Biotin, zinc, iron, cystine, brewer's yeast: these are the ingredients found in almost all hair supplements. The promise is always the same: stronger hair and less shedding. The honest answer is that they work well when there is a deficiency, and much less so when there isn't.
This guide explains what each ingredient does, what European law allows companies to claim, and when a supplement makes sense.
Article written by Elisa Avalle, founder of LeLang Skin Care and dermocosmetics specialist. Cover image generated with the support of artificial intelligence.
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Supplements, not cosmetics
You may hear them called “oral cosmetics” or “nutricosmetics.” Legally, they are not: a cosmetic is applied to the surface of the body, under Regulation (EC) No. 1223/2009. Hair capsules are food supplements, regulated by Directive 2002/46/EC and, in Italy, notified to the Ministry of Health.
The statements on the packaging also follow different rules: they may use only the health claims authorized by Regulation (EU) No. 432/2012, for nutrients present in sufficient quantities.
For hair, there are few authorized claims in Europe: biotin, zinc, and selenium “contribute to the maintenance of normal hair”; copper “contributes to normal hair pigmentation.” No authorized claim refers to reducing hair loss or promoting hair regrowth.
Why hair is affected by deficiencies
Hair follicle cells are among those that divide most rapidly throughout the body. They constantly need energy, proteins, vitamins, and minerals. When something is lacking, the body prioritizes vital organs, and hair suffers as a result: more hairs enter the resting phase and fall out several months later, while new hairs grow thinner and more fragile.
The ingredients, one by one
Biotin
It is a B vitamin needed for the metabolism of the follicle’s keratinocytes. True deficiency is rare and, when present, causes thinning and hair loss that improve after one or two months of supplementation. In people without a deficiency, there is no solid evidence that additional doses improve hair.
High doses of biotin can interfere with some blood tests, including thyroid tests and certain cardiac markers. If you take it, tell your doctor before having blood work done.
Zinc
It is a trace element involved in keratin synthesis. Zinc deficiency is associated with diffuse hair loss and fragile hair. Taking too much zinc for a long time, however, reduces copper absorption: here too, the dose matters.
Iron
It is the nutrient most studied in hair loss in women. Low iron stores, measured through ferritin, are associated with diffuse hair loss even without anemia. Iron should not be taken “just in case”: excess iron is harmful, and deficiency should always be confirmed with tests and monitored by a doctor.
Sulfur-containing amino acids: cystine and methionine
They are the building blocks of keratin, the protein hair is made of, which is rich in sulfur bridges. Methionine is essential and must be obtained through the diet. They are often found in supplements together with B vitamins.
Selenium and copper
Selenium has an authorized claim relating to the maintenance of normal hair, but excess selenium can itself cause hair loss. Copper is needed by the enzyme that produces melanin, which determines hair color: in gray hair, however, contributing to normal pigmentation does not mean restoring color, as we explain in the article on gray hair.
Brewer’s yeast, fatty acids, and antioxidants
Brewer’s yeast is a source of B vitamins and minerals. Omega-3 and omega-6 fatty acids improve hair softness and shine. Vitamin C, vitamin E, and other antioxidants protect cells from oxidative stress. They are reasonable ingredients, but the evidence for reducing hair loss is weaker.
When a supplement makes sense
- Confirmed deficiency based on blood tests: iron, zinc, vitamin D, vitamin B12, and folate.
- Temporary hair loss after a drastic diet, a period of inadequate nutrition, or severe stress, as support while the hair cycle returns to normal.
- Fragile, fine, and dull hair in people whose diet is unbalanced.
A supplement does not replace a varied diet, and it does not treat androgenetic alopecia, which should be managed by a dermatologist. If hair loss lasts more than two or three months, it is best to identify the cause before choosing a product. For the most common forms of hair loss, see the article on hair loss in autumn.
How to take them
- For at least three months: the hair cycle is slow, and results can only be seen in new hair growth.
- With meals, to improve tolerance.
- Without combining multiple supplements containing the same nutrients, to avoid exceeding the recommended doses.
- During pregnancy, breastfeeding, or ongoing treatment, only after discussing it with your doctor.
Frequently asked questions
Does biotin make hair grow?
It helps people who are deficient, which is rare. In people with normal levels, there is no evidence that it makes hair grow faster or thicker.
How long does it take to see results?
At least three months. Hair grows by an average of about one centimeter per month, and improvement can only be seen in hair that grows during supplementation.
Do hair supplements cause weight gain?
No. Vitamins and minerals do not provide significant calories at supplement doses.
Are they also useful for nails?
Nails and hair are made of the same protein, keratin, and are affected by the same deficiencies. The reasoning is the same: they are useful if something is lacking.
Sources for this article
Almohanna H.M. et al. “The role of vitamins and minerals in hair loss: a review,” Dermatology and Therapy, 2019. Patel D.P. et al. “A review of the use of biotin for hair loss,” Skin Appendage Disorders, 2017. Commission Regulation (EU) No. 432/2012, list of permitted health claims. Directive 2002/46/EC on food supplements. Regulation (EC) No. 1223/2009 on cosmetic products.
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