Periodical Soda Pop and Weakened Bones: How are They Linked?


Scientists have seen an association for some time between consumption of soda pop and a risk for weakened bones, but they haven't been certain why. One hypothesis has been that the phosphorus in carbonated beverages, particularly in colas, contributes to calcium loss from bones. The reasoning has been based on the idea that phosphorus (usually listed on soda bottles as phosphoric acid) binds to calcium in the gut, thereby preventing the calcium from being absorbed and making its way to bone.

Another theory is that calcium and phosphorus need to be eaten in a particular ratio to maintain bone health. Presumably, a lot of phosphorus without any calcium whatsoever-the makeup of soda pop-could throw off the delicate calcium/phosphorus balance.

But a new study, conducted by researchers at Omaha's Creighton University Osteoporosis Research Center, suggests the mechanism is much simpler: Too many carbonated beverages, now the preferred thirst quencher among many people, simply replace calcium-rich milk in the diet. It's not a new hypothesis; nutritionists have been lamenting a wrong-way shift in the soda/milk see-saw for years. But the study helps strengthen the argument.

In a carefully controlled experiment, the researchers gave a group of several dozen women different soda pops on different days, some containing phosphorus (such as Coke), and some without it (like Mountain Dew and Sprite). The women excreted no more calcium in their urine after drinking the phosphorus-containing beverages than the other ones, so it did not appear that phosphorus was hindering uptake of calcium by the gut and then sending it out of the body. The only thing that made a difference was the caffeine in some of the soda brands, which caused extra calcium excretion. But even that was made up for with reduced calcium in the urine later in the day.

The bottom line, the researchers say, is that the adverse effect of carbonated beverages on bone health "lies not in what these beverages contain, but in what they do not: the needed nutrients for bone health."

Other mineral researchers concur. "Milk displacement is responsible for significant declines in the amount of calcium Americans are consuming today, which is a far greater threat to bone density than the amount of phosphorus in a can of soda," says Bess Dawson-Hughes, MD, chief of the Calcium and Bone Metabolism Laboratory at Tufts. Adds James Fleet, PhD, of Purdue University's Department of Foods and Nutrition, "milk is a vital source not only of calcium but also of vitamin D. Drinking a limited amount of soda is not detrimental to your bones, but milk and other calcium-rich foods have to remain daily staples."

Share this with your friends