Pop Quiz: Which is more likely to give you acne, whole milk or skim?

You probably guessed “whole,” because whole contains more fat, and fat is, well, bad, right? That's exactly what Andrea L. Zaenglein, M.D., a professor of dermatology at Penn State Health’s Milton S. Hershey Medical Center, thought as well. And being a dermatologist, she should know.

...except that when she and the rest of her research team set out to prove that theory, they discovered a link between skim milk consumption and acne. What's more, the researchers found that wasn’t the case for people who drank full-fat milk, who are less likely to suffer from acne.

“I decided to do the study because I thought that acne being associated with skim milk made no sense,” she says. “I wholly expected for the study to show no association. When the results came in I was very surprised,” Zaenglein. The results of the team's study has been published by the Journal of the American Academy of Dermatology.

What's the science? Zaenglein says that it could be because the process of making milk fat-free removes some of the healthy components, particularly healthy fatty acids. “Vitamins A and D are also removed and then put back in but without the fat they may not be absorbed as well,” she says. As a result, your skin may not get all the good stuff it needs to stave off acne and stay clear.”

Acne, the plague of adolescence, affecting 80 to 90 percent of teens in the Western world, is a long-term disease that's caused by hair follicles becoming clogged with dead skin and oil. Much of acne is determined by genetics, but diet has long been suspected of playing a role as well.

Gary Goldenberg, M.D., medical director of the Dermatology Faculty Practice at the Icahn School of Medicine at Mount Sinai, connects the dots: “It's clear that diet and acne, as well as other skin conditions, are linked,” he explains. “We also know that foods that are natural — not full of hormones, antibiotics, and other chemicals are better.” Goldenberg suggests that people with adult acne switch to organic dairy and meats. “We know that dairy and meat products contain hormones, which may stimulate acne formation,” he says.