Too Much Soda May Take Some Fizz Out of the Bones

Preliminary findings suggest that drinking lots of non-diet sodas coupled with eating few leafy greens may compromise bone building and maintenance, according to an Agricultural Research Service study. It's a dietary combination quite common among U.S. youths.

Drinking 57 ounces--close to 5 cans--of sugary sodas each day for weeks at a stretch upset the calcium and phosphorus balances of 11 young men in the study. And the effect on these bone minerals was greatest while the experimental diets were low in magnesium, according to Forrest Nielsen and David Milne at the Grand Forks, N.D., Human Nutrition Research Center.

Non-diet sodas are a major source of fructose in the U.S. diet. Leafy greens, nuts and whole grains are rich in magnesium. But 38 percent of U.S. males over age 19--and 39 percent of male teens--get less than 75 percent of the recommended magnesium intake through foods, according to recent USDA consumption data. Statistics for females are worse: 46 percent over age 19 and 60 percent of teens.

Males drink more regular soft drinks, however, averaging close to one 12-ounce can daily. Teenage males average about 20 ounces a day. And some regularly consume as much as the study volunteers.

All that soda put the volunteers "in the red" for phosphorus. They excreted more than they absorbed--both when they got adequate magnesium and when they got half the Recommended Dietary Allowance (RDA). Besides being a major bone mineral, phosphorus is central to cells' energy production system and is integral to DNA and its sister RNA.

The volunteers' calcium balance remained positive but dropped, especially during the low-magnesium period. In addition, an enzyme that indicates bone formation and breakdown increased in the men's blood when they consumed excess fructose.

Scientific contacts: Forrest H. Nielsen or David Milne, Grand Forks Human Nutrition Research Center, P.O. Box 9034, University Station, Grand Forks, N. Dak. 58202-9034, phone (701) 795-8353, fax (701) 795-8395; fnielsen@gfhnrc.ars.usda.gov, dmilne@gfhnrc.ars.usda.gov.