Drinking extra amounts of milk in the adult diet.

Researchers claim to have found a correlation between milk intake and the incidence of acne. It seems milk drinkers develop more severe acne than non-milk drinkers. One study, published in the May 2008 issue of the Journal of the American Academy of Dermatology, looked at the diets of teenaged boys. The young men who drank the most milk also tended to have the worst acne. (Basnet, pp973-977)

This supports the results of previous studies, during which teenage girls were asked to keep food diaries and monitor breakout activity. Again, girls whose diets were rich in dairy products had more severe acne than the rest.

Of all dairy products, milk was the worst offender. Chocolate milk, cottage cheese, and sherbet also had a negative effect on the skin. But other dairy products didn't seem to cause breakouts.

Interestingly, skim milk induced breakouts more often than whole milk, so it seems fat content in milk isn't the culprit. And those who took vitamin D supplements didn't have more breakouts, so vitamin D isn't thought to be the cause either.

Fatty foods also didn't trigger breakouts. And the foods that many people associate with causing acne -- chocolate, pizza, soda, and French fries -- didn't seem to increase breakout activity at all.

Why would certain dairy products contribute to acne? Some think it's the hormones found in milk. Milk contains androgen hormones, which have long been associated with the formation of acne breakouts.

Testosterone is an androgen hormone, and it is strongly linked to acne development. It's most often thought of as a male hormone, but women produce testosterone too, although in lesser amounts.

Testosterone, through a complicated chain reaction, creates di-hydrotestosterone (DHT). DHT stimulates the sebaceous glands, creating an oilier skin that is more prone to pore blockages and, ultimately, pimples. Milk naturally is filled with hormones, including DHT. It's possible that milk contains enough hormones to have an effect on the body, including the skin. People who are genetically predisposed to acne breakouts may have a stronger reaction to the hormones in milk, according to some researchers. (Oftedal, pp225-252)

Many dairy farmers also give their cows additional hormones to stimulate milk production and enable the cow to produce more milk. As a result, most milk is very high in IGF-1. IGF-1 is a growth factor that peaks in the human body during adolescence, when acne is usually at it's worst. It is believed that IGF-1, along with testosterone and DHT, trigger acne breakouts.

In two previous studies, high milk consumption was linked to high IGF-1 levels. Again, skim milk was associated with higher IGF-1 levels than whole milk.

The processing of skim milk may explain why it is linked to acne severity more often than whole milk. Whey proteins are added to give skim milk a creamier consistency. Some speculate that these proteins impact acne development.

Of course, not everyone who drinks a lot of milk breaks out in pimples, and many disagree with these findings. The Dairy Council counters that the results are skewed, ...