Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
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, and just did a video on a supplement that might help. 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 new 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.
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