We’ve heard a lot of buzz about a small new study recently presented at the 2010 Endocrine Society conference which concluded that regular intake of diet cola was likely associated with loss of bone mineral density. So we decided to investigate further to see whether there was any truth behind the hype. The research, led by Dr. Noelle Larson, studied the levels of calcium in the urine of 16 women aged 18-40 who were assigned to drink either 24 ounces of water or diet cola on two separate days. They found that among the diet cola drinkers, there was a statistically significant increase in the amount of calcium present in the urine compared to the water drinkers. The researchers concluded that drinking diet cola produced a “negative calcium balance” in otherwise young, healthy women, that could contribute to lower bone mineral density (BMD) over time with chronic use. To be clear, the study itself was preliminary and pretty weak: it included only 16 women, followed them for only two days, compared diet cola to water (instead of diet cola to regular cola, or to non-cola sodas), and didn’t actually measure bone density–only the amount of calcium excreted in the urine. Additionally, it has not actually been published in a peer-reviewed journal; rather, it was presented as a paper at a conference. For all these reasons, no recommendations could responsibly be drawn on the basis of a study such as this alone. But just because the study itself is weak, doesn’t mean its conclusions are false. As a matter of fact, Larson’s study’s conclusions do validate the findings of previous, larger and better-designed studies which have suggested that cola-drinking of all kinds does negatively impact bone mineral density . For example, a 2006 study by Tucker and colleagues published in the American Journal of Clinical Nutrition measured actual bone density among 2,600 men and women whose average age was 58-59 years old. The researchers found that women, but not men, who drank cola of any type on a daily basis (diet or regular) had significantly lower bone mineral density (about 4-5% lower) in their hips compared to women who drank cola less than once per month. Furthermore, they found that regular intake of caffeine-free diet colas was less strongly associated with a reduction in bone mineral density– but still a statistically significant one compared to infrequent cola drinking. Finally, they found that non-cola carbonated beverages were not associated with any reduction in bone mineral density. The researchers suggested that the observed effect of diet and regular colas on bone mineral density compared to other carbonated beverages was likely due to the content of phosphoric acid in cola, and/or possibly some unidentified compounds present in cola extract. The bottom line is that these two studies contribute to a growing body of evidence that both regular and diet cola, far from being an innocent indulgence, appear to be more harmful than neutral, particularly for women and girls. If you’re addicted to the bubbly and just can’t seem to kick the habit, weaning yourself onto a non-cola carbonated soft drink would appear to be a marginally better choice from a bone-health perspective, according to the current research. Sparkling water with lemon or a splash of juice is preferable still, as it lacks the sugar, chemical sweeteners, caffeine and preservatives of a typical soft drink, all of which may contribute to sub-optimal health outcomes for the bones and beyond.