Since bones tend to deteriorate with age, it makes sense to take in more calcium as we get older, to help lower the risk of fractures in our hips and limbs. But how much additional calcium is enough? And is there such as thing as too much?
Yes, says Eva Warensjo, a researcher at Uppsala University in Sweden, who reports this week in the British Medical Journal that excessive calcium may actually cause, rather than prevent fractures. The Swedish team analyzed data from more than 60,000 women born between 1914 and 1948 and tracked their calcium intake and fracture rates over a period of 19 years. The women answered questionnaires about how much calcium they consumed both through their diet — from dairy products such as yogurt, milk and cheese and from leafy green vegetables — and through calcium supplements.
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The women consuming the least amount of calcium (less than 750 mg) each day increased their risk of having a first fracture by 18%, compared with those getting about 900 mg each day, which is close to the amount recommended by Swedish health officials. Women who took in more calcium, up to 1,140 mg daily, saw little additional benefit in lowering their risk of fractures.
The data suggest that current U.S. recommendations for calcium intake — at least 1,200 mg daily for women over age 50 to prevent fractures — may be too high. The guidelines represent the best available data linking calcium to bone health and reduced fracture risk, particularly in postmenopausal women, who are less able to build enough bone to keep up with skeletal deterioration. But scientists have been debating how valid this advice may be, since baseline levels of calcium at menopause tend to vary widely depending on women’s ethnic backgrounds, socioeconomic status and lifestyle.
Some women may need more calcium, especially if they smoke, which can weaken bone. Others who are physically active may need less; calcium, after all, is only one of a variety of factors that contribute to bone health — exercise, particularly weight-bearing activities, can build bone quite effectively.
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“According to our study, yes, the U.S. recommendations might be set too high,” says Warensjo. “I think we will need more data to really confirm if this is correct, but we would say that based on these results of this study, it’s probably not necessary to go that high in order to have an adequate intake of calcium to prevent osteoporotic fractures.”
Still that doesn’t necessarily mean that women who supplement their diets with calcium pills are wasting their time. Dr. Julie Switzer, a member of the American Academy of Orthopedic Surgeons’ Women’s Health Issues Advisory Board, says the findings also suggest that too little calcium can increase fracture risk. For women who may not be getting enough, increasing their dietary intake or supplementing with calcium can help lower their chances of breaking a bone.
There’s a limit to the benefit, however. Overconsumption of calcium may be detrimental, actually promoting, rather than preventing bone fractures, the study found, since excessive amounts of the mineral may shut down bone construction sites in the skeleton.
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Warensjo and her team highlight the tipping point — or tipping range — beyond which calcium appears to stop adding to bone health. That range, Warensjo says, seems to be somewhere around 700 mg to 800 mg of calcium a day. It’s all about balance, she says.
As for the current U.S. dietary guidelines, health officials may be revisiting their advice soon. “This may be opening the door to modifying our recommendations for calcium intake,” says Switzer.