A meta-analysis newly published in JAMA (2017;318(24):2466-2482) found no association between vitamin D and calcium supplementation and risk of fracture in older adults. However, the Council for Responsible Nutrition (CRN) highlighted several limitations of the otherwise sound meta-analysis and reminded most Americans do not get enough of these essential nutrients that impact critical body functions including bone health.
The JAMA reviewers looked at 33 randomized clinical trials involving 51,145 participants and the impact of either calcium, vitamin D, or combined calcium or vitamin D supplements on incidence of fracture in adults aged 50 years and older. They found no significant differences between any of the supplement groups compared to placebo or no treatment. The reviewers thus concluded the results “do not support the routine use of these supplements in community-dwelling older people."
Several nutrition industry groups said this study is not the final word and urged people to think twice about stopping supplementation based on this study alone.
Daniel Fabricant, Ph.D., president and CEO of the Natural Products Association (NPA), said the study draws its conclusions with too broad of a brush and has many flaws, including its focus only on the healthiest segment of the population, which are those living at home.
“It likely includes many people who may be getting—and benefitting from—calcium and vitamin D from their diet or other sources," he explained. “And people who live in nursing homes or assisted living facilities were not part of it, which means there is a lot missing." He advised people with prior bone breaks or family incidence of osteoporosis may still need vitamin D and calcium supplementation, other nutrition. “We will look more closely at this study in the coming days, but the bottom line is that people should continue taking vitamin D and calcium as their doctors tell them to," he said.
Andrea Wong, Ph.D., vice president, scientific & regulatory affairs for the Council for Responsible Nutrition (CRN), agreed the study had limitations and said all Americans, specifically older adults, have a basic need for calcium and for vitamin D, as both are essential nutrients and are necessary for a host of critical functions in the body, including building strong bones. She noted government research has shown Americans do not get enough of either calcium or vitamin D.
“In fact, the current Dietary Guidelines for Americans identify both calcium and vitamin D as shortfall nutrients of public health concern," she said. “For older adults, specifically, we know that getting enough nutrients can be problematic, so dietary supplements become even more important—not as a replacement for food—but as an addition to a diet that should be rich in calcium-containing foods such as milk, cheese, and spinach, as examples." She further reminded that people find it even more difficult to get enough vitamin D from food because few foods are rich in vitamin D. “Generalized recommendations relying on this study should be mindful that further reductions in calcium and vitamin D consumption may exacerbate these public health concerns," she said.
Wong pointed out the study authors noted four limitations, including their acknowledgement that “Some trials included in the analysis didn’t test baseline vitamin D blood concentration for all participants; the results for some subgroups might have been different if all individuals were tested." She said that without knowing the blood levels of subjects before they began the intervention, one can’t assess whether the individuals were deficient in the first place.
“Another significant limitation not acknowledged by the authors involves the inclusion of the Women’s Health Initiative (WHI), a study which included a particularly large number of subjects, and consequently heavily weights the meta-analysis," Wong noted. “Unfortunately, the WHI data has been widely acknowledged as having limitations of its own having to do with subjects not taking the supplements as directed by the protocol, as well as those who took calcium and vitamin D supplements on their own (outside the protocol) before and during the study."
Wong reported a subsequent re-analysis of the WHI data demonstrated a reduced risk of hip fractures in subjects receiving calcium and vitamin D who did not take personal calcium or vitamin D supplements at baseline. Further, another meta-analysis using the WHI re-analysis also showed that calcium plus vitamin D supplementation significantly reduced risk of total fractures and hip fractures in middle-aged to older adults.
“CRN recommends that people discuss their individual needs for calcium and vitamin D with their healthcare practitioners," she advised. “If there is the possibility of reducing the risk of a devastating fracture by supplementing with calcium and vitamin D, as some research has found, people should not be dissuaded from supplementation by a meta-analysis that is meant as a general recommendation, and may not apply to each individual."