legislation (Regulation (EC) No 1223/2009), and avoided by formulators by excluding any nitrosamine precursors.

• LANIGAN R. S. Final report on the safety assessment of cocoyl sarcosine, lauroyl sarcosine, myristoyl sarcosine, oleoyl sarcosine, stearoyl sarcosine, sodium cocoyl sarcosinate, sodium lauroyl sarcosinate, sodium myristoyl sarcosinate, ammonium cocoyl sarcosinate, and ammonium lauroyl sarcosinate. International Journal of Toxicology (2001).

• KELLER D. & al. Investigation of the skin-sensitising properties of 5 osmolytic prodrugs in a weight-of-evidence assessment, employing in silico, in vivo and read-across analyses. International Journal of Toxicology (2012).

• VAVROVA K. & al. Amino acid derivatives as transdermal permeation enhancers. Journal of Controlled Release (2013).

• HELDRETH B. & al. Revised safety assessment of fatty acyl sarcosines and sarcosinate salts as used in cosmetics. International Journal of Toxicology (2021).

• HUANG Z. & al. The impacts of sodium lauroyl sarcosinate in facial cleanser on the facial skin microbiome and lipidome. Journal of Cosmetic Dermatology (2024).