Supplements and Skin Cancer Risk: What May Help, What to Avoid

No supplement has been shown to prevent melanoma. One, nicotinamide (vitamin B3), lowered the number of new non-melanoma skin cancers in a trial of people who had already had several. Vitamin D, beta-carotene and selenium were all tested in large trials and did not lower skin cancer overall, and two of them came with warning signs.

So the evidence supports a narrow, doctor-guided use of one supplement, caution with several others, and sunscreen, shade and skin checks for everyone.

In the ONTRAC trial (The New England Journal of Medicine, 2015), 386 adults who had had at least two non-melanoma skin cancers took nicotinamide 500 mg twice daily or a placebo for 12 months. The nicotinamide group had about 23% fewer new non-melanoma skin cancers. The effect faded after they stopped.

A 2023 trial in organ transplant recipients (ONTRANS) found no benefit, and a large 2025 study of US veterans in JAMA Dermatology found a lower risk mainly when nicotinamide was started after a first skin cancer. That study was observational, so it shows an association, not proof. This is a supplement to discuss with a dermatologist if you have had skin cancer, not a general prevention pill.

Vitamin D matters for bones and general health, and supplements are a safer way to get it than deliberate sun exposure or tanning beds. But trials have not shown that vitamin D supplements lower skin cancer risk overall. In the Women's Health Initiative trial of calcium plus vitamin D (results reported in the Journal of Clinical Oncology in 2011), supplements did not reduce non-melanoma skin cancer or melanoma overall. The large VITAL trial (The New England Journal of Medicine, 2019) found no reduction in total cancer incidence with vitamin D.

If you are low in vitamin D, a supplement your doctor recommends is reasonable. It does not replace sun protection.

Two large trials found harm. In the ATBC study of Finnish male smokers (The New England Journal of Medicine, 1994), 20 mg of beta-carotene a day was linked to more lung cancers. The CARET trial (The New England Journal of Medicine, 1996), which combined beta-carotene with vitamin A in smokers and asbestos-exposed workers, was stopped early because lung cancer and deaths were higher in the supplement group.

For skin, the Physicians' Health Study found that 12 years of beta-carotene supplements did not change the risk of non-melanoma skin cancer. Carotenoids from food are fine; high-dose beta-carotene supplements are best avoided by smokers and recent ex-smokers.

Selenium was tested in the Nutritional Prevention of Cancer trial (JAMA, 1996) in people who had already had basal or squamous cell skin cancer. Taking 200 micrograms a day did not reduce new skin cancers, and later follow-up (Journal of the National Cancer Institute, 2003) found a slightly higher risk of squamous cell carcinoma in the selenium group. There is no case for selenium as skin cancer prevention.

Some supplements can make skin more sensitive to light. St John's wort contains hypericin, which can cause photosensitivity, and it interacts with many prescription medicines, including immunosuppressants used after transplants. Some herbal products contain psoralen-type compounds (furocoumarins) that also increase light sensitivity. If you take any of these, extra sun protection matters, and your pharmacist or doctor should know.

Talk to your doctor or dermatologist first, particularly if you have had skin cancer, have had an organ transplant or take immunosuppressants, are pregnant or breastfeeding, have kidney or liver disease, or take regular medicines. Bring the actual bottle or label so they can check the form and dose.

Be wary of any product that claims to prevent, treat or cure skin cancer or to replace sunscreen. US law does not allow supplements to make disease claims, and the FDA has warned sellers that did.

Broad-spectrum SPF 30+ sunscreen used every day, shade around midday, hats, sunglasses and covering clothing, and no tanning beds. These have far stronger evidence than any supplement.

The other half of prevention is catching problems early. Know your skin, check it monthly, and get any spot that is new, changing, bleeding or not healing looked at by a doctor.