If the sun burned out and all the cows died, pretty soon we’d all be walking around with rickets.
Happily, the sun is still shining and the pastures are still populated with grazing bovines. But rickets is still making a slight comeback, particularly among infants and young children.
Rickets is just the most obvious of the complications from a vitamin D deficiency, which means that you are getting less than the 400 IU Recommended Daily Allowance, or RDA.
That’s not much: 20 minutes in the sun produces up to 20,000 IU of D.
But the journal Pediatrics estimates 70 percent of American children are D-ficient – not to the point of complications, but still enough to get the attention of the medical profession.
Other symptoms of vitamin D deficiency occurring in young people, adults and seniors include “achy bones, achy joints, muscle fatigue and muscle weakness,” says Dr. Steven Joyal, vice president of scientific affairs and medical development for the Life Extension Foundation in Fort Lauderdale, Fla.
“They are somewhat unspecific, but all are signs of a vitamin D deficiency.”
According to the National Institutes of Health’s Office of Dietary Supplements, vitamin D also prevents certain cancers, as well as diabetes, hypertension, glucose intolerance and multiple sclerosis; wards off osteoporosis (with calcium) in older adults; and “modulates neuromuscular and immune function and reduction of inflammation” (in other words, colds, fever and flu).
There are also studies that indicate D-deficient diets are associated with lactose intolerance and milk allergies.
Vitamin D comes to humans in dairy products, fatty fish (salmon, catfish, tuna), broccoli, mushrooms and, mainly, sunshine. That’s why it’s called “the sunshine vitamin.”
But over the years, we’ve reduced our milk intake because of alarms about animal fat, and cut down on salmon because of mercury levels.
And as for that sunshine, just one word: melanoma.
Skin cancer is the most common form of cancer in the U.S., according to the Skin Cancer Foundation. One in five Americans will develop the disease.
Each year, there are more new skin-cancer cases than there are cases of cancers of the breast, prostate, lung and colon – combined.
Our educated cultural response has been to shield our vulnerable skin – and all of it is vulnerable – from the sun’s rays with sunblock and sunscreens.
Those chemicals, even the least expensive ones, are very effective in reducing the amounts of harmful UVA and UVB sunlight that penetrates the skin, some by as much as 97 percent. But there is little argument that those chemicals also reduce the amount of vitamin D that’s produced by the skin.
Dangerously so? “There’s a lot of discussion in the medical community,” Joyal says.
Dr. Bess Dawson-Hughes, director of the Bone Metabolism Laboratory at Tufts University, told the Boston Globe that “10 minutes a day of sun exposure to the face and arms without sunblock protection” is enough to trigger vitamin D production without increasing skin-cancer risk.
In his book “The UV Advantage,” Dr. Michael F. Holick at Boston University recommends “five to 15 minutes a day a few days a week” of sunlight exposure.
The idea is to not overdo it.
Dr. Mona Gohara, assistant clinical professor at the Department of Dermatology at the Yale School for Medicine, advises patients who are worried about being D deficient to “get tested (for vitamin D levels) so you know what you’re dealing with.
“If you are deficient, supplement your vitamin D with supplements and through your dietary intake, but do this so you are not giving yourself the extra risk of skin cancer by exposing yourself to the sun.
“A happy compromise,” Gohara says, “is to not live under a rock, go outside and enjoy your life but apply sunscreen diligently and avoid the sun when it’s at its highest, and be aware that vitamin D is important for your health and supplement it if you need to.”