Protecting your bones isn’t just about drinking milk. It’s also about what you should NOT drink. And one of the biggest no-no’s for women may be cola.

Tufts University researchers found that women who regularly drink three or more servings of cola a day— regular OR diet— end up with lower bone mineral density in the hip. This can lead to osteoporosis— a progressive disease that makes bones thinner, brittle and more breakable.

The study tracked about twenty-five-hundred women and men. The women drank an average of five carbonated drinks a week, including four colas. And the men drank six soft drinks a week, five of them colas.

Lower bone density was NOT seen in men or women who regularly drank non-cola soft drinks. And decaffeinated colas were not as harmful either. But researchers say caffeine isn’t the issue. Cola is.

The researchers looked at several factors… vitamin D and calcium intake, physical activity and how many vegetables and fruits the women ate. But none explained the findings.

Previous studies linked bone loss to cola-drinking, but doctors figured this was because cola drinkers drink less milk. That wasn’t the case in the Tufts study, which found that women who regularly drink colas had overall lower calcium intake, probably because they eat less.

Some researchers think phosphoric acid in cola is the culprit. Others doubt the link between cola-drinking and bone loss altogether. But both urge women to watch cola intake and eat plenty of low-fat dairy foods, fruits and vegetables.