THURSDAY, Aug. 23, 2001 (HealthDayNews) -- Remember all that scientific noise about soft drinks being bad for bone health, particularly in women? Well, score one for the junk food brigade: A new study shows that bubbly beverages won't hurt your bones -- unless you drink so much that they take the place of other calcium-rich foods or beverages.
"It seems that the only way soda is going to harm the health of your bones is if you choose this beverage over a calcium-rich beverage, such as a fortified juice or a glass of milk," says study author Dr. Robert Heaney, a professor of medicine at Creighton University School of Medicine, in Omaha, Neb., where the research was conducted.
But before you throw coins in that vending machine, consider this: Experts also say women aren't getting enough calcium-rich foods, and part of the reason may actually be because they fill up on the carbonated beverages.
"Drinking soda, in and of itself, may not harm you. But when you consume soft drinks to the exclusion of other foods and beverages that do contain calcium, then yes, soda can represent a threat to a woman's health," says New York University Medical Center nutritionist Barrie Wolfe.
The whole idea that soda might harm your bones was born from the theory that too much phosphorus could leech calcium from the body, thus increasing the risk of fracture. Because phosphorus is plentiful in many soft drink formulas, the connection between soda and weak bones was made.
There was never any scientific proof that this was, indeed, the case. But as the soft drink industry continued to blossom -- soda is now considered the No. 1 beverage of women between 20 and 40 years old -- researchers began to take the pseudo-scientific theories under greater scrutiny.
"We just got tired of everyone assuming that soda was bad for bone health without ever having any real proof one way or the other, and that's why we decided to do the study," Heaney says.
The research -- just published in the American Journal of Clinical Nutrition -- involved 32 women, all of whom confessed to gulping down at least 24 ounces of soda a day.
In order to test not only the effects of phosphorus-laden sodas, but also other components of soft drinks, four different formulations were tested: Coke (containing caffeine and phosphorus), Coke-free (no caffeine but with phosphorus ), Mountain Dew (caffeine and citric acid, no phosphorus) and Sprite (no caffeine, no phosphorus but with citric acid).
To help ensure that the consumption of liquid alone wouldn't yield any specific results, plain water was used as a "negative" control, while skim or chocolate milk was a "positive" control.
The women were told to fast overnight, urinate upon rising, skip breakfast and report to the clinic, where they remained for two more hours without food. A urine sample was then collected (to check levels of calcium, creatinine, sodium and acid) and after that, the women were then given a light breakfast consisting of the test beverage, and low-calcium Italian bread with butter. The beverage serving sizes were 20 ounces for the soda or water, and 12 ounces for the milk. To up the difference in fluid consumption, the milk drinkers were also asked to consume an additional 8 ounces of water with their meal.
To equalize carbohydrate and sugar intake, some of the women were given jelly beans along with their meal.
For five hours after that, all the women drank about 20 ounces of water. At the five-hour mark, another urine sample was collected.
In addition, a kind of "musical chairs" random block selection was used so that by the time the study ended -- a period of about one month -- each of the women had sampled five of the beverages -- one water, two colas, one milk, and one citric acid soda.
The result: Urine tests showed an excess of calcium was excreted in only two groups -- those who drank the milk (an expected result) and those who drank the caffeine-rich sodas -- although the amount was so small it was not considered significant.
In addition, previous studies showed the calcium-robbing effects of caffeine beverages in general are compensated for by the body.
"Essentially, the body makes up for the loss of calcium induced by the caffeine, by holding on to more calcium later in the day," says Heaney.
The phosphoric acid component of the sodas -- the suspected culprit -- had no effect on calcium excretion.
"The theory that soda is bad for bone health was finally proven not true -- unless, as I said before, drinking soda keeps a woman from drinking calcium-rich beverages such as milk," says Heaney.
The study, which was partially funded by a prominent dairy organization, did not prove that soda drinkers choose carbonated beverages over milk, or that they would drink more milk if soda wasn't available.
According to Wolfe, however, the study did show that choosing a low-fat dairy drink -- like skim milk, a fat-free yogurt shake or a calcium-fortified juice -- over soda is the better way to go.
"Soda may not harm your bone health, but it certainly doesn't help it -- while a calcium-rich beverage can satisfy your thirst and help your bones at the same time," says Wolfe. She believes women don't get enough calcium because they do fill up on soda.
Heaney says it's possible to have your Coke and your calcium too: "Just don't drink soda to the exclusion of calcium-rich foods and beverages and you'll be all right," he says.
What To Do
To find good sources of calcium-rich foods, click here.
To learn how to incorporate more calcium into your diet, without dairy products, click here.
To find out how calcium supplements can help, click here.
The U.S. Department of Agriculture has an excellent nutrition analysis tool on its site.
