Increasing calcium intake through diet or supplements shouldn't be recommended to prevent fractures, say researchers who reviewed studies on the link between calcium and bone health.

Researchers in New Zealand analyzed more than 100 published studies on taking calcium in food or pills to strengthen bones or to prevent fractures.

"Taken together, we think this is the strongest possible evidence that taking calcium supplements will not be beneficial unless there are clear medical reasons that a calcium supplement is needed," said Mark Bolland, an associate professor in the department of medicine at the University of Auckland.

Sue Williams, 25, climbs a rock wall as a weight-bearing exercise to maintain bone density and build muscle mass. (Aaron Harris/Canadian Press)

Bolland led one study review, and was a member of the second study review, published in BMJ.

One review focused on two dietary studies that compared how patients over 50 years of age fared when asked to eat higher compared with lower levels of calcium.

The research team also looked at 44 studies on how long-term intake from food or supplements affected fracture risk.

The conclusion: None of the research provided any evidence that calcium intake is associated with fracture risk.

The second review focused on 59 studies that looked at the effect of calcium from either food or supplements on bone mineral density in people aged 50 and older.

In that study, boosting calcium intake in whatever form was associated with a small uptick in bone mineral density. But the researchers concluded that the 1 to 2 per cent increase detected are unlikely to translate into reduced fractures.

"For most individuals concerned about their bone density, increasing calcium intake is unlikely to be beneficial."

Dr. Andrew Grey is an endocrinologist at the University of Auckland in New Zealand. He wrote a journal commentary in July. The widespread belief and recommendation that people should take a certain of dietary calcium to improve bone health is wrong, Grey said.

"It's superficially attractive because there's calcium in bones," Grey said in an interview. "That doesn't mean taking in calcium strengthens the bones."

Doctors note too much calcium increases the risk of kidney stones and possibly heart attacks.

The research should not be interpreted to mean calcium has no benefit, cautioned Dr. Sandra Kim of Osteoporosis Canada in Toronto.

"The studies really all together have been inconsistent and the association is weak," Kim said.

"That's why Osteoperosis Canada recommends that calcium intake is preferable from dietary sources and to only use supplements if this is not possible."

Currently, the recommeded daily intake calcium intake is between 1,000 and 1,200 milligrams per day.

Other ways to keep bones strong as you age include:

Eat a balanced diet and maintain a healthy weight.

Stop smoking.

Exercise regularly including balance and strength work outs to reduce your risk of a debilitating fall.

The research was funded by the Health Research Council of New Zealand.