LONDON (MarketWatch) — Women who regularly drink cola could be increasing their risk of osteoporosis, U.S. researchers say, the BBC reports on its Web site Friday.

Their study of 2,500 people revealed drinking cola was linked with low bone mineral density in women regardless of their age or calcium intake. But the work published in the American Journal of Clinical Nutrition found no such link in men.

Katherine Tucker, director of the Epidemiology and Dietary Assessment Program at Tufts University in Boston, and colleagues compared information from dietary questionnaires with bone mineral density measurements at the spine and three different hip sites.

Men reported drinking an average of five cola drinks a week, and women reported consuming four cola drinks a week.

Cola consumption was linked to lower bone mineral density in all three hip sites in women, although not in the spine, but was not associated with bone mineral density in men.

There was no association with bone mineral density loss for women with other carbonated drinks, however.

Past work suggests that consumption of cola may be detrimental to bone health because it replaces milk in the diet, but in the current study the women who drank higher amounts of cola didn't drink less milk than others.

However, calcium intake from all sources, including non-dairy sources such as dark leafy greens or beans, was lower for women who drank the most cola.

An ingredient of cola called phosphoric acid might be responsible for the link, but the mechanism is not fully understood.

Tucker said: "We think that particularly in doses in cola and especially when it's repeated daily, phosphoric acid creates an acidic environment in the blood. Calcium is then taken out of the bones to balance that out. But that view is controversial."

She advised: "Women, particularly those concerned about osteoporosis, should limit their intake of cola to occasional."