Evidence supporting the use of: L-methionine
For the health condition: Hair (loss or thinning)

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Synopsis

Source of validity: Scientific
Rating (out of 5): 2

L-methionine is an essential amino acid involved in a variety of metabolic processes, including the synthesis of proteins and the production of important molecules such as S-adenosylmethionine (SAMe), which plays a role in methylation reactions in the body. Methionine is sometimes included in dietary supplements marketed for hair health and the treatment of hair loss or thinning. The rationale is that methionine contributes sulfur to keratin, the main structural protein in hair, and that adequate methionine may be important for maintaining healthy hair growth.

However, while there is a plausible biochemical rationale for its inclusion and some limited laboratory evidence suggesting that methionine deficiency may negatively affect hair structure, robust clinical evidence in humans is lacking. Most of the support for methionine in hair loss treatment comes from its role as a sulfur donor in keratin synthesis and from animal studies or biochemical extrapolation. There are no large, high-quality randomized controlled trials directly demonstrating that methionine supplementation alone reverses or prevents hair loss in humans. Some evidence exists for formulas containing several amino acids, but this does not isolate the effect of methionine.

In summary, the use of L-methionine for hair loss or thinning is based on scientific reasoning and limited preclinical evidence, but direct clinical validation is weak. Thus, while its use is justified scientifically, the strength of supporting evidence is low (rated 2 out of 5).

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