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Cysteine & L-Cystine

NUTRIENTS FOR HEALTHY HAIR
NUTRIENT
RECOMMENDED DOSAGE
FOUND IN THESE FOODS
CYSTEINE & L-CYSTINE (THE OXIDIZED FORM OF CYSTEINE) 32
(an amino acid)
100 mg/day 2

Table 50: Cysteine and L-cystine
WHAT IT DOES & EVIDENCE OF BENEFIT
Cysteine & L-cystine are important for healthy hair.
  • These two amino acids easily convert into each other; cysteine is a component of the main keratin protein in hair. 37

  • Deficiency or dysfunctional metabolism of L-cystine can cause hair loss, dry brittle hair, and premature grey hair. 32

  • Increases sulfur content in hair; animal studies show that supplementing with sulfur-containing amino acids such as L-cystine leads to increased hair growth. 2, 32

  • Cysteine is an antioxidant by itself, and is a precursor to glutathione, an important natural antioxidant that helps detoxify the body and protect against free radical damage which contributes to hair loss. 32, 37

  • In studies, L-cystine (usually with vitamin B complex) has been shown to reduce hair shedding and increase hair strength. This includes a controlled clinical trial involving women with telogen effluvium. 32

  • Taken with vitamin B complex (especially B6) improves hair growth rate. 32

  • People with diabetes should consult with their health care provider before taking cysteine supplements since they may interfere with insulin. 37
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Goitrogenic food that inhibits thyroid function; avoid raw; limit cooked servings to no more than 3 per week.
Also has antioxidant properties.