By Salynn Boyles
WebMD Health News 2006. © 2006 WebMD Inc.

Oct. 6, 2006

Women who are concerned about thinning bones may want to limit the number of colas they drink.

Researchers found that drinking cola soft drinks on a regular basis was associated with lower bone mineral density in the hip.

Lower bone density can lead to osteoporosis, which, in turn, can cause bone fractures. Complications from hip fractures are a common cause of disability — and even death — in women as they age.

The association was not seen in men, and it was not seen in women who regularly drank noncola soft drinks.

Drinking three or more cola soft drinks a day was associated with lower bone density. Results were similar for diet colas. However, the potentially harmful effect was less for decaffeinated cola.

“Caffeine may explain part of this, but it doesn’t explain it all,” researcher Katherine L. Tucker, PhD, of Boston’s Tufts University, tells WebMD.

“This association was strong, and it persisted even when we controlled for everything that we could think of that might influence risk, including calcium and vitamin D intake, fruit and vegetable consumption, and physical activity.”

Cola Drinkers Also Drank Milk

Approximately 55% of Americans, mostly women, are at risk for the brittle and thinning bone disease known as osteoporosis, according to the National Osteoporosis Foundation.

Bones naturally become thinner with age, and women are four times as likely as men to develop osteoporosis.

In addition to having a family history of osteoporosis, getting little exercise, being extremely thin, getting too little calcium and vitamin

D, and smoking all contribute to risk. More than one alcoholic drink a day also increases a woman’s risk of osteoporosis.

Earlier studies have linked cola consumption to bone loss, but doctors thought this was because cola drinkers drank less milk, which is high in bone-building nutrients.

Tucker and colleagues did not find this to be the case among women in their study. However, women who regularly drank colas did have overall lower calcium intake, possibly due to eating less.

Researchers examined data derived from 1,413 women and 1,125 men.

The men reported drinking an average of six carbonated drinks a week, with five being cola. The women reported drinking five carbonated drinks, four of which were cola.

Cola consumption did not appear to affect bone mineral density among men, but the more colas the women drank, the lower their bone mineral density.

Why Cola May Affect Bones

Tucker believes the phosphoric acid in cola may explain at least some of the observed impact on bone.

Some nutrients, like calcium, magnesium, and potassium, help keep bones strong. Others, however, including phosphoric acid, are considered negative influences on bone health.

“Physiologically, a diet low in calcium and high in phosphorus may promote bone loss, tipping the balance of bone remodeling toward calcium loss from the bone,” Tucker says.

Critics of the theory counter that the amount of phosphoric acid in cola is negligible compared with other dietary sources, such as chicken or cheese. Tucker says controlled studies are needed to answer the question.

The findings are published in the October issue of the American Journal of Clinical Nutrition.

More Study Needed

Fran Tylavsky, DrPH, says the study is interesting but falls short of proving a link between cola consumption and bone loss in women.

Studies comparing bone loss over time among regular cola drinkers and noncola drinkers would be needed to confirm such an association, she says.

Tylavsky, a professor of preventive medicine at the University of Tennessee, Memphis, says it is increasingly clear that the same diet recommended for lowering heart risk, obesity, diabetes, and cancer is also good for bone health.

That means eating plenty of fruits and vegetables and limiting saturated fats and highly refined foods such as sweets, white bread, and white rice.

Including low-fat dairy foods in the diet is also important, she says, because dairy foods not only contain calcium, but also magnesium and potassium — nutrients that are vital in building and maintaining strong bones.

“Bones break down and build up throughout your life,” she says. “That is how they stay strong. Bones need adequate nutrients as we grow and as we get older to help bones repair.”

SOURCES: Tucker, K.L. American Journal of Clinical Nutrition, October 2006; vol 84: pp 936-942. Katherine L. Tucker, PhD, professor of nutritional epidemiology, Tufts University, Boston. Fran Tylavsky, DrPH, professor of preventive medicine, University of Tennessee Health Science Center, Memphis.