Consuming more calcium, either through dietary sources or through supplements, does not significantly increase bone density or prevent bone fractures in either men or women aged 50 and older, according to two new major review studies published Tuesday in The BMJ.
These new findings support the 2013 recommendation by the U.S. Preventive Services Task Force that older people not take daily calcium (or vitamin D) supplements to prevent bone fractures. That group of independent experts also said that the scientific evidence did not support such supplementation.
Despite the growing evidence against calcium supplementation, some groups continue to encourage older people to increase their consumption of the mineral. Perhaps the most visible of these groups is the National Osteoporosis Foundation (NOF), which recommends that women aged 51 to 70 and men aged 70 and older consume 1,200 milligrams (mg) of calcium and 800-1,000 international units (IUs) of vitamin D) daily — an amount few people can achieve without taking supplements.
Calcium supplementation is not without health risks, including serious ones. Clinical trials have found that taking calcium supplements at doses of 1,000 mg daily increases the risk of developing kidney stones and gastrointestinal problems severe enough to require hospitalization. Supplementation is also associated with an increased risk of heart attack and stroke.
In addition, recent research suggests that calcium supplements actually raise the risk of fracturing a hip.
No increase in bone density
Both of the new studies were conducted by the same team of researchers at the University of Auckland in New Zealand.
For one of the studies, the researchers analyzed data from 59 randomized controlled trials that had examined the effect of extra calcium intake, both from dietary sources and supplements, on bone mineral density in men and women aged 50 or older. (Randomized trials are considered the “gold standard” for this kind of research.)
The data revealed that increasing calcium intake — whether by taking supplements or by eating more milk, yogurt or other calcium-rich foods — improved bone mineral density by a meager 1-2 percent over five years.
Those “small effects … are unlikely to translate into clinically meaningful reductions in fractures,” the researchers conclude. “Therefore, for most individuals concerned about their bone density, increasing calcium intake is unlikely to be beneficial.”
No effect on fracture risk
In the second study, the scientists searched through all previous research on the effect of calcium intake on lowering the risk of bone fractures. They found too few randomized controlled trials to draw conclusions from, so they included observational studies in their analysis as well.
They discovered no association between dietary calcium intake and the risk of bone fractures. As for calcium supplementation, they found it appeared to have a small but inconsistent effect on reducing bone fractures — an effect, however, that was not enough to overcome the health risks associated with supplements.
Only one study, published in 1992, found a clear association between calcium supplementation and a reduced risk of bone fractures. But that study involved elderly women (mean age: 84) who lived in nursing homes. Those women were consuming very low levels of calcium and vitamin D in the nursing homes — and had very low concentrations of calcium in their blood.
Yet that study is often cited (without the specifics) by proponents of calcium supplementation as a reason why everybody needs to consume more of the mineral.
‘Follow the money’
“The evidence currently available … gives us a strong signal that calcium supplements with or without vitamin D do not protect older people in general from fractures,” writes Dr. Karl Michaelsson, a professor of surgical orthopedics at the University of Uppsala in Sweden, in a commentary that accompanies the two new studies in The BMJ.
That makes the continued emphasis on supplementation by organizations such as the National Osteoporosis Foundation “puzzling,” he adds.
Or maybe not so puzzling. As reported in an analysis published earlier this year (by two of the New Zealand researchers who worked on the new BMJ studies), many osteoporosis advocacy organizations around the world — including the National Osteoporosis Foundation here in the U.S. — receive substantial funding from supplement manufacturers and other nutrition-related companies.
“The profitability of the global supplements industry probably plays its part, encouraged by key opinion leaders from the academic and research communities,” writes Michaelsson. “Manufacturers have deep pockets, and there is a tendency for research efforts to follow the money (with accompanying academic prestige), rather than a path defined only by the needs of patients and the public. The research agenda and recommendations can also be influenced by the conflicts of interest that arise when leading academics have shares or management positions in companies making and marketing supplements.”