Retirement age Americans derive 150 IU of vitamin D a day from their diet, on average (e.g. from tuna, salmon, D-fortified milk) – and without significant year-round sun exposure, this comes up at least 650 IU short of the very minimum needed to support resilient bone, new data confirm.
“Higher doses of vitamin D” support significant reductions in bone fracture incidence among aging adults, according to research at the USDA Human Nutrition Research Center on Aging at Tufts University – published July 5 by The New England Journal of Medicine (”A pooled analysis of vitamin D dose requirements for fracture prevention.”)
Higher than what?
At least higher than the Institute of Medicine’s current recommended dietary allowance of 600 IUs per day for adults up to age 70, and the typical vitamin D supplement dose of 400 IUs.
In fact, the Tufts team’s analysis of 11 randomized clinical trials investigating vitamin D supplementation and fracture risk in more than 31,000 older adults concluded that:
• “There was no benefit to taking Vitamin D supplements in doses below 800 IUs per day for fracture prevention," says senior author Bess Dawson-Hughes, MD, director of the Center’s Bone Metabolism Lab.
• While on the other hand, “Taking between 800 IUs and 2,000 IUs of vitamin D per day significantly reduced the risk of most fractures, including hip, wrist and forearm in both men and women age 65 and older.”
‘Gold Standard’ Analysis
As part of the study, Dr. Dawson-Hughes and colleagues divided the subjects into quartiles ranging from 0 to 2,000 International Units (IUs) of daily vitamin D intake.
In comparison with the other groups, the top quartile – getting 800 to 2000 IUs – sustained:
• 30% fewer hip fractures,
• And 14% fewer fractures of other bones.
Specifically, the team analyzed each participant’s vitamin D supplementation within and independent of the study protocol, controlling for age, vitamin D blood levels at baseline, additional calcium supplementation and whether the person lived independently or under medical care.
“Evaluation of individual-level data is the gold-standard of meta-analysis,” explains lead author Heike A Bischoff-Ferrari, MD, MPH, a visiting scientist from the University of Zurich. “Our results make a compelling contribution to the existing data on Vitamin D and fracture risk in men and women age 65 and older, whose vulnerability to bone density loss and osteoporosis leave them prone to fractures resulting from thinning bones.”
“Vitamin D supplementation is an efficient intervention for a costly injury that affects thousands of older adults each year,” adds Dr. Dawson-Hughes, who is also a professor at Tufts University School of Medicine. "The average recovery is long and painful and deeply impacts quality of life. After a fracture, older patients may only regain partial mobility, resulting in a loss of independence that is personally demoralizing and that can place added stress on family members and caregivers"
Financially, says Dr. Dawson-Hughes:
• Vitamin D supplements cost pennies a day
• Whereas the American Academy of Orthopaedic Surgeons estimated the cost of treating a hip fracture was $26,912 in 2007.
The results of the current study would be strengthened, says Dr. Dawson-Hughes, by large interventional trials investigating the impact of vitamin D supplementation on fracture risk. She and her colleagues also call for further investigation of the impact of combining calcium supplementation with high doses of vitamin D, as their data was inconclusive.
About the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University
For three decades, the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University has studied the relationship between good nutrition and good health in aging populations. Tufts research scientists work with federal agencies to establish the USDA Dietary Guidelines, the Dietary Reference Intakes, and other significant public policies.
Source: Based on Tufts University Health Sciences press release, Jul 5, 2012