As sunshine disappears, it's time to take vitamin D

Soon, the sun will be merely a rumor for long stretches during waking hours, and darkness will dominate our senses and moods.

As if that weren't depressing enough, here's another grim thought: You most likely will become significantly deficient in vitamin D.

Vitamin D, the so-called "sunshine vitamin," can be absorbed either through the skin via ultraviolet-B rays — by far the most efficient, plentiful source — or through pills or fortified foods.

Once thought only beneficial for preventing rickets and other bone-growth issues in children, vitamin D has been shown to help prevent heart disease, various forms of cancer, kidney disease, diabetes and a host of autoimmune conditions ranging from multiple sclerosis to arthritis. And, yes, studies have shown it helps people suffering from seasonal affective disorder.

Just a few weeks ago, the American Academy of Pediatrics recommended doubling the amount of vitamin D children receive to 400 international units, though proponents consider those levels woefully inadequate.

Some scientific experts have gone so far as to call it a "super nutrient," eliciting skepticism from others who remember that appellation being given to vitamins C and E and beta carotene before extensive research reversed the thinking.

Count the National Institutes of Health's Office of Dietary Supplements among those still holding back judgment. In a position statement, the agency said vitamin D helps bone health in elderly men and women, but "for other age groups and health issues, it is too early to say conclusively whether more vitamin D may be beneficial."

Conversely, you can count the American Medical Association and the World Health Organization in asking for updated guidelines and saying that a significant percentage of American adults are vitamin D deficient.

Shedding some light locally is research from the U.S. Department of Agriculture's Western Human Research Center at the University of California, Davis, run by Charles Stephensen.

Stephensen, along with graduate student Laura Hall, recently presented findings on what is believed to be the first study looking at how much vitamin D that healthy adults, ranging in age from 20 to the mid-30s, receive from varying exposure to the sun during the four seasons.

The research followed 72 subjects in Davis split into four groups based on levels of sun exposure and degrees of skin pigmentation, Stephensen says.