The relationship between nutrition and hair health is one of the areas where marketing claims and scientific evidence get most tangled.
Evidence-Based Links
A systematic review published in 2025 found that deficiencies in zinc, copper, magnesium, selenium, vitamins B12, E, and D, and folic acid were all associated with androgenetic alopecia progression. Iron deficiency is the most well-documented nutrient link to hair loss — particularly worth evaluating in menstruating women.
Biotin: An Overhyped Supplement
Biotin is the most heavily marketed hair supplement ingredient, yet it sits at the lowest tier of evidence for treating hair loss in people without a confirmed deficiency.
Excess Can Also Harm
Excess zinc supplementation can impair copper absorption and paradoxically cause hair loss; too much vitamin A or selenium can also increase shedding. "More is better" doesn't apply here.
A Practical Approach
Most people can meet all their nutritional needs through a balanced diet. Before starting supplements, a real deficiency should be confirmed via blood work and corrected under medical supervision.