While enjoying a cola or two every day might seem harmless enough, recent research suggests that those tasty drinks could be compromising your bone health.

"There is enough evidence that high consumption of soda and carbonated beverages is associated with somewhat lower bone mass in children, and that's a real concern and people should be aware of it," said Dr. Lawrence Raisz, director of the University of Connecticut Center for Osteoporosis.

The exact mechanism behind the problem isn't clear, but experts believe that drinking soda -- particularly colas -- affects bone density in several ways. One reason may be that people who drink colas are simply less likely to get enough calcium and vitamin D in their diets, because the soda is replacing more nutritious beverages, such as milk or calcium-fortified juice.

Or, it could be related to the caffeine in colas, because caffeine has been linked to a higher risk of osteoporosis.

The third possible explanation focuses on one of the ingredients found in colas: phosphoric acid. Phosphoric acid can cause an imbalance in the body as the body seeks to neutralize the acid with calcium. If there isn't enough calcium in the diet, the body will take calcium from the bones.

"Phosphate is in milk, but milk also contains calcium and vitamin D. In soft drinks, there is just phosphoric acid and no calcium. Extra overzealous drinking may lead to a phosphoric acid imbalance, and if there's not enough calcium, the body goes to the bones to restore the balance," explained Dr. Primal Kaur, director of the Osteoporosis Center at Temple University Health Sciences Center in Philadelphia.

Low levels of calcium are associated with the development of osteoporosis, a disease that thins the bones so much that they're at risk of fracture. More than half of Americans, especially postmenopausal women, have an increased risk of developing osteoporosis, according to the National Osteoporosis Foundation.

In a study that included more than 2,500 people with an average age of about 60, researchers from Tufts University found that cola consumption by women was associated with lower bone mineral density at three hip sites, regardless of age, menopause, total calcium and vitamin D intake. The women reported drinking an average of five carbonated drinks a week, four of which were colas.

There was less of a problem with decaffeinated cola, but the findings were similar for diet soft drinks. The researchers didn't find an association between cola drinking and lower bone mass in men.

Results of the study were published recently in theAmerican Journal of Clinical Nutrition.

"Moderation is really important. If you really like soft drinks, you don't need to take them out of your diet completely, but limit yourself to one or two glasses" a week, Kaur said.

And, she added, make sure you're getting enough calcium and vitamin D to protect your bone health. Vitamin D needs vary by age, and where you live, so check with your doctor to find out how much vitamin D you should be consuming each day. Kaur said that if you're not getting at least 1,000 to 1,200 milligrams of calcium daily from your diet, you should take a calcium supplement to ensure you're getting adequate amounts of the mineral.

Another important way to prevent osteoporosis, according to Raisz, is to exercise.

"The standard recommendation is a half an hour a day for adults and an hour a day for kids, butanythingis better than nothing," he said. "Try to walk at least a half a mile a day, and engage in a weight-bearing exercise of some sort."

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