Key takeaways
- Genetics dominates hair volume — no supplement rewrites that.
- Iron, protein and vitamin D deficiencies cause real hair loss.
- Biotin only helps if you're actually deficient — which is rare.
- Chronic stress causes telogen effluvium — often reversible.
Set expectations before spending money
The uncomfortable truth: much of hair volume is set by genetics. No product turns fine hair thick, and no supplement grows back hair that androgen sensitivity has retired.
That said, plenty of hair problems are not about genetics — they're about nutrition, stress, styling damage, or scalp health. Those are the ones worth addressing.
What actually causes hair problems in otherwise healthy people
- Iron deficiency — extremely common in menstruating women. Check ferritin, not just haemoglobin
- Vitamin D deficiency — common in indoor lifestyles
- Not enough protein — hair is 95% keratin, a protein. Underfed hair thins
- Chronic stress — pushes hair into shedding phase 2–3 months later. Real, common, usually reversible
- Post-illness or postpartum shedding — normal, temporary, self-limiting
- Scalp conditions — dandruff, seborrheic dermatitis. Treatable
What the internet gets wrong
Biotin gummies. They dominate hair supplement marketing. Biotin only helps if you're actually deficient — and true biotin deficiency is genuinely rare unless you have specific medical conditions. Excess biotin can also interfere with certain lab tests. Stop.
Rice water. Onion juice. Rosemary oil. There's more marketing than evidence. Rosemary oil has one small trial suggesting it may compare to minoxidil in a specific pattern of loss. Onion juice mostly makes you smell like onions.
If a hair product's marketing shouts louder than its ingredient list, treat that as information.
— Dr. Elena Marín
What has actual evidence
- Minoxidil (topical or oral) — for pattern hair loss, evidence-based, prescription usually needed
- Finasteride/Dutasteride — for men, prescription
- PRP injections — modest evidence, expensive
- Adequate iron, protein, vitamin D — if you're deficient, correcting it matters
- Sleep, stress management — hair reflects overall health surprisingly well
If you're worried about hair loss, see a dermatologist — not the internet. Early treatment matters.
The takeaway
Hair health starts with basic nutrition, sleep, and stress management. Skip most supplements. Skip most viral serums. If you have a genuine problem, see a dermatologist — real treatments exist, and starting them early matters.
See also our grey hair guide for the pigment side of the story.
