ANDREA SEABROOK, host:
Health advice can make your head spin. Drink milk, no, don't drink milk, low fat, no, low carb. Still, everyone aggrees you should always wear sunscreen. But wait! When we block out the sun, we're also blocking Vitamin D. It's this week's Science Out of the Box.
(Soundbite of music)
SEABROOK: Doctor Bruce Hollis is a professor at the Medical University of South Carolina. He studies Vitamin D, a nutrient our bodies create when we get out in the sun, and he says many of us just aren't getting enough. Thanks for coming in, Doctor Hollis.
Doctor BRUCE HOLLIS (Pediatric Nutritional Sciences, Medical University, South Carolina): You're welcome.
SEABROOK: So how does this work? How do we get Vitamin D from sunlight?
Dr. HOLLIS: The ultraviolet radiation hits your skin, and it causes this compound, which is a relative of cholesterols, called 70-hydrocholesterol, to break a bond, which forms, essentially forms Vitamin D. So then that gets absorbed across the capillary bed in your skin and into your circulation.
SEABROOK: Wow. So - and if you don't get the sun?
Dr. HOLLIS: Nothing.
SEABROOK: You don't get the Vitamin D?
Dr. HOLLIS: You don't get that conversion. It doesn't take place, and you get nothing.
SEABROOK: And equally if you wear sunscreen?
Dr. HOLLIS: It totally blocks it.
SEABROOK: What happens...
SEABROOK: What happens to people who don't get enough vitamin D?
Dr. HOLLIS: Well, the most acute thing that happens that we know is you end up with skeletal - thin bones, or we've known that for a long time. But the skeletal system seems to be the most sensitive to this, and what we're finding with vitamin D is that it's not one level fits all diseases. What we're finding is the skeleton needs relatively small amounts of vitamin D to function in somewhat of a normal fashion. Where, to prevention of cancer, the prevention of heart disease or cardiac - mild cardio infarction or auto immune seemed to be much higher requirements for the prevention of those diseases.
SEABROOK: So does it matter how light or dark a person's skin is?
Dr. HOLLIS: Everybody has the same capacity to make vitamin D. The difference is that the person of color needs more exposure for a longer period time to the light to make it happen. There's a professor, Nina Jablonski at Penn State University, who's actually studied this extensively, actually published a book, and her theory is that human beings actually in the northern hemisphere over 50,000 years lost their pigmentation because it would be detrimental to human reproduction because of not enough vitamin D and rickets in these northern latitudes.
SEABROOK: Hmm. OK, so somebody who's pasty white from sitting in the studio all the time, like me...
Dr. HOLLIS: You're going to make it quick.
SEABROOK: So I just run out and run back in, but somebody...
Dr. HOLLIS: That's right. You go out in a bathing suit for 10 minutes in the summertime in the sun, and you're going to make a ton. Actually, you can take the supplement early, and you'll have the same effect, and you don't need to worry about the sun. And in fact, that's how this problem probably has to be dealt with. It's not - you know, I don't want to fight with the dermatologist about the sun problems.
I mean, that's a whole - that's a ballgame, but you're talking about a problem that can basicly be solved by simple oral supplement that costs - essentially costs nothing. Vitamin D is dirt cheap.
SEABROOK: Dr. Bruce Hollis, a professor at the Medical University of South Carolina. Thanks very much for speaking with us.
Dr. HOLLIS: Thank you.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.