Among the most talked-about ingredients in hair supplements, cysteine holds a special place: it isn't just a trendy ingredient, but a structural component of hair itself.
An Amino Acid at the Heart of Keratin
Hair is made up of more than 90% keratin, a protein rich in sulphur-containing amino acids, including cysteine. It's cysteine that forms disulphide bonds — the chemical bonds that give the hair shaft its strength and elasticity. Without a sufficient supply of cysteine, keratin synthesis can be limited.
Where Cysteine Comes From
The body can synthesise some cysteine from another amino acid, methionine, supplied by diet (meat, eggs, legumes, whole grains). In the case of an unbalanced diet or increased needs, supplementation can make sense.
What the Studies Suggest
Several studies have looked at the value of cysteine supplementation, alone or combined with other nutrients (zinc, B vitamins), on the quality and strength of the hair shaft. The available results are encouraging for hair strength, particularly when initial intake is insufficient, but should be interpreted with caution: hair responds to many combined factors, and no single ingredient ever explains everything.
In Practice
Cysteine is most valuable when combined with other nutrients involved in hair growth, rather than used alone as a miracle solution. That's why it's most often found in combined formulas rather than as a standalone supplement.
Find cysteine combined with other key nutrients in our Vibrant Hair Vitamins — the full formula is available on our Ingredients page.
This article is provided for informational purposes only and is not a substitute for personalised medical advice. If in doubt, consult a doctor, dermatologist, or pharmacist.