Reports of the demise of vitamin D and calcium have been greatly exaggerated, say industry experts. Last week two medical studies sent the dietary supplements industry reeling, with reports that vitamin D and calcium had no effect on lowering the incidence of bone fractures in the at-risk population. But retailers and manufacturers who fear downwardly spiraling sales can take a close look at the studies to see that the findings apply to people who already have osteoporosis, not those trying to prevent it.
"There are hundreds of studies that show benefit from supplemental vitamin D and calcium for bone health," said Andrew Shao, Ph.D., vice president, scientific and regulatory affairs, at the Council for Responsible Nutrition. "These two studies were done in real specific populations [with results] that don't really apply to otherwise healthy populations who are taking their supplements for prevention."
In the more prominent of the two studies, published in The Lancet ("Oral vitamin D3 and calcium for secondary prevention of low-trauma fractures in elderly people"), people who had already had one fracture and had regained mobility were assigned to take calcium, vitamin D, a combination of the two, or placebo. After 24 months, the researchers noted, "The incidence of new low-trauma fractures did not differ significantly between those allocated vitamin D3 and those who were not, or between those allocated combination treatment and those allocated placebo."
Nor did those given calcium have a lower rate of new fractures than those given placebo. "The findings do not support routine oral supplementation with calcium and vitamin D3, either alone or in combination, for the prevention of further fractures," the researchers concluded.
The researchers noted, however, that participants had poor compliance with calcium tablets; nearly 36 percent had stopped taking the tablets by the time the study ended. "Almost half these folks didn't take their supplements," said Shao. "How firm a conclusion can you draw?"
Another flaw with the study, according to a comment published along with the study by Dr. Philip Sambrook, medical director of Osteoporosis Australia, is that the baseline vitamin D status is "largely unknown," since it was tested in only 60 of 5,292 people. "Because the patients were younger than in other studies, ambulatory and living in the community, they were less likely to have vitamin D deficiency" to start with, Sambrook noted.
"Overall, the data are still consistent with a therapeutic benefit of vitamin D on fractures in people deficient in vitamin D. But the effect ? in vitamin-D-replete individuals living in the community is less clear," Sambrook concluded.
The second study, published in the April 30 issue of BMJ (formerly British Medical Journal), found that women over age 70 who had one or more risk factors for fractures derived no benefit from supplementation with vitamin D and calcium. However, the researchers did not use placebo in the control group, which may have skewed results.
Retailers should tell consumers, "Don't stop taking your vitamin D and calcium supplements because of these studies," Shao said. "There's years and years worth of data showing there is evidence, lots of evidence, showing there [are] benefits."