Skin Cancer and Diet

It may come as no surprise that what we eat directly affects our chances of getting skin cancer. In our first story, we look at the best supplement for preventing skin cancer. 

Nicotinamide, also known as niacinamide, is a form of vitamin B3 that has been used topically for decades in the cosmetic field to prevent skin aging. So, researchers decided to put it to the test orally for skin cancer prevention. In a petri dish, skin samples taken from breast reduction and tummy tuck surgeries exposed to UV with or without niacinamide found that it enhanced DNA repair. Would this translate out into less cancer?

In a Phase II trial, dozens of individuals with four or more precancerous actinic keratoses each were randomized to take a placebo or 500 mg of niacinamide once or twice a day. Within two months, there was a 35 percent reduction in actinic keratoses in the twice-a-day group and a 15 percent reduction in the once-a-day group compared to placebo. It’s not that they developed fewer in those months, but more spontaneously disappeared in the niacinamide groups. What about actual cancers? By month four, there were five times fewer cancers (11 placebo participants developed 20 new skin cancers, versus only two niacinamide participants developing a total of four new cancers).

Normally, it would be difficult to fund studies on nonpatentable products that only cost a few cents a day, but the results of this and a similar study on organ transplant patients were so extraordinary ONTRAC was born. Oral Nicotinamide to Reduce Actinic Cancer was a publicly-funded phase III trial randomizing hundreds of people with personal history of skin cancers (actinic means UV-induced) to 500 mg of nicotinamide twice daily, or placebo for a full year. By the end, there were 25 percent fewer cancers, with no significant side effects, for just pennies a day. You have to keep it up, though. At a six-month follow-up after the study was over, the cancer rates equalized back to baseline rates.

What are the downsides? A study of 500 people put on up to three grams of niacinamide a day for five years (to try to prevent type 1 diabetes) unearthed no adverse effects over placebo (though it failed to prevent type 1 diabetes).

The high tolerance of niacinamide is partly due to its water-soluble nature, such that you just pee out any excess. But those with end-stage kidney failure on dialysis don’t have functioning kidneys, and so, blood levels should be monitored, as, in that context, niacinamide can cause a serious, though reversible, drop in platelets, which are important for blood clotting. High enough doses may become toxic to the liver, though, even with normal kidneys. Vasodilatory side effects like facial flushing, attributed to niacinamide in some older studies, were likely due to a less purified form contaminated with residual niacin. (I know it’s confusing! Niacin, also known as nicotinic acid, is a precursor of, but very different from, niacinamide, which is synonymous with nicotinamide.)

One concern regarding any treatment for a largely lifestyle disease is that individuals may neglect other defensive measures, overconfident in the supplement’s protection. Regarding drug interactions, a concern has been raised about taking niacinamide together with carbamazepine, a popular anti-seizure drug (sold as Tegretol). But, in general, as the ONTRAC researchers concluded, “Oral nicotinamide is a safe and effective in reducing the rates of new nonmelanoma skin cancers and precancerous growths in high-risk patients.” To their credit, a 2021 survey of skin cancer surgeons found that three-quarters recommended its use.

Other than nicotinamide, how else might we protect against skin cancer from the inside out? That’s what I’ll cover next.

Millions of skin cancers are diagnosed every year––the most common cancer in the United States. I’ve covered the single most important thing we can do—protect against exposure to UV radiation. What about dietary protection?

The first study to elucidate the effect of diet on UV-induced tumors found that high-fat diets accelerated tumor formation in mice. Within six months of UV, 50 percent of the high-fat-fed mice had tumors, compared to only 16 in the control-fed group. Encouragingly, switching the mice to a low-fat diet after the exposure was able to negate the tumor-exacerbating high-fat effects.

In people, a dietary pattern characterized by meat and fat consumption was associated with up to a near quadrupling of squamous cell carcinoma risk, the second most common type of skin cancer, whereas a vegetable and fruit pattern was associated with a halving of risk (apparently driven largely by the intake of greens). All we needed now was to randomize people to low-fat diets, and see if cancer could be prevented in people too. And, thanks to National Cancer Institute funding and a Veterans Affairs research team, the striking results were published in the New England Journal of Medicine.

Seventy-six patients with a history of skin cancer (and, therefore, at high risk of developing more) were randomized to continue to eat their regular diets, or switch to a “low-fat” diet of 20 percent of calories from fat. I put low-fat in quotes because that’s actually a high-fat diet compared to what’s normal for our species. For millions of years, our ancestors may have evolved getting approximately 10 percent of our calories from fat. For millions of years, about 99.8 percent of our time on Earth, it was virtually impossible for us to consume regularly more than 10 to 15 percent of calories as fat. So, that’s a normal-fat diet for the human species. A low-fat diet would be less than that––though 20 percent is certainly comparatively low-fat, compared to the current adult average in the United States of 37 percent. Would a drop down to 20 make a difference?

Researchers tracked the appearance of actinic keratoses––rough scaly patches that are premalignant lesions that turn into skin cancer––over the next two years. The average patient in the control group developed 10 lesions in those two years, compared to just three in the lower-fat group. Okay, but what about actual skin cancers? The results were so exciting the same team of researchers randomized a hundred skin cancer patients to the same two diets. By the end of the study, the skin cancer rate was 10 times lower in the lower-fat group.

This is no clarion call for SnackWell’s cookies. Although fat appears twice as bad, high-refined carb consumption was also found to be significantly associated with skin wrinkling and atrophy among a nationwide cross-section of middle-aged women. Those who consistently have higher than normal fasting blood sugars are perceived to be nearly a half year older than they really are, for every 18 points higher their average blood sugars are. So. those with a prediabetic fasting blood sugar of like 120 mg/dl look about a year older than those regularly having a normal fasting blood sugar, around like 75.

Now, the Women’s Health Initiative randomized nearly 50,000 postmenopausal women to a recommendation to eat the same lower-fat diet; yet, there was no change in the incidence of skin cancer. This is not surprising, given the poor adherence. Only 31 percent of the women in the intervention group complied with the dietary recommendation. It turns out healthy diets may only work—if you actually eat them.