Madison Park’s beach is a prime source of Seattle’s vitamin D intake.

Good news from the New York Times: “Given appropriate sun exposure in summer, it is possible to meet the body’s yearlong need for vitamin D.” Didn’t know you could store up the D like a battery, did you? (Fun fact: it’s actually a steroid hormone, not a true vitamin–if you get enough sun you don’t need another source.)

The consulting physician on the article, Boston U’s Dr. Michael Holick, suggests you take sun breaks “from 10 a.m. to 3 p.m. two or three times a week for 5 to 10 minutes.” Put sunscreen only on your face, and–think Lady Gaga–maximize your skin exposure.

What’s the big idea? Nutritionists have discovered that we aren’t getting nearly the amount of vitamin D that we need. While a serious vitamin D deficiency has long been known to cause rickets, it’s becoming more evident that chronic low levels of vitamin D can have serious health impacts as well.

Besides documented effects on bone health, Holick references studies that show a lack of vitamin D impacting multiple sclerosis, arthritis, type I diabetes, and immune response in general. Locally, the Fred Hutchinson Cancer Research Center has been researching vitamin D intake and colorectal cancer and breast cancer rates, and have also found that diet, geography, and lifestyle aren’t good predictors of individual vitamin D levels; a blood test is the best way to be sure.

Here’s the FHCRC line on vitamin D, what it does, how much you need, and how to get it.

While a blood serum level of 40 nanograms per milliliter of 25-hydroxyvitamin D is optimal–and easy to maintain if you’re outdoors frequently in sunshine–Holick says U.S. “Caucasians average 18 to 22 nanograms and African-Americans average 13 to 15 nanograms.”

Again, with sun, it’s easy. Holick says 15 to 20 minutes in the summer noonday sun can deliver the “equivalent to taking 20,000 IU of vitamin D orally.” (Yes, there’s a book.) If you start feeling droopy in winter, besides D3 supplements (1,000 to 2,000 IU day is the new, higher recommended intake), you can also feast on salmon regularly (360 IU per serving) or, better yet, halibut (510). Scroll down to see the food-derived vitamin D chart here.

One bonus of the sunbathing method is that your body knows when it’s manufactured enough D; if you’re increasing D levels via supplements, you can reach toxic levels. They’re very high, and not easy to get to, but some people do think that if x of a vitamin is good, 10x must be terrific. Constipation and nausea is nature’s way of correcting their math.