Increasing intake of calcium - found in dairy products such as milk and cheese - does not improve the bone health of older adults, new research finds.
Around 99% of the body's calcium is stored in the teeth and bones, where it helps support their function and structure. The remaining 1% aids muscle function, nerve communication, hormone secretion and blood vessel movement.
In the US, it is recommended that men ages 51-70 get around 1,000 milligrams of calcium from their diet each day, while the recommended daily calcium intake for women of the same age is around 1,200 mg. For men and women aged 71 and older, the daily recommended calcium intake is 1,200 mg.
Dairy products such as milk, yogurt and cheese are the most common natural sources of calcium, though the mineral is also found in nondairy products, including sardines, kale and broccoli.
According to study author Mark J. Bolland, associate professor in the Department of Medicine at the University of Auckland in New Zealand, and colleagues, the average daily calcium intake among older adults in Western countries is only around 700-900 mg.
As such, many older individuals turn to calcium supplements in order to boost their intake to meet dietary recommendations, encouraged by claims that increasing calcium intake may improve bone density and reduce the risk of fractures.
In the two new studies, however, Bolland and colleagues find this is unlikely to be the case.
Calcium intake guidelines for older adults 'should be reconsidered'
For both studies, the team conducted a review of observational studies and randomized controlled trials that looked at how increased intake of dietary or supplemental calcium impacted bone density and fracture risk among men and women aged 50 and older.
- Postmenopausal women, vegetarians and people who are lactose intolerant are just some groups at risk for calcium deficiency.
- Too much calcium - known as hypercalcemia - can lead to constipation and kidney stones
- A plain, 8-oz low-fat yogurt makes up around 42% of an adult's daily recommended calcium intake.
In the study assessing calcium intake and bone density, the researchers identified 59 eligible randomized controlled trials.
They found that men and women who increased their calcium intake through either dietary or supplementary sources experienced a 1-2% increase in bone mineral density, which the team says is "unlikely to lead to a clinically significant reduction in risk of fracture."
The second study involved 44 cohort studies and two randomized controlled trials that assessed the link between increased calcium intake from supplements, milk and dairy and other dietary sources.
From this analysis, the team concluded that dietary calcium intake is not linked with reduced risk of fracture among older adults, and that there is no evidence from clinical trials that increasing calcium intake from dietary sources prevents fractures. "Evidence that calcium supplements prevent fractures is weak and inconsistent," they add.
In an editorial linked to the studies, Prof. Karl Michaëlsson, of the Department of Surgical Sciences at Uppsala University in Sweden, notes that, given the lack of evidence that increasing calcium intake improves the bone health of older adults, current recommendations are "puzzling."
Prof. Michaëlsson points out that if older adults follow current guidelines for daily calcium intake, they may even be putting their health at risk:
"Most will not benefit from increasing their [calcium] 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.
The weight of evidence against such mass medication of older people is now compelling, and it is surely time to reconsider these controversial recommendations."
While increasing calcium intake may not improve bone health in seniors, a study reported by Medical News Today in 2013 suggests a calcium-rich diet may prolong lifespan for women.