The sun is the most natural vitamin D source, says Jason Miller, MD, a dermatologist at the Schweiger Dermatology Group in Freehold, New Jersey. Because as few as 20 daily minutes of exposure can cause wrinkles, sun spots, and increased risks of certain skin cancers, most derms and doctors suggest getting the nutrient from supplements, he explains.
Studies vary on the safe upper limit, but Miller says spending 10 SPF-free minutes in the sun is safe for most people. Talk to your doctor about whether you should take a D supplement on top of that.
The bottom line:
Even if it's overcast, get that exposure in the morning or late afternoon, when the sun’s rays are weakest. (Up to 80 percent of the sun's rays can pass through clouds.) If you'll be outside for any longer, apply a strong SPF. Those with fair skin or a family or personal history of skin cancer should always wear sunscreen.