True or false: In order to avoid skin cancer (and wrinkles!), it’s important to slather on sunscreen before so much as stepping out in the summer sun.
… True! Well, almost true. Wearing sunscreen—and the right sunscreen, at that—is still vitally important for both cancer and wrinkle prevention. But it’s equally important to skip the sunscreen sometimes, and the reason comes down to vitamin D.
Sometimes called “the sunshine vitamin,” D is the only vitamin our bodies actually synthesize from sunshine. Because there are very few food sources of vitamin D, sunshine (or supplementation) are crucial to getting an adequate amount.
Without an adequate amount, all sorts of trouble can transpire inside our bodies. Vitamin D deficiency has been linked to weight gain, depression, arthritis, auto-immune disorders, severe asthma and heart disease, to name a few things. Conversely, high levels of vitamin D are associated with decreased breast cancer risk, stronger teeth, improved moods and a well-functioning immune system.
To get enough vitamin D, you need to get enough sunshine—but not just any kind of sunshine. Vitamin D synthesis in the skin is only triggered by ultraviolet B (UVB) rays. The sun produces both UVB and UVA rays, and UVB is rarer. The sun only omits UVB light between about 10:30 a.m. and 4 p.m.—sun exposure outside of this time frame won’t net you any vitamin D.
Sunscreen is also an impediment to UVB exposure. After all, that’s what it’s designed to you: Block the skin from absorbing potentially-harmful radiation from the sun. But if you want to produce vitamin D, your skin needs to get at least a little of that UVB exposure. In other words, it’s important to skip the sunscreen for a small portion of sunlight exposure.
The amount of time you’ll need (during UVB hours, without sunscreen) to produce enough vitamin D depends on several factors, including your skin type, your location and the “UV Index” (a measure of how strong the rays are) that day. Your skin type is an especially important determinant, which you can figure out using the Fitzpatrick Skin Typing chart.
Knowing your skin type, you can approximate how much sun exposure you need for vitamin D purposes. Someone with skin type 1 might only need 10 to 15 minutes sunlight (with at least half their skin exposed) most days to make enough vitamin D. Someone with skin type III, however, might need 40 or more minutes regularly to produce the same amount; and someone with skin type VI could need almost two hours.
Regardless of skin type, the more skin exposed means less time needed in the sun.
If getting enough sun exposure isn’t feasible for you—or you just don’t want to risk any time in the sun without sunscreen at all—consider taking a regular vitamin D supplement. For men and women 19-50 years old, the recommended dosage is 600 IU. You can also get vitamin D from cod liver oil, swordfish and salmon; and marginal amounts from foods such as mushrooms, fortified orange juice and cereals, beef liver and sardines.