Vitamin D: Vital Role in Your Health

Vitamins like C and E continue to be the darlings of many supplement lovers. But those vitamin superstars are being forced to share their throne with the long neglected vitamin D, which is finally getting the attention it may have always deserved.

No doubt, you're probably familiar with the role of vitamin D in promoting healthy bones, largely by promoting the absorption of calcium. "If you have a vitamin D deficiency, particularly in your older years, it can lead to osteoporosis or osteomalacia [bone softening]," says Lona Sandon, RD, assistant professor of clinical nutrition at the University of Texas Southwestern in Dallas.

But there is recent and mounting evidence that links low levels of the vitamin to an increased risk of type 1 diabetes, muscle and bone pain, and, perhaps more serious, cancers of the breast, colon, prostate, ovaries, esophagus, and lymphatic system.

If you want to lower your blood pressure, vitamin D may be just what the doctor ordered. If you're trying to reduce your risk of diabetes, or lower your chances of heart attacks, rheumatoid arthritis, or multiple sclerosis, then vitamin D should be at the front of the line in your daily supplement regimen.

D-fense for Your Health

As the research into vitamin D is accumulating, it's hard to know where the accolades should start. "Activated vitamin D is one of the most potent inhibitors of cancer cell growth," says Michael F. Holick, PhD, MD, who heads the Vitamin D, Skin, and Bone Research Laboratory at Boston University School of Medicine. "It also stimulates your pancreas to make insulin. It regulates your immune system."

Just consider these recent studies:

Your D-Day Plan of Attack

Many vitamin D researchers are convinced the government's recommendations for adequate vitamin D intake are far below what your body really needs. Those guidelines call for 200 IU a day up to the age of 50, 400 IU from 51 to 70, and 600 IU over age 70.

But, says Holick, studies show that to achieve blood levels of vitamin D that can protect you against chronic diseases, you need an optimal dose of 1,000 IU of vitamin D a day. The vitamin is well absorbed from foods like fortified milk and from vitamin pills, whether taken alone or in combination with other foods.

So how can you get enough of this overlooked vitamin? Most foods aren't filled to the brim with vitamin D -- far from it. You can get 425 IU in a 3-ounce serving of salmon, and 270 IU in 3.5 ounces of canned sardines. But most foods provide much more modest amounts of vitamin D, from egg yolks (25 IU per egg) to cheddar cheese (2.8 IU per ounce).

"You'll get 200 IUs of vitamin D by drinking two glasses of fortified milk," says Sandon, spokeswoman for the American Dietetic Association. But at age 70, even reaching the government's recommended level of 600 IU from diet alone can be a challenge. "These people are probably not drinking six glasses of milk a day for various reasons, including a higher incidence of lactose intolerance in the elderly," she tells ishonest.

"We need more food fortification [with] vitamin D," says Susan Sullivan, DSc, RD, assistant professor in the department of food science and human nutrition at the University of Maine. "We need to make it easier for people to meet their vitamin D requirements through the food supply."

Some of that fortification is already happening. In addition to milk, a growing number of food manufacturers are adding vitamin D to yogurt, breakfast cereal, margarine, and orange juice. A cup of fortified orange juice, for example, contains 100 IU of vitamin D.

Here Comes the Sun

If you're striving for Holick's recommendation of 1,000 IU a day, you may have to turn to vitamin D supplements or the sun as your vitamin D savior. Regular sun exposure can stimulate the human skin to produce quantities of vitamin D that far exceed your needs. Without a shadow of a doubt, sunlight is the largest single source of vitamin D for most people.

But before you grab the beach towel and head for the seashore, keep in mind that particularly in the higher northern latitudes, vitamin D levels can be problematic. If you live above 40 degrees north latitude -- north of Philadelphia, for example, or Denver -- you won't make much of any vitamin D in the winter.

That kind of sun scarcity can take its toll on human health. "There is some striking evidence that as you go farther north, the incidence of certain kinds of cancer increases," says Sullivan. "There is more prostate and colon cancer in the north than in those who live closer to the equator."

The correlation is similar for multiple sclerosis. Research has shown the immune disorder is more common in areas with fewer hours of sunlight. For example, multiple sclerosis is more common in Canada and the northern states of the U.S. than in the southern states.

The Perils of Sun Worshiping

The sun isn't all good, of course. As any dermatologist will eagerly tell you, too much sun could risk a lot more than a bad sunburn. Routinely overdosing on sunshine could translate into life threatening skin cancer. On the other hand, if you're completely sun-phobic from sunrise to sunset, you may pay the price in the amount of vitamin D your body produces, cautions Holick, author of The UV Advantage.

So how much sun do you dare expose yourself to? Holick has calculated that if you sun yourself in a bathing suit long enough to produce slight redness of the skin, you'll produce the equivalent of 10,000-25,000 IU of oral vitamin D.

"Let's say you're on Cape Cod or a New Jersey beach in the summer," Holick tells ishonest. "Just five to ten minutes in the sun two to three times a week -- exposing your hands, legs, and arms -- is more than adequate to satisfy your vitamin D requirements, and you're not likely to significantly increase your risk of skin cancer in the process. Then after that five to ten minutes of exposure, put on a sunscreen of SPF 15 or greater for the rest of your time in the sun."

The good news is that you can't overdose on the vitamin D manufactured by your skin. But as for vitamin D in the diet and in pills, Sandon says that the upper limit is 2,000 IU a day. "Vitamin D is a fat-soluble vitamin, so it's stored in the body," she says. "If you're taking a supplement that puts your daily intake at more than 2,000 IU, you can get a toxic or overdose effect, which can possibly lead to kidney stones or kidney damage, muscle weakness, or excessive bleeding."

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