With an aging population, and with people living longer, experts saybone fractures will become a bigger and more costly problem unless moreis done to prevent them. Osteoporosis (reduced bone mineral density) ismost common in older adults, particularly women. It is a major riskfactor for bone fractures, which can cause significant suffering whilecarrying high economic costs. While vitamin D has been shown to reducethe risk of fracture in the elderly, a study recently published in theJournal of the American Medical Association (JAMA) raises the questionof how much vitamin D is enough.
The Recommended Dietary Allowance (RDA) of vitamin D for olderadults is between 400 and 600 International Units (IU) per day. Intheir review of the existing literature, a team of scientists includingsenior author Bess Dawson-Hughes, MD, director of the Bone MetabolismLaboratory at the Jean Mayer USDA Human Nutrition and Research Centeron Aging at Tufts University, found that this dose was not effective inreducing nonvertebral fracture rates among study participants. Theresearchers concluded, though, that higher daily doses, in the range of700 to 800 IU, may reduce the risk of fracture by approximately 25percent.
Dawson-Hughes and her colleagues analyzed the results of sevenexperimental trials that all compared fracture rates among subjects 60years of age and older given vitamin D supplements (with or withoutcalcium supplements) to those among similar subjects given only calciumor placebo. Each study lasted between one and five years, and lookedspecifically at hip fractures or other fractures that did not involvethe spine. The researchers found that only subjects receiving higherdoses of vitamin D supplementation had significantly fewer fracturesthan did subjects in the comparison groups.
"In the future, we may need to reconsider the currentrecommended daily values of vitamin D for older adults," saysDawson-Hughes. She adds, "We also need to look more closely at thepossible role that calcium supplementation may have in mediating theeffects of vitamin D. Fractures in the elderly can lead to severehealth consequences, including death. One promising prevention strategymay be dietary supplementation with both calcium and vitamin D."
Another meta-analysis on vitamin D published in JAMA last yearfound that older adults can reduce their risk related to falls by morethan 20 percent by ensuring they get enough vitamin D. Dawson-Hughes,an author on that paper, noted that "vitamin D may also improve musclestrength, thereby reducing fracture risk through fall prevention."
Bischoff-Ferrari HA,Willett WC, Wong JB, Giovannucci E, Dietrich T, Dawson-Hughes B.Fracture prevention with vitamin D supplementation: A meta-analysis ofrandomized controlled trials. JAMA. 2005;293(18): 2257-2264.
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