Nicotinamide

Nicotinamide, a form of vitamin B3, has one randomised trial showing fewer skin cancers in people who had already had them. The effect was modest, and a trial in organ-transplant recipients found nothing.

If you have had non-melanoma skin cancer, ask your dermatologist about 500 mg of nicotinamide twice a day, taken every day as a preventive. If you haven't, there is no evidence it protects you, and it never replaces sunscreen or avoiding sunburn.

What it is

Nicotinamide is a form of vitamin B3.^[1] The proposed reason it could prevent skin cancer is that it supports the energy-hungry machinery cells use to repair DNA damaged by ultraviolet (UV) light. That is a mechanism, not proof; what matters is the trials.

The trial that made its name

In a randomised trial of 386 people who had already had at least two non-melanoma skin cancers (the common basal-cell and squamous-cell types), 500 mg of nicotinamide twice a day cut new non-melanoma skin cancers by 23% over a year compared with placebo. The true effect could plausibly be anywhere from a 4% to a 38% reduction.^[2]

That is a real but modest effect, in a high-risk group. It says nothing about healthy adults who have never had skin cancer, and it should not be stretched to them.

Where it didn't work

Organ-transplant recipients take drugs that suppress the immune system, and they develop squamous-cell skin cancer at more than 65 times the usual rate^[3], so they had the most to gain. A placebo-controlled trial in this group found no benefit: 207 new skin cancers on nicotinamide against 210 on placebo. The trial was small and was stopped early because it struggled to recruit, so it cannot rule out a small effect. It found no sign of one, though.^[4]

Real-world data

A large retrospective study of US veterans found about 14% fewer new skin cancers overall in people taking nicotinamide. When they started after their first skin cancer, the figure was about 54% fewer.^[5] The veterans were mostly older men, and a look back at records cannot rule out that people who chose to take it differed in other ways. It supports the trial's direction but is weaker evidence.

Safety and limits

For the other common form of B3, plain niacin (nicotinic acid), the European upper limit for supplements is low, 10 mg a day, because of its flushing. For nicotinamide, the European Food Safety Authority (EFSA) overview lists a much higher limit, 900 mg a day.^[6] The trial dose, 500 mg twice a day (1,000 mg in all), is slightly above that limit.

A 2024 study linked two breakdown products of B3 and NAD+ (nicotinamide adenine dinucleotide), called 2PY and 4PY, to a higher three-year risk of major cardiovascular events; that is an association backed by mouse work, not proof of harm.^[7] A 2025 health-records study of 13,108 patients (91% men, average age 67), about 5,300 of whom took nicotinamide, found no overall increase in major cardiovascular events (heart attack, stroke or cardiovascular death), though some estimates were imprecise.^[8]

What it is not

Not a "high-exposure day" pill. Every study tested continuous daily use in people with past skin cancer. Nothing supports taking it before a beach day.
Not a sunscreen substitute. The same goes for the other oral "photoprotectants", Polypodium leucotomos extract and astaxanthin. They rest on small, short trials, including industry-funded ones; see Sun exposure.

What to do

If you have had basal-cell or squamous-cell skin cancer, raise nicotinamide (500 mg twice a day, every day) with your dermatologist as a modest add-on.
If you are a transplant recipient, the one trial in your group found no benefit; rely on sun protection and regular skin checks.
If you have never had skin cancer, there is no evidence it helps you.
Whatever your history: sunscreen for long stretches outdoors, never burn, and, if you've had skin cancer, a yearly dermatology check.