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Why Take Vitamin D?

Nearly every cell in the body interacts with vitamin D. The activity of many genes -- up to a third of the entire human genome -- is affected by vitamin D.

There's evidence that vitamin D deficiency may increase the risk of many diseases:

However, there's no hard evidence that taking vitamin D supplements prevents or treats any of these illnesses.

What the evidence does show is that vitamin D helps the body use calcium to prevent bone loss and to build stronger bones, and that vitamin D prevents falls in the elderly by improving muscle function.

A new study, reported at the annual meeting of the Endocrine Society by Weill-Cornell researcher Richard Bockman, MD, PhD, shows that people are seven times more likely to benefit from the bone drugs Actonel, Boniva, Fosamax, and Zometa if their vitamin D levels are at or above 33 ng/mL.

Why is there so little data on vitamin D and non-bone diseases? Only recently have researchers realized that vitamin D is not harmful at the new, higher doses. Few studies used enough vitamin D to raise blood levels of 25(OH)D above 30 ng/mL.

On the positive side, there is very little evidence that increasing vitamin D levels to 30 to 100 ng/mL is any harm to children or to adults -- except in some people with granuloma-forming disorders or lymphoma.

Recommended Vitamin D Doses

Last November, the Institute of Medicine (IOM) released guidelines suggesting that most Americans and Canadians get enough vitamin D, and recommending modest doses of vitamin D supplements. The new treatment guidelines point to new data suggesting that the IOM recommendations "may be inadequate."

The new guidelines recommend different doses of vitamin D for those at risk of vitamin D deficiency:

  • Age 0 to 1 year: 400 to 1,000 International Units (IU) daily
  • Age 1 to 18 years: 600 to 1,000 IU daily
  • All adults over age 18: 1,500 to 2,000 IU daily
  • Pregnant or nursing women under age 18: 600 to 1,000 IU daily
  • Pregnant or nursing women over age 18: 1,500 to 2,000 IU daily

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