Construction workers, landscapers and farmers may have a leg up on office workers when it comes to bone health, according to research on the positive effects of sun exposure.
Historically, Americans worked outdoors tending their fields or participating in other manual labor under the sun. In modern times, many careers require work under artificial light, causing an increase in vitamin D deficiency.
Centers for Disease Control and Prevention has reported that the percentage of adults achieving a proper level of vitamin D has declined from about 60 percent in 1988-1994 to approximately 30 percent in 2001-2004. According to a Mayo Clinic Study, 25 to 50 percent or more of patients commonly encountered in clinical practice are deficient in vitamin D.
Dr. David Shinstrom at The Orcas Family Health Center says it is entirely possible that “low vitamin D levels have been present in humans since we stood on two feet.”
Vitamin D is fat-soluble and known as “the sunshine vitamin.” Studies have shown that it promotes bone health, cell growth, immune function and reduces inflammation, according to the National Institutes of Health.
Shinstrom says using vitamin D with calcium has been successful to treat osteoporosis, but he is skeptical about its role in other health issues. He describes the vitamin as one of the “more controversial topics in the medical field, with a wide variety of opinions.”
“There are always new studies that may provide more proof,” he added.
Sources of vitamin D
According to the National Institutes of Health, vitamin D is found in fatty fish like salmon and tuna. It can also be found in butter and cheese, said Dr. David Russell of Orcas Island Family Medicine.
According to the Global Healing Center, dried versions of shiitake mushrooms are high in vitamin D. This may be due to the fact that they are adept at sucking up sunlight. But food is not the ideal source. The best way to get vitamin D is from Mother Nature’s sunny rays.
For Northwest residents, who don’t have the luxury of year-round sun, Russell suggests looking at labels to see what you may be getting already in your diet and to use a supplement if you’re not getting adequate vitamin D, especially in the wintertime. Russell said the current recommended daily allowance of vitamin D nationwide is 600 to 800 IUs daily.
“However, as we live in the northern part of the United States, the degree of sunlight that we receive would generally be less than other parts of the country, so I have generally recommended that adults here take between 1,000 and 2,000 IUs,” he said.
When is it enough?
According to Steve Blake in his book “Vitamins and Minerals Demystified,” “Fifteen minutes of summer sun in a bathing suit makes an average of 20,000 IUs of vitamin D—100 times the adequate daily intake. Since vitamin D is stored for long periods, this may be enough vitamin D to last for 100 days.”
C.F. Garland wrote in the British Medical Journal that the storage form of vitamin D has a half-life of approximately three weeks, so people in northern latitudes become deficient by December if they are relying solely on the sun for their vitamin D. That’s when they can start supplements.
But residents of sunny climates are also commonly found to be deficient in vitamin D, due to cultural habits and/or dress, according to the Mayo Clinic study.
Some of the risks
Shinstrom said 15 to 20 minutes of sun a day will provide adequate vitamin D, so supplements are unnecessary. He added this amount of time “is not a sufficient exposure to raise a concern about skin cancer. Having this sun exposure is a good reason, in addition to several others, to go for your daily walk.”
Martin Mittelstaedt, author of “The Vitamin D Miracle: Is It For Real?” recommends applying sunscreen after spending five or 10 minutes in the midday sun, then apply as normally directed. This brief amount of exposure is enough to synthesize a few weeks’ worth of vitamin D.
Mittelstaedt says, “the benefits of modest sun exposure in preventing serious, hard-to-treat cancers outweighs that risk.” But Russell’s opinion is this conclusion should be made on a much more of a personal, case by case situation.
“Weighing the risk and benefit of additional sunlight exposure versus vitamin D supplementation is a topic best taken up individually with a person’s doctor,” he said.
