Time in the Sun: How Much Is Needed for Vitamin D?

How much sun is it safe to get without sunscreen?
It's difficult to quantify how much since skin pigmentation affects how much radiation your skin absorbs: The darker the skin, the more it's protected against skin cancer but the less able it is to absorb UV-B rays. It also depends on how much skin is exposed and the time of day. If you're fair skinned and sunning yourself outside in a bathing suit at noon, you only need a few minutes without sunscreen. If you're already tan or of Hispanic origin, you need maybe 15 to 20 minutes. Black skin may require six times the sun exposure to make the same vitamin D levels as a very fair-skinned person, but we need more research on this because the studies that have suggested this have been small. We're starting a study later this year to establish how much skin pigmentation, clothing, sunscreen, and seasonal change affect vitamin D levels, so we should know more about all of this in the near future.

Can I make vitamin D driving in my car on a bright, sunny day on my way to work?
No. For one thing, UV radiation doesn't penetrate glass; that's why you can't get a burn or tan if you're driving with your windows closed. (The heat you feel is infrared radiation from the sun, which doesn't have any health impact beyond making you overheated or causing sunstroke if you get an excessive amount.) Even if you're driving in a convertible, though, you probably won't get a good dose of UV-B rays if you're driving in the early morning when the sun is still low in the sky. Talking a stroll during lunchtime is your best bet.

Join the Discussion: Do you think you get enough sun or have you been scared into the shade? Our friends at Betty Confidential want to know.

Tomorrow: Benefits of Sunlight Extend Beyond Vitamin D