Vitamin B3 (nicotinamide) — the DNA-repair protocol for skin cancer prevention

For people with a history of skin cancer, nicotinamide — the amide form of vitamin B3, also called niacinamide — is a foundational, low-cost part of a medical prevention plan. It is one of the few supplements with a genuine randomised evidence base for reducing new non-melanoma skin cancers, and the case for it has only strengthened with newer real-world data. ^(1,2)

The evidence: ONTRAC, and a major 2025 update

The landmark evidence is the ONTRAC randomised controlled trial, published in the New England Journal of Medicine in 2015. In 386 patients who had had at least two non-melanoma skin cancers in the previous five years, 500 mg of nicotinamide twice daily for 12 months reduced new non-melanoma skin cancers by 23% compared with placebo (95% CI 4–38%; P = 0.02), with similar reductions in new basal cell and squamous cell carcinomas and fewer actinic keratoses. ⁽¹⁾

The 2025 cohort: bigger effect when you start early

In September 2025, JAMA Dermatology published a much larger real-world study that has made me even more confident recommending vitamin B3. Using national health-record data, researchers compared 33,822 patients — about 12,000 taking nicotinamide 500 mg twice daily against roughly 21,000 matched patients who were not. ⁽²⁾

• Overall, nicotinamide was associated with a 14% reduction in subsequent skin cancer.
• Crucially, when nicotinamide was started after a person’s first skin cancer, the risk reduction rose to about 54% — a large effect — and the benefit was progressively smaller when started only after several skin cancers had already occurred.
• The greatest reduction was seen for squamous cell carcinoma. ⁽²⁾

The practical message is start early: the evidence now suggests the biggest payoff comes from beginning nicotinamide soon after a first non-melanoma skin cancer, rather than waiting until several have accumulated. (This 2025 study was a large observational cohort rather than a randomised trial, so it complements — not replaces — the randomised ONTRAC result; together they point the same way.) ^(1,2)

How nicotinamide protects the skin

It helps to picture skin cells as having a limited energy budget for repairs. UV radiation both damages DNA and depletes the cellular energy (ATP) needed to fix it. Nicotinamide is a precursor of NAD⁺, a molecule central to cellular energy metabolism, and by replenishing it nicotinamide is thought to:

• support DNA repair — helping cells correct UV-induced errors before they replicate
• reduce UV-induced immune suppression — helping the skin’s immune surveillance keep clearing abnormal cells ⁽¹⁾

The protocol: dose and form

• Dose: 500 mg of nicotinamide, taken orally twice daily (morning and night) — the regimen used in ONTRAC and in the 2025 cohort. ^(1,2)
• Form: ensure the product is nicotinamide or niacinamide. Do not use niacin (nicotinic acid), which causes flushing, headache and blood-pressure changes and was not the form studied.
• Consistency: the protective effect only lasts while you take it — in ONTRAC the benefit was not maintained after stopping, so it is a long-term measure. ⁽¹⁾

Which brand, and how many tablets?

The brand is not important — but in practice almost every patient asks me for a recommendation, so here is a straightforward one. In Australia, Blackmores Insolar® is very commonly stocked and is perfectly fine: it is a 500 mg nicotinamide tablet. Any equivalent 500 mg nicotinamide (niacinamide) product works just as well — ask your pharmacist for one.

One practical point that trips a lot of people up: the packaging on many of these supplements recommends only one tablet a day. The research, however, supports 500 mg twice daily — that is one 500 mg tablet in the morning and one at night — for skin cancer prevention. ^(1,2) If you are taking it for this reason, follow the twice-daily dose rather than the once-daily suggestion on the label.

Safety and statin considerations

Most people taking the correct form have no side effects. Because vitamin B3 is processed by the liver, a few precautions apply:

• Statins: for patients on cholesterol-lowering statins, we may monitor liver function and CK (creatine kinase) so the combination is tolerated.
• Liver disease: patients with significant liver disease should check with their doctor first.
• Tolerance: mild nausea or stomach discomfort is uncommon at this dose. Always confirm you are taking nicotinamide/niacinamide, not niacin.

The recent Australian “vitamin B toxicity” warnings relate to vitamin B6 (pyridoxine), a different vitamin — not the nicotinamide discussed here.

Topical vitamin B3 serums

Beyond the oral tablet, there is reasonable evidence that vitamin B3 applied to the skin helps too. Topical nicotinamide has photoprotective effects — it supports repair of UV-induced DNA damage and helps prevent UV-induced immune suppression in the skin — and trials have found it can reduce the number of actinic keratoses over time. ⁽⁴⁾ It is not a sunscreen and should never replace one, but it is a well-tolerated extra layer.

In practice I suggest a niacinamide (vitamin B3) serum at around 10% for daily use. As with the tablet, the brand is not too important — there are many good options. My personal preference, based on the general strength of their products, is La Roche-Posay.

Apply a few drops to the face and other sun-exposed areas such as the backs of the hands, once or twice daily after cleansing and before moisturiser or sunscreen. It is lightweight and rarely irritating, and over months of regular use it helps repair the skin barrier and support sun-exposed skin. ⁽⁴⁾

Dietary vitamin B3

Vitamin B3 also occurs naturally in many foods — lean meats and poultry, fish such as tuna and salmon, nuts, seeds and legumes, and wholegrain or fortified cereals and breads. ⁽⁵⁾ A balanced diet supports your skin’s general repair capacity, but diet alone cannot reach the ~1,000 mg per day used for prevention (the 500 mg twice-daily dose) — that level requires a supplement. Think of dietary B3 as background nutrition, not as the prevention strategy itself. ⁽⁵⁾

Where it fits

Nicotinamide is one layer in a broader prevention plan. It works best alongside:

• daily UV protection and behaviour change — see how to reduce your skin cancer risk →
• field therapy for established sun damage
• regular skin checks

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