CHARLESTON, W.Va. -- Dear Cindy,

Every day it seems like I hear someone talking about vitamin D. Two of my friends were tested and told they are deficient. I am 47 and take a multivitamin with D in it, plus I take calcium, and it has D in it. I am going to be tested to see if I am deficient at my next doctor's appointment. Why is this such a problem all of a sudden? -- Dianne

Dear Dianne,

Though vitamin D was discovered 87 years ago by scientists at Johns Hopkins University, it has recently been a hot topic in both conventional and alternative medicine. This fat-soluble supplement maintains normal levels of calcium and phosphorus in the blood and must be present for your body to build a powerful steroid hormone called calcitriol.

We know vitamin D is essential for strong bones and teeth; it works in harmony with other nutrients in our body to support bone mineralization and demineralization. However, it plays a much bigger role in our health by aiding cell growth and regulating processes that keep our immune system running efficiently.

In fact, there are those who firmly believe that many chronic diseases and ailments such as depression, chronic pain, kidney disease, diabetes, osteoporosis, colon and breast cancer, cardiovascular disease and even the common cold could be treated with vitamin D. Others are not so quick to put it up on such a tall pedestal. Therefore, studies are continually being conducted to understand the full picture and scope of this vitamin.

Let's do some background work first. The magnitude of interest surrounding vitamin D is because studies are learning more about its benefits and recognizing that many and perhaps up to 90 percent of us are deficient today.

Why today? One obvious reason is sunshine. At a time when we are trying to limit our exposure to the sun, we are unfortunately blocking valuable doses of vitamin D, aka the sunshine vitamin.

Because our bodies cannot produce vitamin D on its own, we must get it through specific foods or allow 40 percent of our skin be exposed to sunshine a couple of hours a week. Hmm -- not so easy to do, particularly for anyone living north of about 35 degrees latitude, where sunshine is not so easy to find year-round. And why would anyone soak up the sun to get this nutrient and risk skin cancer and wrinkles? The benefit just doesn't outweigh the danger which raises the question:

How much do we need?

Unlike other vitamins, vitamin D has no recommended daily allowance, but it is assigned an Adequate Intake Value based solely on necessary amounts to keep bones healthy.

Adequate intake for people up to age 50 is 200 International Units a day. A typical multivitamin will contain 400 IUs. Most experts now agree that while this amount may prevent a skeletal disease known as rickets, it is insufficient. And when you consider the impact sunscreens and staying out of the sun has had on our levels, it seems plausible that these recommendations are obsolete and we need more from a supplement. The National Osteoporosis Foundation recommends a daily intake of 800 to 1,000 IUs per day for adults over age 50.

The American Academy of Pediatrics has doubled its recommendation to 400 IUs for infants and children. If you are between ages 51 and 70, you need 400 IUs. If you are over 70, you should have at least 600 IUs. This sounds like enough, until you realize that in the United States you get a whopping 1,000 IUs a minute from the sun. That's right -- 1,000 a minute!

So, obviously, if we are in the sun, we are taking in vast amounts without toxicity. It is surmised that our skin only takes in what we need when it comes from sunlight. However, when we ingest a supplement, it goes through the intestines and bypasses our skin's shutoff valve and subsequently may pose the risk of toxicity. This fuels the fire for debate, and the studies continue to sort out safe and effective dosage.

How much is safe?

The U.S. Food and Nutrition Board and the European Union's Scientific Committee on Food both agree that 2,000 IUs a day is where they draw the line for safe dosage. However, the debate continues as some studies show that adults need 3,000 to 5,000 IUs a day and others claim healthy adults can easily use up to 10,000 IUs a day.

Fascinating D facts

• There is a clear link between vitamin D deficiency and obesity, insulin resistance, heart disease, certain cancers, depression and osteoporosis.
• It is estimated that 80 to 90 percent of adults are deficient in vitamin D.
• You are less at risk for osteoporosis later in life if your mother had sufficient vitamin D while she was pregnant.
• Optimal bone growth and density during puberty may prevent osteoporosis later in life.
• Wild salmon, cod, sardines and fortified milk are the best food sources of vitamin D but 8 ounces of milk, for example, only supplies you with 100 IUs.
• Vitamin D is beneficial for everyone for our entire lifespan.
• As we age, our ability to absorb vitamin D decreases.
• Some believe that the required amounts of vitamin D vary from person to person.
• Your health-care practitioner is the only person who can tell you, based on a blood test, if you are deficient in vitamin D.

If you are concerned you may not be getting an adequate amount of vitamin D, see your physician. Despite all the discussion and debate on this valuable supplement, the only fact everyone agrees on is this: More research needs to be done.

Cindy Boggs, fitness presenter, author and Activate America director, has been an ACE-certified coordinator/instructor since 1989. Send your questions about fitness, training or health to YMCA of Kanawha Valley, 100 YMCA Drive, Charleston, WV 25311, or e-mail cindys...@aol.com. Look for Cindy's award-winning fitness advice book, CindySays ... "You Can Find Health in Your Hectic World" on her website, www.cindysays.com, or contact the YMCA at 340-3527.