Synopsis

Source of validity: Scientific
Rating (out of 5): 3

Amino acids are the building blocks of proteins, including keratin, which is the primary structural component of hair. The scientific justification for using amino acids to support hair health, and potentially treat hair loss or thinning, rests on their essential role in hair growth and maintenance. Several studies have shown that deficiencies in certain amino acids—such as cysteine, methionine, lysine, and arginine—can negatively affect hair growth. For instance, cysteine is a key component of keratin, and its supplementation has been associated with improved hair strength and growth in some clinical and laboratory studies. Additionally, some over-the-counter hair growth supplements contain amino acids, and a few randomized controlled trials have found that combinations of amino acids, vitamins, and minerals may improve hair density and thickness in people experiencing hair thinning.

However, the evidence is not consistently robust. Most research involves multi-ingredient supplements rather than isolated amino acids, making it difficult to attribute effects specifically to amino acids. Moreover, in individuals without a deficiency, supplementation may not produce significant benefits. Overall, amino acids have a plausible biological mechanism and some clinical backing, warranting a moderate evidence rating, but more large-scale, high-quality trials are needed to fully validate their effectiveness for hair loss and thinning.

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Other health conditions supported by amino acids

Products containing amino acids

Douglas Laboratories Free Form Amino