Go to dairy link As summer heats up and people across America start slathering on the sunscreen, a note of caution is in order—a little sunshine is good for you.
Studies increasingly are suggesting the value of vitamin D—often known as the sunshine vitamin, because that’s one way you can obtain it—in everything from bone metabolism to maintaining muscle strength, immune function, reducing hypertension and possibly even playing a role in prevention of cancer and autoimmune disease.
“The old theory was that if you had enough vitamin D to prevent rickets and osteomalacia—two skeletal disorders—you were okay,” says Victoria Drake, a research associate in the Linus Pauling Institute at Oregon State University, and manager of its Micronutrient Information Center. “But new research now is raising our awareness about the possible relationships between vitamin D and cancer, particularly colorectal, breast, ovarian and prostate cancers. There also are potential links to cardiovascular disease and autoimmune diseases such as multiple sclerosis and rheumatoid arthritis.” .
What’s clear, however, is that many Americans are not getting even those minimal amounts, especially those with dark skin colors—in fact, one study reported that 42 percent of African American women were vitamin D deficient.
As a result, Drake says, many doctors are increasingly starting to test their patients for deficiency of this vitamin, especially in the temperate zones above 40 degrees latitude—a line running roughly from Philadelphia to Denver and through Northern California. That includes New York City, Boston, Chicago, Detroit, Seattle and many other highly populated cities. Residents of the Pacific Northwest, with its northern latitudes and eternally cloudy winters, are especially vulnerable.
“My own doctor said that he frequently tests for vitamin D status, and that vitamin D deficiency is prevalent in his patient population,” Drake says. “Experts are now talking about a phenomenon they call ‘Vitamin D Winter.’” One recent study referred to vitamin D deficiency as “a major unrecognized epidemic in the older adult population” and recommended routine blood testing for adequate levels.
Open to speculation, Drake says, is that deficiencies of vitamin D may have worsened in recent years as more people became aware of the risks of skin cancer and aggressively avoided sun exposure or used sunscreen lotions, on themselves and their children. Experts still agree that a fairly modest amount of sun is enough—perhaps 10-15 minutes of exposure on your arms and face about three times a week. Sunburn should of course be avoided.
Alternatively, you also can get vitamin D from some foods, including vitamin fortified milk and some cereals or breads—assuming you don’t have a diet rich in oily fish. For higher levels, supplements are usually necessary.
Among the recent findings and observations about vitamin D:
- Vitamin D is a fat-soluble vitamin that functions as a hormone in the body, regulatingcalcium metabolism.
- Most people living above 40 degrees latitude do not obtain enough vitamin D from about mid-November to early March.
- Infants who are exclusively breast-fed, and are not supplemented with vitamin D, are at high risk of vitamin D deficiency, because human milk generally doesn’t have adequate levels.
- People with dark-colored skin have significantly less ability to synthesize vitamin D from sunlight, as do the elderly.
- Obesity increases the risk of vitamin D deficiency because obese individuals cannot easily access the vitamin D stored in body fat.
So if adequate levels of vitamin D are critical to your health, how much is enough? Depends on who you ask, Drake says. The official government recommendation is 200 IU per day—although moderate sun exposure might provide about 100 times that much. Many multivitamins provide about 400 IU per day, and it’s generally accepted that levels up to 2,000 IU per day pose no health risk. Some studies underway with pregnant women are giving them 4,000 IU per day in supplements.
One study last year indicated an adequate level of vitamin D, produced by daily supplements of up to 2,000 IU per day, might prevent 30 percent of breast cancer cases and 50 percent of colon cancer cases in the United States—at extremely low cost and with few or no adverse effects.