Regular Cola Consumption Linked to Lower Bone Density in Women

September 22, 2003

Sept. 22, 2003 (Minneapolis) — Women who drink dark colas daily may have lower bone density than those who drink clear soda, according to findings of a study of women who were part of the Framingham Offspring Cohort.

While various studies have been done on soft drink consumption and bone health in children and adolescents, this study looked adults, said Katherine Tucker, PhD, associate professor of nutritional epidemiology at Tufts University.

In other studies, there has been an assumption that increased soft drink consumption meant lower intake of dairy and other calcium sources.

But in this cohort, "we looked at total calcium, and that was similar across the groups we studied. [Decreased bone density] wasn't because of lower calcium," she told Medscape in an interview. Dr. Tucker presented her findings here at the 25th annual meeting of the American Society for Bone and Mineral Research.

The problem appears to be increased levels of phosphoric acid, which can interfere with bone absorption. A typical can of cola contains 44 to 62 mg of phosphoric acid per 12 ounce serving, and diet cola contains 27 to 39 mg.

Data were presented on a total of 1,672 women and 1,148 men studied from 1996 to 2001. Bone mineral density (BMD) measurements were taken at the spine and three sites of the hip. The cohort was divided into two groups, those who consumed cola daily and those who drank cola (or other sorts of carbonated beverages including clear sodas) once a week or less.

The average daily phosphorus level of cola drinkers was 1,146 mg compared with 1,105 mg in nondaily cola drinkers, but this included all dietary sources.

Among the female subjects, regular cola drinkers had decreased BMD compared with the infrequent drinkers. BMD was 2.3% lower in the trochanter, 3.3% lower in the femoral neck, and 5.1% lower in Ward's area.

Yet, daily drinkers of cola had a slightly higher physical activity score and were similar to the infrequent cola drinks in all other respects.

"We've shown it was not due to lower calcium, it was not due to the caffeine in the cola, it was not due to the sugar, and we adjusted for calcium and vitamin D as well as body size. It seems the thing that's left is the phosphoric acid," Dr. Tucker said.

While phosphoric acid is present in other dietary sources, including dairy products, it may not cause the same sort of problem.

"When phosphoric acid comes packaged with other nutrients, it's absorbed normally and everything is in balance. We think the problem with cola is that you're getting those doses of phosphoric acid without any calcium. It's not balanced, and that extra phosphorus binds with calcium and prevents it from being absorbed," Dr. Tucker said.

This latest study still doesn't answer all the questions, said Dennis Black, PhD, professor of epidemiology and biostatistics at the University of California at San Francisco.

"This kind of study is hard because you ask people at one point in time 'what do you drink?' If you asked them a month earlier they may have drunk something different. It's very difficult to assess," he said.

The study also found that while cola consumption was associated with lower BMD in women, the same did not hold true for men.

Dr. Tucker reported no financial disclosures.

25th ASBMR: Abstract SU259. Presented Sept. 21, 2003.

Reviewed by Gary D. Vogin, MD

Pippa Wysong is a freelance writer for Medscape.


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