ALEX CHADWICK, host:
This is DAY TO DAY. I'm Alex Chadwick.
MADELEINE BRAND, host:
And I'm Madeleine Brand.
Like teenagers, many of us roll our eyes at the idea that eating sugar gives us bad skin. Wasn't that just something our moms told us so we wouldn't eat chocolate? Well, it turns out maybe they were right. Dr. Sydney Spiesel is here now. He's a pediatrician and a professor at the Yale Medical School.
Syd, I thought that was just an old wives tale that eating too much sugar gave you acne.
Dr. SYDNEY SPIESEL (Yale Medical School): Well, it was an old wives tale for sure. Many people kind of believed it and there were some early studies that seemed to dismiss it. I think there is some question now in retrospect about those early studies.
BRAND: So Syd, there's new research out?
Dr. SPIESEL: Yeah, there is. It comes to us from Australia, where some researchers took a group of 54 acne patients - well, they were between 15 and 25 - and half were assigned a diet which provides what's called a low glycemic load; that is to say a diet that doesn't produce high levels of blood sugar. So it might be things that are like lean meat or fish or complex carbohydrates like whole grains. In short, what all of us would think of as a healthy diet.
The other half of the patients were told to just eat a diet which would give high blood sugar levels - a lot of sweets, a lot of highly refined starches. And then they looked to see what happened to these two groups.
BRAND: And the people who were eating Doritos and M&Ms, they had worse skin?
Dr. SPIESEL: Yes. They actually did have worse skin. The pictures of them were red-blinded by a dermatologist who didn't know which group they came from. And after 12 weeks it was pretty clear that the people who ate the better, healthier - so-called healthier diet - had better skin.
BRAND: So does that then prove it beyond a - beyond doubt that indeed bad diet equals bad skin?
Dr. SPIESEL: Well, it suggests that there is a relationship between diet and skin. But the authors of the paper wanted to say, well, it has to do with this something that causes high levels of blood sugar. But in fact, this diet had lots of effects on the young people who took it, the better diet. It had fewer calories. They lost weight. There was a lower intake of saturated fat. So the question in my mind is, is it just the sugar, the sugar load, or was it one of the other factors? But it does look like diet does make a difference.
BRAND: And what about stress and hormonal changes? I always thought that those were the big factors for bad skin.
Dr. SPIESEL: Well, you know, I think that all of those things clearly do have some effect. People get acne as hormonal levels change in puberty, for example. So it's clear that - or at least it seems very likely it isn't just diet. There's something else that are important - that's important. Stress plays a role. Acne is actually caused by changes in the fatty acids that are produced in the glands of the skin. And some of those changes are actually caused by a kind of bacterium which produces a very irritant product. And so the irritation, which is the result of this product, leads to acne.
So there are just so many different factors that lead to acne, it's hard to separate out one. But any one that will help, anything that will help, seems to me useful.
BRAND: That's opinion from Dr. Sydney Spiesel. You can read his Medical Examiner column at Slate.com.