Bones can benefit from minutes in the sun

Eating Well

March 31, 1998|By Colleen Pierre | Colleen Pierre,SPECIAL TO THE SUN

Late last year, Washington, D.C.'s Institute of Medicine released updated calcium recommendations that caused a nationwide media frenzy.

In the flurry of news stories, the new, higher vitamin D reference intakes were often overlooked.

Now, a New England Journal of Medicine study suggests we'd better get serious about the sunshine vitamin. Lots of people over 50 aren't getting enough, and that means greater risks for bone calcium loss and osteoporosis.

What's the connection? Vitamin D's job is to make sure you maintain a small amount of calcium in your blood to make your heart beat and control its rhythm, contract muscles, clot blood, heal wounds and create hormones and enzymes that control digestion and produce energy.

Vitamin D convinces your digestive system to absorb more calcium from the food and supplements you eat. If your diet falls short, or if you can't absorb the calcium there, your bones make the sacrifice and give up enough calcium to keep your heart and other vital parts working. Occasionally, this is OK, but do it day after day and your bones become weak and easily broken.

If you don't get enough vitamin D, "You might as well take a bath in milk as drink it," says Dr. Michael Holick, director of the Vitamin D, Skin and Bone Research Laboratory at Boston University Medical Center. Without vitamin D, you absorb only 10 to 15 percent of the calcium you consume. Get enough vitamin D and absorption triples.

Despite the fact that milk and fatty fish are among the few dietary sources of D, we've never worried much about it. That's because most of us make what we need when sun hits our skin. All it takes is 5 to 10 minutes, two or three times a week, with hands and face exposed and we're good to go.

So why the sudden concern? Knowledge, lifestyles and longevity have changed. We now know:

* Aging, getting a suntan and using a sunscreen all decrease skins' ability to make vitamin D.

* So does window glass. Sitting in a solarium may warm you, but doesn't make D.

* Where you live can be a problem, too. Folks from New York City northward can't make D for three or four winter months. (It is possible to make and store enough during the summer, but most older adults don't). Those from Atlanta south probably make enough all year round, if they get outside.

* You can't make D before seven or eight in the morning, or after four or five in the afternoon.

* Skin color counts, too. If you're fair, you make more D.

* For older adults, kidneys may not be as effective in changing skin-made D into its usable form.

The NEJM study did blood tests for vitamin D on 290 consecutive general medical patients in a Boston hospital. Of those, 164 were vitamin-D deficient. In many cases, the problem was inadequate vitamin D intake from food or supplements, winter season, or just not getting out of the house enough.

Several years ago I tracked my own travels and it scared me. I went out to run at 6 a.m., drove to and from work in my car, parked in a garage, crossed a covered bridge, worked inside all day, then didn't get home to play outside until after 6 p.m. I had no usable sun exposure until the weekends. That's when I started taking a multivitamin with 400 I.U.'s of vitamin D.

Now the IOM recommends 400 I.U.'s daily for adults 51 to 70 years old, and 600 I.U.'s daily for those over 70.

That's hard to do with food alone, unless you drink four to six glasses of vitamin-D-fortified milk daily.

Yogurt, cheese and ice cream don't count, because they're not vitamin D fortified. Be careful, though. Too much D from food or supplements is highly toxic. IOM sets the upper limit at 2,000 I.U.'s daily.

So check out your sunshine exposure. Your bones may need a boost.

Registered dietitian Colleen Pierre is the nutrition consultant to Union Memorial Sports Medicine Center and Vanderhorst & Assoc. in Baltimore.

Pub Date: 3/31/98

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