What hair is made of — keratin, sulfur amino acids and the nutrients behind them

The hair you see is dead cells packed with protein. The living part is the follicle under the scalp, dividing rapidly to push out about 1 cm of new hair a month [1]. Knowing what hair is built from explains why diet matters.

Keratin: the main protein

Dry hair is mostly protein — hard keratin — with the rest water, lipids, pigment and trace minerals [2]. Keratin forms long coiled filaments bundled into the cortex, the core that sets strength and elasticity, protected by the overlapping scales of the cuticle [3].

Sulfur: what makes hair strong

Hair keratin is unusually rich in the amino acid cysteine, which contains sulfur. Neighbouring cysteines link into disulfide bonds — the rivets that lock keratin filaments together and let hair resist pulling, heat and water [2][3]. Perming and straightening work by breaking and re-forming these bonds, which is why chemically treated hair turns brittle.

The body gets cysteine from dietary protein and can also make it from methionine, an essential amino acid that must come from food. Together they are the sulfur amino acids.

The nutrients behind the hair factory

The follicle is one of the fastest-dividing tissues in the body, so it needs a steady supply of raw material and cofactors [1][4].

• Protein and sulfur amino acids — the direct raw material of keratin; low intake is linked to thinner hair and more shedding [4][5]
• Zinc — needed for cell division and protein synthesis; deficiency is a clinical cause of hair loss [4]
• Iron — carries oxygen to the follicle; low ferritin is common in diffuse shedding [4][5]
• Biotin and other B vitamins — coenzymes in energy and protein metabolism, clearly important when deficient [4]
• Vitamin C — aids iron absorption from plants and acts as an antioxidant [4]
• Selenium and copper — in antioxidant enzymes and pigment formation; both deficiency and excess are harmful [4]

What this means in practice

Hair is a non-essential tissue, so when the body is short of something the follicle is among the first to be rationed. That is why hair reflects nutrition and health from two to four months earlier [5]. A varied diet with enough protein is the foundation; supplements have a role for people who do not get enough each day, and unusual shedding should always be checked by a doctor first.

U-TURN combines L-cysteine, L-methionine, zinc, iron, biotin, selenium and other nutrients — 18 in one capsule. Biotin, zinc and selenium contribute to the maintenance of normal hair, for people who do not get enough from food each day · Dietary supplement; not intended to prevent or treat any disease.