Nicotinamide, an inexpensive form of vitamin B3, reduced the rate of new nonmelanoma skin cancers by roughly 23% over 12 months in a landmark clinical trial of high-risk patients who took 500 mg twice daily. That finding, published in the New England Journal of Medicine in 2015, remains the strongest evidence that a simple supplement can meaningfully lower the odds of the most common cancers in the world. But the story is more layered than “take a pill, prevent cancer,” and the details matter for anyone considering nicotinamide as part of their skin-protection strategy.
How Nicotinamide Shields Skin from UV Damage
Nicotinamide works through several overlapping pathways, all of which converge on one goal: helping skin cells recover from ultraviolet radiation before the damage snowballs into cancer. It is a precursor to a molecule called NAD+, which cells burn through rapidly when they are hit by UV light. Without enough NAD+, cells lose the energy they need to fix broken DNA and mount an immune response. Nicotinamide tops off that fuel supply.
In lab studies on human skin cells, nicotinamide prevented the drop in cellular energy that UV radiation normally triggers, and it enhanced the repair of two key types of DNA damage caused by UV exposure.1PubMed. Nicotinamide for photoprotection and skin cancer chemoprevention: A review of efficacy and safety That repair boost extends to melanocytes, the pigment-producing cells where melanoma originates. Nicotinamide increased the repair of oxidative DNA damage and UV-induced lesions in primary human melanocytes, confirmed through measurements of active DNA repair synthesis.2PubMed. Nicotinamide enhances repair of ultraviolet radiation-induced DNA damage in primary melanocytes
The immune angle is equally important. UV radiation suppresses the skin’s local immune surveillance, which is one reason chronic sun exposure leads to cancer: the immune system becomes less able to find and destroy abnormal cells. In human volunteers, oral nicotinamide at either 500 mg or 1,500 mg per day significantly reduced that UV-driven immune suppression, with no immune effects in skin that had not been irradiated.3PubMed. Oral nicotinamide protects against ultraviolet radiation-induced immunosuppression in humans When applied topically, nicotinamide also protected against immunosuppression from both UVB and UVA wavelengths.4PubMed. Topical nicotinamide modulates cellular energy metabolism and provides broad-spectrum protection against ultraviolet radiation-induced immunosuppression in humans In other words, nicotinamide helps skin cells fix damage before it becomes permanent and keeps the immune system alert enough to catch anything that slips through.
The Phase 3 Trial Behind the 500 mg Dose
The evidence that put nicotinamide on dermatologists’ radar came from the ONTRAC trial, a phase 3 randomized, placebo-controlled study conducted in Australia. It enrolled 386 people who had been diagnosed with at least two nonmelanoma skin cancers in the previous five years, making them a genuinely high-risk group. Participants took either 500 mg of nicotinamide twice daily (for a total of 1,000 mg per day) or a placebo for 12 months.
At the 12-month mark, the nicotinamide group had a 23% lower rate of new nonmelanoma skin cancers compared with placebo. Looking at subtypes, squamous cell carcinomas dropped by about 30% and basal cell carcinomas by about 20%, though the basal cell result did not reach traditional levels of statistical certainty. Actinic keratoses, the rough precancerous spots that often precede squamous cell carcinoma, were also reduced. They were about 11% fewer at three months, rising to a 20% reduction at nine months, settling at 13% lower by 12 months.5PubMed. A Phase 3 Randomized Trial of Nicotinamide for Skin-Cancer Chemoprevention
This trial stands out because it was large, well-designed, and tested a practical intervention. The supplement was cheap and over-the-counter. It asked a lot less of patients than other preventive strategies like field treatment with topical chemotherapy. And it is still the only phase 3 trial to demonstrate this effect in immunocompetent individuals.
Real-World Confirmation and Cost Savings
Clinical trials run under controlled conditions, so it is always worth asking whether benefits hold up when people take supplements on their own schedules, forget doses, and live in the messy real world. A large observational study using US Veterans Affairs data examined over 33,000 individuals and found that nicotinamide users had a lower rate of keratinocyte carcinomas (the umbrella term covering both basal cell and squamous cell cancers). The incidence was roughly 0.20 per person-year among nicotinamide users, compared with 0.26 per person-year in non-users.6JAMA Dermatology. Cost-Effectiveness of Oral Nicotinamide for Keratinocyte Carcinoma Prevention
A separate analysis of real-world data found that the lower skin cancer risk associated with nicotinamide use became statistically significant with as little as 30 days of exposure, and persisted across different durations of use.7JAMA Dermatology. Nicotinamide for Skin Cancer Chemoprevention That early signal is encouraging, though it does not mean 30 days of use gives you lasting protection (as we will see, the benefit disappears after discontinuation).
The cost-effectiveness numbers from the VA cohort are striking. Among roughly 12,000 nicotinamide users, an estimated 624 keratinocyte carcinomas were prevented annually. The total cost of supplying nicotinamide was about $161,000, while the treatment costs avoided came to over $526,000, resulting in net savings of about $365,000 per year for the cohort. That translated to a roughly 20% reduction in annual keratinocyte carcinoma treatment costs.6JAMA Dermatology. Cost-Effectiveness of Oral Nicotinamide for Keratinocyte Carcinoma Prevention For a supplement that typically costs between $10 and $20 per month out of pocket, the math is hard to argue with for high-risk patients.
Protection Fades After You Stop
One of the most underappreciated findings from the ONTRAC trial is that the protective effect vanished after nicotinamide was discontinued. The original report stated there was no evidence of benefit after nicotinamide was stopped.8New England Journal of Medicine. A Phase 3 Randomized Trial of Nicotinamide for Skin-Cancer Chemoprevention This makes biological sense: nicotinamide is not killing pre-cancerous cells or permanently altering the skin. It is boosting cellular energy and repair capacity, which drops back to baseline once the supplement is withdrawn.
For patients, this means nicotinamide is a maintenance strategy, not a course of treatment. You take it continuously to maintain the benefit. Your dermatologist might recommend staying on it indefinitely if your risk profile warrants it, similar to how daily sunscreen is a lifelong commitment rather than a one-time fix. Skipping it for a month while on vacation from the pharmacy could be the worst time to stop, since sun exposure during that gap would go unassisted by the extra repair capacity nicotinamide provides.
One Important Group Where It Did Not Work
The excitement around the ONTRAC trial naturally raised hopes for organ transplant recipients, who face massively elevated skin cancer rates because of the immunosuppressive drugs they take to prevent rejection. A dedicated trial tested nicotinamide in exactly this population. The results were definitively negative: at 12 months, there were 207 new keratinocyte cancers in the nicotinamide group and 210 in the placebo group, a rate ratio of 1.0 with a confidence interval spanning 0.8 to 1.3. No differences appeared for squamous cell carcinomas, basal cell carcinomas, or actinic keratoses.9PubMed. Nicotinamide for Skin-Cancer Chemoprevention in Transplant Recipients
The most likely explanation is that nicotinamide’s benefit depends heavily on a functioning immune system. Part of its protective mechanism is restoring UV-suppressed immune surveillance. In transplant recipients, that immune surveillance is deliberately and profoundly blunted by their medications. Nicotinamide can still enhance DNA repair, but without the immune system doing its part, that is not enough to shift cancer rates. This finding is a genuinely important negative result. If you are a transplant recipient hoping to reduce skin cancer risk, nicotinamide is not the answer, and your dermatologist will need to discuss other approaches.
Who Should Consider It
A systematic review and meta-analysis of the available evidence concluded that oral nicotinamide is recommended for individuals with a “field of cancerization” (widespread sun damage across a body area) or with at least one prior cutaneous squamous cell carcinoma.10PubMed Central. Effect of Nicotinamide in Skin Cancer and Actinic Keratoses Chemoprophylaxis, and Adverse Effects Related to Nicotinamide: A Systematic Review and Meta-Analysis This is where dermatology guidelines have landed: nicotinamide is not being suggested for everyone who spends time outdoors, but for people with a demonstrated track record of developing skin cancers or their precursors.
The typical regimen mirrors the ONTRAC protocol: 500 mg twice daily. Some earlier immunosuppression studies used 500 mg once daily and still showed benefit for UV immune protection, so there is a plausible case for a lower dose, but the cancer-prevention data specifically comes from the 1,000 mg/day total dose.3PubMed. Oral nicotinamide protects against ultraviolet radiation-induced immunosuppression in humans If you have had multiple nonmelanoma skin cancers, frequent actinic keratoses, or extensive photodamage, this is worth discussing with your dermatologist. If your skin cancer history is limited to one basal cell carcinoma years ago, the benefit-to-hassle ratio is less clear, and sun protection alone may suffice.
Safety and Tolerability
Nicotinamide has a reassuring safety record at the doses used for cancer prevention. The ONTRAC trial found no meaningful difference in adverse events between the nicotinamide and placebo groups over 12 months. A broader review of safety data found that long-term oral intake of up to 1 g per day is well tolerated, and studies testing much higher doses (up to 12 g per day for as long as a year) reported a relative lack of toxicity, giving nicotinamide an extremely high therapeutic index.11JAAD Reviews. Examining the safety of nicotinamide for skin cancer prevention: Review of adverse events, metabolism, and toxic dosages
Occasional mild gastrointestinal discomfort has been reported at higher doses, but at 500 mg twice daily this is uncommon. The supplement does not interact with most common medications in a clinically significant way, though as with any new supplement, mentioning it to your prescribing physician is sensible. Liver toxicity, sometimes flagged for high-dose niacin, has not been a concern at these nicotinamide doses. The low side-effect profile is one of the main reasons dermatologists are comfortable recommending it broadly to high-risk patients.
Could Nicotinamide Help Prevent Melanoma?
The ONTRAC trial focused on nonmelanoma skin cancers. Melanoma is a different and deadlier disease, and no randomized trial has yet tested whether nicotinamide reduces melanoma incidence. The biological rationale, though, is real. Nicotinamide enhances DNA repair in melanocytes specifically, reduces UV-induced immunosuppression, and modifies the inflammatory environment that UV creates in the skin. Based on these mechanisms, researchers have described nicotinamide as a promising agent for melanoma chemoprevention in high-risk populations.12Wiley Online Library. Melanoma and nonmelanoma skin cancer chemoprevention: A role for nicotinamide?
“Promising” is doing a lot of work in that sentence, however. The gap between enhancing melanocyte DNA repair in a laboratory and actually preventing melanoma in living humans is enormous. Melanoma has a more complex relationship with UV exposure than squamous or basal cell carcinoma, involving intermittent intense burns as well as cumulative exposure, and different genetic drivers. Until a clinical trial addresses this directly, nicotinamide cannot be recommended specifically for melanoma prevention. But for patients already at high risk for both melanoma and nonmelanoma skin cancers (a common overlap in fair-skinned, sun-damaged individuals), the nonmelanoma benefit alone may justify its use while additional research catches up.
Why Dietary Intake Falls Short
Nicotinamide is a form of niacin (vitamin B3), and niacin is present in foods like poultry, fish, legumes, and fortified cereals. Could you eat your way to a skin-cancer-protective dose? Not realistically. The recommended daily allowance for niacin is 14 to 16 mg per day for adults, and an analysis of two large US cohorts found that over 80% of participants consumed above the RDA, partly because multivitamin use is so common. But even the highest dietary intake levels fell far below the 1,000 mg per day used in cancer prevention trials.13PubMed Central. Niacin intake and risk of skin cancer in US women and men
The gap is not small. You would need to eat roughly dozens of chicken breasts per day to approach 1,000 mg of niacin equivalents from food alone. Supplementation is the only practical route to the pharmacological doses that trials have shown to be effective. And the supplement in question is specifically nicotinamide (also labeled niacinamide), not niacin in its other common form, nicotinic acid.
Nicotinamide Is Not Niacin, and Other Supplement Pitfalls
This distinction trips up a surprising number of people. Both nicotinamide and nicotinic acid are forms of vitamin B3, and both can be converted to NAD+ in the body. But nicotinic acid (commonly sold as “niacin”) causes flushing: a red, hot, sometimes itchy skin reaction that can be deeply unpleasant. Nicotinamide does not cause flushing. All of the skin cancer prevention research has used nicotinamide, not nicotinic acid. If you pick up a bottle labeled “niacin” or “flush-free niacin” (which is sometimes a different compound called inositol hexanicotinate), you may not be getting what was tested.
Newer NAD+ precursors like nicotinamide riboside and nicotinamide mononucleotide (NMN) have generated buzz in the longevity community, but there are no clinical trials testing their ability to prevent skin cancer. They are substantially more expensive and have not been shown to be superior to plain nicotinamide for this purpose. Stick with what has been tested.
Supplement quality is also worth a mention. Testing of NMN and other geroprotective supplements found significant deviations from labeled amounts, ranging from 29% above to 100% below the stated dose.14PubMed Central. Testing the amount of nicotinamide mononucleotide and urolithin A as compared to the label claim That particular analysis focused on NMN and urolithin A rather than nicotinamide specifically, but it underscores a broader problem in the supplement market: what is on the label is not always what is in the capsule. Choosing a product from a manufacturer that submits to third-party testing (look for USP, NSF, or ConsumerLab seals) provides some reassurance that you are actually getting 500 mg per tablet.
Genetic Conditions with Extreme UV Sensitivity
Xeroderma pigmentosum is a rare genetic disorder in which the body’s ability to repair UV-induced DNA damage is severely impaired. People with the condition develop skin cancers at dramatically young ages, sometimes in childhood. Because nicotinamide enhances DNA repair, there has been theoretical interest in using it for these patients. Reviews of investigational therapies for xeroderma pigmentosum have listed nicotinamide as a potential approach that could help compensate for the faulty repair system.15PubMed Central. Current Therapeutic Strategies of Xeroderma Pigmentosum
The reality is more sobering. No clinical studies of oral nicotinamide have been conducted in xeroderma pigmentosum patients, largely because the disease is so rare that recruiting enough participants for a trial is extraordinarily difficult.16PubMed Central. Xeroderma pigmentosum: an updated review Some dermatologists may still prescribe it off-label for these patients, reasoning that the safety profile is excellent and the biological mechanism is sound even without trial proof. But families dealing with xeroderma pigmentosum should understand that this use remains experimental and should be managed by a specialist familiar with the condition, rather than treated as a reliable prevention tool.
Nicotinamide as Part of a Broader Strategy
Even the best-case reading of the evidence positions nicotinamide as one layer of protection, not a replacement for the basics. Sunscreen, protective clothing, and avoiding peak UV hours remain the foundation. The ONTRAC trial enrolled participants who were already receiving standard dermatologic care, including regular skin checks. Nicotinamide provided its roughly 23% reduction on top of that baseline vigilance, not instead of it.
Some dermatologists describe the approach as “belt and suspenders.” Sunscreen blocks a portion of UV before it reaches the skin. Nicotinamide helps the skin deal with the UV that gets through. Regular skin exams catch anything that develops despite both measures. Each layer reduces risk incrementally, and for someone who has already demonstrated a pattern of developing skin cancers, stacking these layers is the rational approach. A supplement costing a few cents per day, with minimal side effects and real evidence behind it, fits into that framework about as cleanly as any intervention in medicine.