Researchers question current daily intake recommendations

09.30.2015
by Jeff Minerd
Contributing Writer, MedPage Today

Increasing one’s calcium intake, whether from dietary sources or supplements, does little to improve bone health or prevent fractures in older adults, according to a pair of systematic reviews published in the The BMJ.

Given these findings, calcium supplementation should not be recommended for fracture prevention in older adults, concluded a research team led by Mark Bolland, MD, of the University of Auckland in New Zealand.

Organizations including the Institute of Medicine(IOM) and National Osteoporosis Foundation (NOF) recommend 1,200 mg of calcium daily for women 50 and older. However, the average dietary intake in Western countries is 700-900 mg/day, meaning that most women need to take calcium supplements to meet those recommendations, Bolland and colleagues said.

“In some Western countries, more than 30-50% of older women take calcium supplements,” they said.

However, calcium supplements have been associated with adverse events including cardiovascular events, kidney stones, and hospital admissions for acute gastrointestinal symptoms. Consequently, older adults have been encouraged to boost their calcium intake through food rather than supplements, the researchers said.

“We assessed the evidence supporting the recommendation to increase dietary calcium intake to prevent fractures and compared the anti-fracture efficacy of increasing calcium intake through dietary sources with the anti-fracture efficacy of calcium supplements,” they said.

The first systematic review included 59 randomized controlled trials of dietary calcium or supplements in adults 50 and older, with bone mineral density (BMD) as the main outcome.

Increasing calcium intake from dietary sources increased BMD by 0.6-1.8%. Calcium supplements increased BMD by 0.7-1.8%. These increases were achieved at one year, with no further increases in subsequent years.

“Increases in BMD of about 1-2% over one to five years are unlikely to translate into clinically meaningful reductions in fractures,” the investigators wrote.

The second systematic review included randomized trials and observational studies of calcium intake in adults 50 and older with fracture as the main endpoint. There were 52 such studies evaluating dietary calcium and 26 studies evaluating calcium supplements.

For dietary calcium, no association was found between calcium intake and fracture risk. For calcium supplements, risk of fracture was reduced by 11% (RR 0.89; 95% CI 0.81-0.96) in pooled data.

However, many of the studies showed no effect on fracture risk, and only one study — of frail elderly women in residential care with low dietary calcium intake — showed significant reductions in fracture risk.

“Evidence that calcium supplements prevent fracture is weak and inconsistent,” the researchers concluded.

“Collectively, these results suggest that clinicians, advocacy organizations, and health policy makers should not recommend increasing calcium intake for fracture prevention, either with calcium supplements or through dietary sources,” they said.

Karl Michaëlsson, MD, PhD, of Uppsala University in Sweden, agreed in an accompanying editorial.

“As there is currently little, if any, firm evidence that higher intakes prevent bone loss, falls, or fractures in middle aged or older women and men living in the community, the continued emphasis by several organizations (such as NOF) on ever increasing intakes of calcium and vitamin D is puzzling,” Michaëlsson wrote.

“Most will not benefit from increasing their intakes and will be exposed instead to a higher risk of adverse events such as constipation, cardiovascular events, kidney stones, or admission for acute gastrointestinal symptoms,” he said.

“The weight of evidence against such mass medication of older people is now compelling, and it is surely time to reconsider these controversial recommendations,” he said.

The NOF and the IOM declined to provide spokespeople to comment on this story.

The National Institutes of Health Office of Dietary Supplements also declined to comment on the studies, referring instead to their Calcium Dietary Supplements Fact Sheet, which repeats the recommendation of 1,200 mg/day total calcium from diet or supplements for women older than 50 and men older than 70. It also indicates that intake up to 2,000 mg/day in older adults is considered tolerable.

• Reviewed by F. Perry Wilson, MD, MSCEAssistant Professor, Section of Nephrology, Yale School of Medicine and Dorothy Caputo, MA, BSN, RN, Nurse Planner

LAST UPDATED 10.01.2015