Is Diet Cola Really Bad to the Bone?

Is Diet Cola Really Bad To The Bone?

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.

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  • Wonder if the 2006 study by Tucker et al controlled for the intake of calcium (and other minerals) from other sources, such as milk or mineral supplements? If not, it's not really that useful.

  • Mike:
    “We regressed each BMD measure on the frequency of soft drink consumption for men and women after adjustment for body mass index, height, age, energy intake, physical activity score, smoking, alcohol use, total calcium intake, total vitamin D intake, caffeine from noncola sources, season of measurement, and, for women, menopausal status and estrogen use.”

  • I don't understand why the author was so harsh on the first study. Anyone with half a brain the study was weak thus yielding an unreliable conclusion. The purpose was to present the paper to galvinize further research on the subject matter. Anyways, diet coke taste bad, imo, shouldn't be hard to kick

  • Reporting on a paper that was presented at a conference as a way to get funding for another study is really not very appropriate. This study is like a 4th graders science fair project, fun to do in 2 days of “work”. Just because the findings match other studies say nothing to their credibility.

  • You may consider not recommending lemon drinks, as this is even worse to the bones and teeth because of it's much more acidic properties than cola.

  • Hi, there,
    Interesting comment about the lemon. As it turns out, though, it’s not the acid in cola (or lemon) that is detrimental to the bones, but rather the phosphoric acid which is specifically found in dark-colored sodas. This is probably why non-cola sodas (like lemon sodas) have NOT been shown to have the same effect on bone as cola.

    As far as the teeth go, you may have a point! I suppose drinking from a straw would help to address that problem if someone absolutely had to have large amounts of lemon juice regularly.

  • Also the sodium benzoate or benzoic acid damage DNA.
    Drink water or green tea (no sugar) made in the coffee maker. One way to kick drinking cola is to drink sparkling water. It’s a little different at first, but it quenches thirst really well. All carbonation is supposedly hard on the teeth, but soda water is better than corn syrup or aspertame.

  • The calcium-phosphorus balance may be affected by the presence in nearly all colas of up to 3% phosphoric acid (as P2O5)? I’m in my 50’s and started avoiding Coke; now it’s so fizzy I just don’t like it, but I check now to see what acids are present. Phos acid is a very strong acid and strongly related to calcium.

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