Unlike most dermatologists, Dr. Michael Holick considers the sun a friend. As director of the Vitamin D, Skin and Bone Research Laboratory at Boston University Medical Center, Dr. Holick believes that many people have taken the ‘safe sun’ protocol to such an extreme that they’ve become deficient in vitamin D, a vitamin responsible for a number of critical functions in the body.

Vitamin D is perhaps best known for its role in protecting bone health. What’s lesser known about the vitamin is that low levels are associated with a higher risk of diabetes, hypertension, multiple sclerosis, rheumatoid arthritis, and breast, colon and prostate cancer. Dr. Holick, author of The UV Advantage, believes you can reduce your risk of these diseases by getting brief periods of sun – without sunscreen – for about ten minutes a day, a few times a week.

When you expose your skin to the sun for more than a few minutes, your body naturally makes vitamin D from UVB radiation. But a number of factors, including where you live, your age and skin type, the time of day and season, as well as cloud cover and smog influence how much vitamin D you make.

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If you live north of the 35-degree latitude line, running from L.A. to Atlanta, your body cannot make vitamin D from November through February, even if you go out at noon. For Canadians, that period extends from September to March.
Luckily, vitamin D is stored in fat, so your body can build up reserves in the summer and use it throughout the winter. But that only works if you get enough exposure during the summer. If you religiously avoid direct sun, apply sunscreen, and wear protective clothing, you may not be making enough vitamin D. Even a low SPF 8 sunscreen will prevent 90 percent of the vitamin’s production, and an SPF 15 prevents almost 100 percent.

Also, your ability to produce the nutrient decreases as you get older. By age 70, a person makes only one-fourth the vitamin D they could as a college student.

Sunshine, of course, is not the only way to get vitamin D. Natural sources include fatty fish and eggs. Vitamin D is almost always added to milk and breakfast cereal but is sometimes added to orange juice, soy and rice milk, hot cereal, yogurt and margarine. Supplements are another option.

The government currently advises an intake of 200 to 600 IU of vitamin D per day, though Holick and other experts believe that if you don’t get any sun, you need a daily minimum of 1000 IU.

The American Academy of Dermatology and the National Cancer Institute, of course, advise you to avoid the sun altogether and get your vitamin D solely from food and supplements. But the National Institutes of Health (NIH) supports the idea of safe sun exposure, stating that it can be difficult to obtain enough vitamin D from food. Their opinion is backed by a survey showing that 50 percent of younger and older women are not consuming the recommended amounts of vitamin D. And no wonder – a cup of fortified milk only contains 100 IU.

Whether you get your vitamin D from food, supplements or sun (or a combination of all three) is not critical. What matters is that you get enough. Here’s why.

Bone Health. Vitamin D improves the intestines’ ability to absorb calcium and phosphorous from your food, which in turn mineralizes your skeleton. Vitamin D also activates bone cells that build your bone framework, or matrix.

You may think you’re protecting your bones if you take a calcium supplement and eat a good diet, but if you’re low in vitamin D, you may only be absorbing a fraction of that calcium.

Let’s say you get 1000 mg of calcium each day from food and supplements. Without adequate D, you’ll absorb only 15 percent of the calcium, or 150 mg. Factor in the natural daily loss of another 200 to 400 mg in the gastrointestinal and urinary tracts, and you’re in the negative. Your body will draw that difference out of your bones, eventually causing osteoporosis, bone fractures or osteomalacia, a condition of muscle weakness and bone pain.

Prevent Cancer. Recent research shows that after sun exposure, the body synthesizes vitamin D and circulates it to the breasts, prostate and colon, where the vitamin appears to inhibit the growth of cancer cells.

This connection was supported in a 20-year study of 5,000 women in California that found that vitamin D from sun and diet decreased breast cancer risk. Further studies have confirmed that colon and breast cancer are more common in areas of the U.S. that receive little winter sun due to their northern locations and air pollution.

Lower Diabetes Risk. The possible link between vitamin D and diabetes is relatively new. At UCLA, researchers found that non-diabetics with low levels of vitamin D were much more insulin resistant, meaning that more insulin is needed for them to move sugar from the bloodstream to the tissues. If not addressed, insulin resistance can progress to Type 2 diabetes. This study also discovered that low level of D may reduce the ability of beta cells in the pancreas to secrete insulin. If beta cells stop functioning, Type 2 diabetics become dependant on insulin shots, and are no longer able to manage their disease through diet and lifestyle alone.

Lower Blood Pressure. Populations living closer to the equator have lower rates of hypertension than those living at more northern latitudes. Why? People living in sunnier locations make more vitamin D, allowing them to better absorb calcium, a mineral that helps maintain normal blood pressure in the arteries. This connection was illustrated in a 1998 study published in the Lancet showing that blood pressure was lowered in subjects who received UV light treatments three times a week.

Multiple Sclerosis. In animal studies, vitamin D prevented the formation of antibodies that attack the myelin sheath and cause MS. Though evidence of this in humans is circumstantial, MS risk is known to increase the farther you live from the equator.

But what about the hazards of sun exposure? Holick and others who subscribe to the get-some-sun theory emphasize that the idea is to expose yourself just enough to get the benefits, but not enough to burn, turn pink, or raise your risk of skin cancer or cataracts. While many doctors believe that any sun is dangerous, Holick believes that the benefits of a little sun far outweigh any slight – and, so far, unsubstantiated – increase in skin cancer risk.

So how much sun is safe? Dr. Holick recommends an average of ten minutes a day, two to three times per week on the arms and legs or face and arms. You may need more than ten minutes of sun if you have olive or dark skin, are a senior citizen, or live in the northern states. You’ll need less time if you live in the south or have fair skin that’s prone to burning.
If you decide to build up your reserves of vitamin D this summer, keep a few things in mind. At Lake Tahoe’s elevation, we get 18 percent more UVB radiation than at sea level. Sunlight is further intensified when it reflects off water, sand and concrete surfaces like skate parks and pool patios. Also, certain medications and herbs increase sun sensitivity; these include birth control pills, ibuprofen (Advil), some antibiotics and the herb St. John’s Wort.

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