Dr. Michael Greger asks in his NutionalFactd.org blog, “What are the effects of dairy products, sugar, and chocolate on the formation of pimples?”
He answers: Acne affects nearly one in ten people globally, “making it the eighth-most prevalent disease worldwide.” What is nutrition’s role? If we go back a century, dermatology textbooks “recommended dietary restriction”—for example, advising those with acne to avoid foods like “pork, sausage, cheese, pickles, pastries, large amounts of sweets, cocoa, and chocolate”—but old-timey medicine was full of crackpot theories. Dr. Kellogg, for example, blamed acne on masturbation. (Nothing a few cornflakes couldn’t fix, though!)
Population studies have found associations between acne and the consumption of foods like dairy, sweets, and chocolate. You don’t know if it’s cause and effect, however, until you put it to the test—which they did, as he discusses in his video Does Chocolate Cause Acne?.
There have been high-quality reports, like the Harvard Nurses’ Health Study, which looked at nearly 50,000 women, that found a link between acne and the intake of milk, particularly skim milk, during adolescence. This association has been found for teenage boys, as well. Researchers thought the hormones in milk might be responsible, but speculated it could also be the milk protein whey, which is added to skim milk to make it less watery and “might, therefore, play a role” in acne formation or as hormonal carriers. At 1:30 in his video, he discusses a case where whey protein powders were implicated in precipitating acne flares in teens who “had poor response to acne treatment regimens of oral antibiotics, topical retinoids, and benzoyl peroxide.” Their acne just didn’t seem to want to go away—until they stopped the whey supplementation. Could it just be a protein effect, though? It doesn’t seem so since soy protein supplements, for example, did not seem to cause the same problem.