More than half of all Americans, mostly women , are at risk of osteoporosis, a disease that makes bones brittle and prone to fracture. Now a Tufts University study  involving 2500 men and women shows a link between cola drinking and bone loss.

Lead author Katherine Tucker says the more cola consumed, the greater the loss in bone density. "The bone mineral density of women who were drinking cola daily was about three to five percent lower than the bone mineral density of women who were only drinking cola occasionally."

Tucker says this is a significant amount in nutritional terms and translates into increased risk of fracture. Tucker says women who had an occasional cola did not suffer bone loss. Nor did men, no matter how much cola they drank. "We think that is probably because men have denser bones to begin with and have a larger blood volume on average," she says. "We know that women are at greater risk than men of osteoporosis in general and probably more sensitive to these shifts in acidity."

Tucker says it is that acid - specifically phosphoric acid - that is of particular concern in cola. "Phosphoric acid is an acidic ingredient that will lead to some acidification of the blood. And when the blood is acidified it needs to balance the ph level and so can take calcium out of the bone to do that."

Seventy percent of study participants consumed cola over other carbonated beverages.

Tucker says while more research needs to be done, the study recommends that women at risk of osteoporosis substitute a healthier beverage for cola in their diet.

The study was published in the American Journal of Clinical Nutrition.