Vitamins for Skin, Hair and Nails — Which Ones Really Work?

The supplement market for “skin, hair and nails" is an industry worth billions every year. The packaging promises thick hair, radiant skin and strong nails — all you have to do is swallow the capsules. But what does the science actually say about each vitamin and mineral? Let's look at the evidence — honestly, and with a clear level of certainty for each.

Biotin (vitamin B7) — a marketing king, not a scientific one

Biotin is by far the most heavily marketed supplement for hair and nails. Manufacturers offer doses of 2.5–10 mg (2,500–10,000 µg), which is many times the daily requirement (30 µg).

The truth is that biotin only helps people who are actually deficient in it — and biotin deficiency is extremely rare in people who eat a balanced diet. In a review published in Skin Appendage Disorders, Patel and colleagues (2017) analysed 18 studies and concluded that there is insufficient evidence that biotin works in people without a documented deficiency.

When biotin can genuinely help (at a dose of 2.5 mg/day):

• Biotin deficiency confirmed by lab testing.
• Inherited biotinidase deficiency.
• Use of certain anti-epileptic drugs (carbamazepine, phenytoin).
• Long-term consumption of raw egg white (avidin binds biotin).

Level of evidence: LOW — for the general population there is no confirmed benefit.

An important note: high-dose biotin distorts laboratory test results (troponin, TSH, hCG). Tell your doctor about any supplementation before having blood tests.

Zinc — solid evidence, but in moderation

Zinc is involved in more than 300 enzymatic reactions, including the synthesis of keratin and collagen. The recommended daily allowance (RDA) is 8 mg for women and 11 mg for men.

The scientific evidence for zinc's role in skin and hair health is moderately strong:

• Acne: a meta-analysis (Yee et al., 2020) found lower zinc levels in patients with acne. Supplementation of 30 mg/day produces a moderate improvement.
• Hair loss: Karashima et al. (2012) showed a correlation between low zinc and telogen effluvium. Supplementation helps when a deficiency is confirmed.
• Wound healing: zinc is essential for cell proliferation and collagen synthesis — this is well documented.

Level of evidence: MODERATE — especially where a deficiency is confirmed.

Vitamin A (retinol) — powerful, but dangerous in excess

Vitamin A is crucial for the differentiation of epidermal cells and the function of the sebaceous glands. Retinoids (vitamin A derivatives) are some of the most effective dermatological drugs — isotretinoin revolutionised the treatment of severe acne.

However, taken orally in excess, vitamin A is hepatotoxic and teratogenic (it causes birth defects). Hypervitaminosis A can lead to:

• Liver damage.
• Headaches and nausea.
• Dry skin (paradoxically).
• Hair loss.

Do not supplement vitamin A without consulting a doctor. Beta-carotene (provitamin A from vegetables) is safer — the body converts it as needed.

Level of evidence: HIGH for prescription retinoids; LOW for supplementation in people without a deficiency.

Vitamin C — a cofactor in collagen synthesis

Vitamin C (ascorbic acid) is essential for collagen synthesis — it hydroxylates proline and lysine in the collagen chains. Without vitamin C, collagen is unstable — which is the cause of the symptoms of scurvy (bleeding, poor healing).

With a proper diet (fruit and vegetables), vitamin C deficiency is rare in developed countries. Supplementation above the RDA (75–90 mg/day) has not been shown to provide additional skin benefits in well-nourished people.

Vitamin C used topically (in creams and serums) has better evidence — it acts as an antioxidant, lightens pigmentation and supports photoprotection. Browse products containing vitamin C in our ingredient search.

Level of evidence: HIGH for its biological role; LOW for supplementation above the RDA in healthy people.

Vitamin E — an antioxidant with limited evidence

Vitamin E (tocopherol) protects cell membrane lipids from oxidative stress. In theory it should protect the skin against photoaging — and in vitro data are promising. However, clinical trials of oral supplementation have not shown clear dermatological benefits in people without a deficiency.

Like vitamin C, vitamin E may be more effective in topical form. High oral doses (>400 IU/day) may increase the risk of bleeding.

Level of evidence: LOW for oral supplementation for skin.

Iron — ferritin and hair loss

Iron deficiency is the most common nutritional deficiency in the world — and one of the most frequent causes of excessive hair loss in women of reproductive age. The key parameter is ferritin (the iron-storage protein).

A study by Trost et al. (2006) in the Journal of the American Academy of Dermatology showed that ferritin below 30 ng/ml is associated with telogen effluvium. Some dermatologists recommend keeping ferritin above 40–70 ng/ml for optimal hair growth.

However, supplementing iron without a confirmed deficiency is potentially dangerous — excess iron is toxic and pro-inflammatory. Always check your ferritin and full blood count before starting supplementation.

Level of evidence: MODERATE–HIGH in cases of deficiency; do NOT supplement iron without testing.

Summary — before you buy a supplement

1. Get tested — a full blood count, ferritin, zinc, vitamin D and B12 are the basics.
2. Eat a varied diet — most vitamins should come from food.
3. Don't believe the marketing — a “beauty complex" without a documented deficiency is money down the drain.
4. Consult a doctor before supplementing vitamin A and iron.

Want to know which vitamins your cosmetics contain? Check their ingredients on the PurScore ingredients page.