For years we've heard:
Get out of the sun or at least use sun block, or you'll get skin cancer.

Now, we're hearing:
Get in the sun at least for a short time, or your bones will break!

Who knew? Doomed to biopsies if you do; destined for fractures if you don't.

Here's the dilemma: As sure as the sun will come up tomorrow – and cause melanoma – we also must have vitamin D to process the calcium needed for strong bones. And the major source of vitamin D is the sun.

"The issue of sunscreen and vitamin D is somewhat controversial. But the fact is that you need vitamin D to help you absorb calcium, and you need calcium for your bones. That's not debatable," says registered dietician Alison Gernand, at The University of Texas School of Public Health at Houston.

Vitamin D's Role

The body makes vitamin D in the skin after direct exposure to sunlight. Vitamin D allows calcium to enter the bloodstream from the intestines and helps the kidneys reabsorb calcium that might otherwise be excreted. It also maintains the concentration of calcium in the blood and interacts with bone cells to promote mineralization.

The Houston dietitian added that, in the U.S. where 9,800 people died of skin cancer last year and incidence of malignant melanoma is about 54,000 new cases a year, sun protection is still a health priority.

Why Worry

Today, the constant use of sun blocks raises concerns about whether people are getting enough vitamin D to process calcium needed for their bones. This concern is heightened in:

• Exclusively breastfed infants
• Children 9 -18 years of age, whose bones are rapidly growing
• Women who will be adding important bone mass up to their early 30s
• Adults over 50 years
• Housebound people or those who seldom go outside

In general, Gernand explains, bone density peaks somewhere between the age of 20 and 30, and this bone mass is the basis of skeletal health in later years. However, past this age is not the time to forget about your bones. In fact, vitamin D requirements increase as you age. Women especially should continue to be concerned with bone health even after 30. This bone mass is the basis of skeletal health in later years.

Women, young or old, should strive for bone health regimen including:

• Healthy, balanced diet
• Weight-bearing exercise
• Vitamin D along with calcium

Some women as young as 40 begin to lose bone mass as part of the aging process. A younger woman who smokes, has experienced broken bones or has low body mass index is also at risk and should consider a bone density test. The bone scans used at health fairs are useful indicators, according to Gernand, although if you think you're at risk, it's best to discuss this with your physician.

How Much is Enough?

Just 10 to 15 minutes 2 to 3 times a week of sun exposure on your arms and face will probably provide enough vitamin D to process calcium. If you live closer to the equator, the sun is more intense.

Time of day, as well as skin color affect vitamin D production. The fairer you are, the more vitamin D you produce when exposed to the sun. Sun blocks, air pollution, clothing and window glass all block the sun's UV rays and negatively affect the production of vitamin D.

The best strategy is to get only small amounts of unprotected sun exposure in the morning and evening, when the sun is less intense. Gernand cautions that if you plan to be in the sun more than a few minutes in the middle of the day, especially in the summer, you should always use sun protection. Parents should take special care to prevent children from getting sun burns.

Although vitamin D is found in some foods such as fortified milk and cereals, egg yolks, tuna, salmon and liver, the major source is the sun. Gernand says it is almost impossible to overcompensate through these natural sources. Some people, especially the elderly and breastfed infants, may need to take a supplement containing vitamin D to ensure that their daily intake reaches 200 to 600 international units.

Be careful with supplements, though, since excess vitamin D is not passed through the body but stored in fat and the liver and can be harmful.

Our capacity to store vitamin D is a double blessing: it allows us to draw on a vitamin D bank account in the winter, when sun is hard to come by.

Add a Little Sunshine

Sunshine is helpful in avoiding other health problems such as "Winter Blues" known also as seasonal affective disorder.

And a recent Australian study surprisingly found that adults who got the most sun exposure during their off-work hours had the lowest risk of non-Hodgkin's lymphoma, suggesting that moderate absorption of vitamin D helps protect against some types of cancer, too.

Last Updated: 6-03-2004

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