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So far, they consider “there is inadequate evidence to estimate the benefits, if any, of vitamin D or calcium supplementation to prevent cancer and fractures” in “all noninstitutionalized adults, except postmenopausal women.” Among postmenopausal women, supplementing 400 or less IU of vitamin D and 1,000 or less mg of calcium daily led to a reduced risk of fracture only among people in institutional care. Among community-dwelling postmenopausal women, the research suggested risk of fracture may be reduced, but the finding was not strong enough for the panel to conclude that the benefits of supplements outweighed risks for this group. This led the task force to recommend against this group supplementing up to 1,000 mg of calcium and 400 IU of vitamin D daily.
The panel indicated evidence is inconclusive regarding possible benefits or risks of supplementing these nutrients in higher amounts for any group.
The task force used a process called meta-analysis—a technique in which data from many studies are combined and analyzed together—to consider existing research on vitamin D and calcium in relation to cancer and fractures. Of the 137 studies selected for review, 16 randomized controlled trials were deemed of sufficient quality to include in the final analysis. Nearly all of the participants in these 16 studies were postmenopausal women, 65 years old and up.
While the main takeaway of the task force’s study is the need for more research to better understand the relationship between these supplements and long-term effects on health, their finding of a weak association between these supplements and bone protection in postmenopausal women may point to the importance of knowing whether a person is deficient before supplementing.
Older people living in care facilities are more likely to be vitamin D deficient, so it makes sense that providing them with extra D can improve bone health. For adults who aren’t deficient, adding more vitamin D and calcium is unlikely to prevent fractures. The task force previously concluded that vitamin D supplementation is effective for preventing falls in older adults who are at increased risk for falls—an important benefit that should not be overlooked as people interpret these latest recommendations.
Although the report concluded that there isn’t enough evidence to determine whether higher doses protect against fractures in postmenopausal women or other healthy adults, some research does in fact suggest a benefit. For example, a meta-analysis of five double-blind trials that included a total of 9,292 people at least 60 years old found that supplementation with 700 to 800 IU per day of vitamin D3 reduced the incidence of hip fractures by 26%.
It would be interesting to see whether the task force’s conclusions would be different if more of the studies accounted for geography and lifestyle differences among participants. For example, a study of people living in Florida may be less likely to show a benefit with vitamin D supplements, because most people get enough D from being in the sun. This same study conducted in Minnesota may come to a different conclusion.
Dr. Bruce Hollis of the Medical University of South Carolina indicates that vitamin D, “has potential benefits in cancer prevention, cancer treatment, cardiovascular prevention, infection prevention, and prevention of autoimmune disease.” Finally, some health experts feel that giving supplements to younger women to prevent later bone fractures may be more effective than giving supplements to older women with already thinning bones.
These are draft recommendations, so stay tuned; they may change prior to finalization. While waiting for more solid results, keep in mind that research suggests these nutrients may play a role in the prevention of other diseases. Dr. Bruce Hollis of the Medical University of South Carolina indicates that vitamin D, “has potential benefits in cardiovascular prevention, infection prevention, and prevention of autoimmune disease.” To help you make smart decisions about calcium and vitamin D supplements, keep these tips in mind:
(Vitamin D and Calcium Supplementation to Prevent Cancer and Osteoporotic Fractures in Adults: U.S. Preventive Services Task Force Recommendation Statement DRAFT; http://www.uspreventiveservicestaskforce.org/draftrec3.htm)