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You Can't Bone Up on Colas—Osteoporosis Study
By Russell H. Greenfield, MD, Dr. Greenfield is Clinical Assistant Professor, School of Medicine, University of North Carolina, Chapel Hill, NC, and Visiting Assistant Professor, University of Arizona, College of Medicine, Tucson, AZ; he reports no consultant, stockholder, speaker's bureau, research, or other financial relationships with companies having ties to this field of study.
Source: Tucker KL, et al. Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The Framingham Osteoporosis Study. Am J Clin Nutr 2006;84:936-942.
Abstract: Subjects were drawn from a large population-based cohort (the Framingham Offspring Cohort) to determine whether regular carbonated beverage consumption, including both cola and non-cola types, is associated with lowered bone mineral density (BMD) in men and pre- and post-menopausal women. BMD was measured at the spine and three hip sites in 1,413 women and 1,125 men using dual-energy X-ray absorptiometry. Diet was assessed using a validated, semiquantitative food-frequency questionnaire. Each BMD measure was regressed on the frequency of soft drink consumption after adjustment for a number of potential confounding factors (including body mass index, height, age, energy intake, physical activity score, smoking, alcohol use, total calcium intake, total vitamin D intake, caffeine from non-cola sources, and, for women, menopausal status and estrogen use). Participants were found to be generally overweight, former smokers, and moderate users of alcohol. More than three-quarters of the women in the study were postmenopausal, of whom 29% were using estrogen.
No significant association between non-cola carbonated beverage intake and BMD was observed for either gender. In men, no significant association was found between cola intake and BMD. Cola intake was, however, associated with a significantly lower BMD at each hip site, but not the spine, in women after adjustment for potential confounding factors. Similar results were seen for diet cola, and a weaker association identified with decaffeinated cola. For women, greater intake of cola was not associated with a significantly lower intake of milk, but was associated with a lower intake of dietary calcium. Total daily phosphorous intake was not significantly higher in daily cola consumers than in non-consumers. The authors conclude that regular intake of any type of cola drink, but not of other carbonated soft drinks, is associated with lower BMD in women.
Previous studies in adolescent girls have raised the specter of carbonated drinks having a negative impact on fracture rates, perhaps by displacing healthier beverages (including sources of calcium, like milk) from the diet. As the authors of this study rightly point out, little attention had been paid to the potential impact of carbonated beverages on bone health in adults.
Colas often contain both caffeine (increases calcium excretion) and phosphoric acid (interferes with calcium absorption), both of which might adversely affect bone health. Results of this study suggest the negative effect of cola on BMD appears stronger with caffeinated forms; however, a significant, albeit weaker, negative effect was found with decaffeinated cola intake as well, essentially negating the possibility that caffeine alone explains the harmful effects of regular cola ingestion. The findings are striking for the fact that risk was identified only in women, and that risk was associated with relatively conservative cola intakes: women who enjoyed three or more servings of cola per week had an increased risk of lowered BMD compared to those who enjoyed less than one cola per week. With an aging population and increasing lifetime fracture rates in both women and men, identification of modifiable risk factors that can easily be acted upon takes on supreme importance. At present, it appears that counseling women to lessen their intake of carbonated colas would be prudent.