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Q.I've heard that club soda, seltzer water, and sparkling mineral water rob the bones of calcium. Is it true?
IN.Warnings appear from time to time about the harmful effects of carbonated drinks on the bones. The theory is that the phosphoric acid (phosphate), used to improve the taste of some carbonated drinks, can interfere with calcium absorption and result in the loss of calcium from the bones. Fortunately, there is no good evidence that high phosphate intake affects bone metabolism or bone density.
Yet carbonated drinks have long been linked to low bone density and bone fractures in adolescent girls. To investigate this association in adults, researchers at Tufts University examined data from 2,500 women and men (ages 49 to 69) involved in the Framingham Osteoporosis Study. They assessed dietary intake and measured bone mineral density (BMD) at the spine and hip.
Carbonated drinks without cola were not associated with low BMD, but cola intake was associated with lower BMD at the hip (but not the spine) in women, but not in men. The more cola a woman drank, the lower her BMD. Women who drank more cola did not drink less milk, but did have a lower calcium intake.
In 2005, theBritish food magazinepublished the results of a small clinical trial that compared healthy postmenopausal women who drank about one liter of non-carbonated mineral water daily with those who drank the same amount of carbonated mineral water. After eight weeks, blood and urine tests for bone turnover showed no difference between the two groups.
It appears that drinking seltzer water does not contribute to osteoporosis or increase the risk of fractures in women. The authors of the cola study suggested that the caffeine in cola could be the cause of cola drinkers' lower BMD. Other studies have also reported a link between caffeine and lower BMD. In some cases, soft drinks replace calcium-rich drinks such as milk, and experts believe that this, rather than a direct effect of soft drinks on bones, may explain the effect on BMD in adolescent girls.
So feel free to enjoy seltzer without worry, but don't overdo the caffeinated drinks, whether they're carbonated or not. And if you suspect that drinking seltzer water, coffee, cola, or other soft drinks may help you reduce your intake of healthy beverages, such as calcium- and vitamin D-fortified juice and milk. So make sure you get enough calcium from other dietary sources and consider a daily vitamin D supplement.
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