Forget everything you've been told about calcium - increasing your intake is unlikely to improve bone health.

Research by a New Zealand professor on how calcium affects bone density is being published in The British Medical Journal today.

The research seeks to compare the effects of increased intakes from calcium supplements to intakes from foods.

University of Auckland Associate Professor and study author Mark Bolland said the study revealed eating more food or taking supplements doesn't make bones stronger.

He says what they found was that taking supplements was unlikely to prevent fractures - only one variation was observed - and there was no evidence at all that increasing food intake prevented fractures.

In fact, he warns there's a small chance serious side-effects can occur such as kidney stones, heart attacks and possibly strokes.

Bolland adds it's not the first study to show this, it was proven 15 years ago but the public are taking some time to catch on.

"I think that many people still believe increasing calcium intake will prevent fractures because those are the messages that they've received from people that write guidelines and osteoporosis advocacy groups."