5/9/2012, 9:36 a.m.
The importance of vitamin D is a subject of ongoing debate. Researchers from Massachusetts General Hospital found that it may be vitamin D — not C — that keeps colds, the flu and other respiratory illnesses at bay. They noted that people with asthma and emphysema, for example, might be particularly susceptible to respiratory infections from vitamin D deficiency — an indication to some medical experts that it might also play a key role in the immune system.
Vitamin D is somewhat of an enigma. For starters, it isn’t a vitamin at all. Vitamins are organic compounds that the body needs but cannot make on its own. Rather, the body receives its vitamins from the food and liquids that we eat and drink.
Unlike other vitamins, vitamin D is made by the body, is found in very few foods, and, oddly enough, is actually a hormone.
Appropriately named the “sunshine vitamin,” vitamin D’s major source is the sun — ultraviolet B (UVB) rays to be exact — the same rays responsible for suntans, sunburns and skin cancer.
The American Academy of Dermatology warns against unprotected exposure to ultraviolet rays. The Academy declared “There is no scientifically validated, safe threshold level of UV (including UVB) exposure from the sun that allows for maximal vitamin D synthesis without increasing skin cancer risk.”
Dr. Deborah Scott, a dermatologist at Brigham and Women’s Hospital, says the sun is an excellent source of vitamin D. But everyone — including African Americans — must guard against excessive exposure. “There’s a balance between sun exposure and vitamin D,” she said.
But where that balance lies is a bit tricky. The times of exposure — and resultant vitamin D levels — vary by person, season, city and time of day.
Processing those sunrays is a group effort among the skin, liver and kidney. But in order for the process to work, the UVB rays have to be long and strong enough to pull off the job. And they are — from the spring through early fall. But in the late fall and winter, they are too short and that explains increased deficiencies during cold months.
A major biological function of vitamin D is to help the body absorb calcium and phosphorus. Calcium is stored in bones, but is a major workhorse throughout the body. It makes the heart work and muscles contract. If vitamin D does not do its job, the body “robs Peter to pay Paul” by taking calcium from the bones and using it elsewhere. The impact on bones can be devastating.
That’s why low levels of vitamin D are associated with osteoporosis, rickets in children and osteomalacia, or soft bones in adults. Fractures and falls are common in those lacking vitamin D.
The issue of vitamin D is of particular interest to blacks. Melanin — the substance that gives skin its color — provides a barrier to UVB in the skin. That does not mean skin of darker hues cannot make vitamin D — it just takes more time. While it may take whites and people with light skin about 10 minutes to process sufficient levels of vitamin D, it may require blacks closer to an hour.