For years, many people have taken calcium and vitamin D supplements to help keep their bones strong as they age. Walk into any pharmacy or supermarket and you’ll find shelves full of products promising to support bone health, prevent fractures and reduce the risk of falls.

Calcium is an important building block of bone, while vitamin D helps the body absorb calcium. If weak bones increase the risk of fractures, surely taking more calcium and vitamin D should help keep bones strong. But a major new study suggests the reality may be far more uncertain.

Researchers analysed data from 69 clinical trials involving more than 154,000 adults from around the world. These studies compared calcium supplements, vitamin D supplements, or a combination of both against a placebo or no treatment. The aim was to answer a question that has important implications for millions of people: do these supplements actually prevent fractures and falls?

When researchers looked at calcium alone, they found little or no meaningful reduction in fractures or falls. The same was true for vitamin D taken on its own. Even among........

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