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How Much Vitamin D Is Too Much in Older Adults

Jacobson, Joy

Section Editor(s): Pfeifer, Gail M. MA, RN

AJN The American Journal of Nursing: August 2010 - Volume 110 - Issue 8 - p 15
doi: 10.1097/01.NAJ.0000387673.66565.4c
In the News

A single massive dose apparently increases fall and fracture risks.




In the arsenal against falls and fractures in the elderly, vitamin D is regarded as a principal weapon. But many older adults are deficient in the vitamin: often, they have less sun exposure than is needed to maintain adequate levels and find it difficult to remember to take supplements regularly.

Australian researchers sought to sidestep such hurdles by testing the effects of an annual vitamin D megadose. They found that a 500,000-IU dose of vitamin D3 (cholecalciferol) given yearly for three to five years actually increased the risk of falls and fractures in noninstitutionalized women 70 years of age and older.

Sanders and colleagues recruited more than 2,300 women with a risk of hip fracture triple that of average community-dwelling women of the same age. The women were randomized to receive either the vitamin D3 megadose (in 10 daily 50,000-IU oral doses) or a placebo. Doses were given in autumn or winter, to compensate for expected decreases in serum levels during those periods. Women kept track of falls and fractures on a monthly calendar for a year from the last dose; researchers followed up by telephone.

Women in the vitamin D group had 15% more falls than women in the placebo group (2,892 versus 2,512, respectively) and 26% more fractures (171 versus 135, respectively). The likelihood of fractures and falls peaked in the first three months after each megadose was given; for that reason the researchers speculate that the elevated risks were dose related. The authors of an accompanying editorial theorize that a megadose might cause a huge release of the enzyme that catabolizes vitamin D, resulting in lowered levels in tissues and a consequent increase in the risk of fracture. Moreover, the subjects receiving vitamin D may have felt better and become more active than they would have been otherwise, leading to an increased risk of falling.

But nurses shouldn't infer from these findings that vitamin D supplementation is unsafe, cautions Rose Ann DiMaria-Ghalili, a researcher in the nutrition of older adults and an associate professor of nursing at Drexel University. She told AJN, "We're going to see a lot more work on the importance of vitamin D, but we have to find out what's the safest dose and what's the best way to give it to ensure compliance."

She recommends that older patients have their serum vitamin D levels checked and work with their primary care providers to avoid or correct deficiencies.—Joy Jacobson

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FastSTATS from the American Cancer Society

  • 1 in 5: The number of deaths attributed to tobacco use in the United States.
  • 30%: The approximate annual percentage of U.S. cancer deaths that are associated with poor nutrition and physical inactivity, including excess weight.
  • 32,050: The estimated number of U.S. men who will die from prostate cancer in 2010.

All statistics from Cancer Facts and Figures 2010.

Sanders KM, et al. JAMA 2010;303(18): 1815–22;
    Dawson-Hughes B, Harris SS. JAMA 2010;303(18):1861–2.
      © 2010 Lippincott Williams & Wilkins, Inc.