What you eat and hair loss
Nutrition matters for hair — but almost entirely in one direction: correcting a real deficiency helps, and supplementing without one does nothing. Here's how to tell which situation you're in.
Iron and ferritin: the classic contributor
Iron deficiency is the best-documented nutritional contributor to shedding, particularly in women. A dermatology review in JAAD discusses ferritin testing in the hair-loss workup while noting the evidence stops short of recommending universal screening — so it is a conversation to have, not a test to demand. Correcting a genuine deficiency helps; iron supplementation without one carries risk and no benefit.
Trost et al., iron deficiency and hair loss, JAAD 2006
Vitamin D, zinc, and the supplement aisle
A review in Dermatology and Therapy found deficiency states associated with several hair-loss types — and, consistently, that supplementing helps only those who are actually deficient. That single finding invalidates most of the marketing in this category.
Almohanna et al., vitamins and minerals in hair loss, Dermatology and Therapy 2019
Crash diets and rapid weight loss shed hair
Hair is protein, and aggressive caloric restriction is a recognized shedding trigger. This is directly relevant to anyone losing weight quickly on a GLP-1: the protein target that protects muscle also protects hair, and the appetite suppression that makes the medication work is exactly what makes under-eating protein easy.
Morton et al., protein intake meta-analysis, Br J Sports Med 2018
Biotin, the best-marketed non-answer
Deficiency is rare, evidence for supplementation in non-deficient people is essentially absent, and high doses interfere with laboratory tests including cardiac markers — the subject of an FDA safety communication.
FDA safety communication: biotin interference with lab tests
What to actually do
- Blood panel before supplement subscription — deficiency is the only situation where supplements reliably help.
- Losing weight fast? Hit protein targets; hair and muscle compete for the same shortfall.
- Pattern loss is hormonal: the proven generics cost $5–$15 a month, far less than most supplements.
- Sudden, patchy, or scarring loss belongs with a dermatologist, not a shopping list.
Educational content built on the cited literature — not medical or nutrition advice for your situation. Lifestyle change complements treatment; it is not a reason to stop or avoid medication your clinician prescribed. Decisions belong with you and a licensed clinician.