Why Amino Acids Matter for Hair Growth

Hair is around 95% keratin, a structural protein — which means the raw materials for healthy hair are, quite literally, amino acids from your diet.

The three amino acids that matter most

L-Cystine forms disulfide bonds, the chemical "cross-links" that give each hair strand its strength and structure — it's a major reason why severely low-protein diets are associated with brittle, weaker hair. L-Lysine and L-Methionine are essential amino acids (your body can't produce them, so they must come from food or supplementation) that support keratin production and are involved in transporting other hair-supporting minerals like zinc.

How a shortfall shows up

You don't need a clinical deficiency to notice an effect — chronically low protein or amino acid intake, restrictive dieting, and high stress periods are all commonly linked to increased shedding and slower-feeling growth, even in people who otherwise eat "enough" food overall.

Why patience is part of the science

Hair grows in cycles: an active growth phase (anagen) that can last years, followed by a resting and shedding phase. Because each strand is on its own timeline, changes in nutrition typically take 8 to 12 weeks — sometimes longer — before they're visible at the surface. That's not a marketing caveat, it's just how hair biology works, and it's why we built Hair Code as a 3-month ritual rather than a 2-week fix.