Vitamin B3 Nicotinamide and Cancer

Vitamin B3 is also called niacin, nicotinic acid and nicotinamide. Niacin derives from "nicotinic acid vitamin." Vitamin B3 occurs in the body as nicotinamide, a water-soluble isotype of vitamin B3. It occurs naturally in meat, dairy products, legumes, kernels, seeds, leafy vegetables, yeast, coffee and tea. It is widely used as a cream ingredient in dermatology and attracts interest as a new agent against nonmelanoma skin cancer.

What is vitamin B3?

Vitamin B3 (nicotinic acid) is a derivative of pyridine. Although chemically related to nicotine, its physiological effects are not similar. It is a water-soluble white crystalline powder, resistant to heat and light, perhaps the most stable vitamin. It is easy to synthesize.

Vitamin B3's function: Nicotinamide enables respiratory enzymes required for cells to use oxygen to function. It is converted into coenzymes needed for DNA repair mechanisms.

Vitamin B3 deficiency may cause diseases of the skin and gastrointestinal tract. The best known is pellagra (rough skin). Today, it occurs only in some poor populations with monotonous diets. The exact mechanisms of deficiency-related problems have not been fully clarified.

Vitamin B3 and nonmelanoma skin cancers

Some human studies evaluated oral vitamin B3's effects on a benign but potentially cancerous skin lesion called actinic keratosis and on nonmelanoma skin cancers.

Actinic keratosisconsists of lesions reflecting abnormal skin cell growth in sun-exposed areas due to prolonged uncontrolled exposure to sunlight and ultraviolet (UV) rays. They usually have rough surfaces, sometimes scaly patches. There is a low risk of progression to skin cancer.

In a phase-2 clinical study, people with at least 4 actinic keratoses, numbering 88, received 1 or 2 daily doses of 500 mg vitamin B3 or placebo. After 4 months, actinic keratosis numbers fell by up to 35% compared with placebo.

Skin cancers are classified as melanoma and nonmelanoma skin cancers, making 2 categories. Melanomas account for less than 5% of all skin cancers but behave aggressively (rapid growth and spread). Nonmelanoma cancers have two main types: basal cell carcinoma and squamous cell carcinoma.

A larger phase 3 clinical study showed that nicotinamide reduced new actinic keratoses and nonmelanoma skin cancers. In this trial with 5 years of follow-up, patients with at least 2 nonmelanoma skin cancers, numbering 386, received twice-daily 500 mg nicotinamide or placebo for 1 year. Compared with placebo, nicotinamide reduced the risk of new nonmelanoma skin cancers over 1 year by 23% (20% for basal cell carcinomas and 30% for squamous cell carcinomas).

Conclusion

Clinical findings suggest oral nicotinamide may reduce numbers and development rates of actinic keratoses and new nonmelanoma skin cancers in high-risk patients. Vitamin B3 can therefore be considered, specifically for nonmelanoma cancers, a chemopreventive agent. Although generally well tolerated, nicotinamide at high doses may cause nausea and vomiting. This study should not be used to support general vitamin use, and vitamins for cancer treatment or prevention should not be encouraged without medical advice.

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