A University of Missouri consumer economist, analyzing the results of a national food survey, found that people significantly increased their chances of being deficient in the recommended daily allowances (RDA) for common vitamins and minerals when they consumed a lot of sugared drinks.
RDA deficiencies are not common. In the some 15,000 people who self-reported their food intake for the U.S. Department of Agriculture (USDA) study, from only 1 percent to 8 percent of the participants were not getting the proper amounts of certain vitamins and minerals.
However, says Michael S. Finke, an assistant professor or consumer and family economics at Missouri, the consequences of getting ever more calories from soft drinks or fruit-flavored sugared drinks with no nutrients is a trend that needs attention.
"RDA deficiency is not a major problem because a lot of foods have vitamins and minerals added, but this study shows that more nutrient-rich foods are being replaced by sugar drinks," says Finke, author of the study, appearing in the December issue of the Family and Consumer Sciences Research Journal.
"People haven't really highlighted the consequences of this major food consumption trend," he says.
Part of the problem could be simple economics, he says. Soda is a very cheap way to get calories.
"Soda pop has always been around, but it's so much cheaper now, relatively speaking, than it was 30 years ago that it is an enticing food option for resource-constrained families," Finke says. "A three-liter bottle of soda is 69 cents and contains 1,000 calories."
The only cheaper food source, he says, is vegetable oils.
Between 1970 and 1997, Finke says in his study, there has been a 86 percent increase in annual per capita consumption of carbonated, sugared soft drinks. One 12-ounce can of cola supplies about 150 calories from about 10 teaspoons of sugar.
In the study, Finke reviewed the results of a 1994-1996 survey of the USDA's Food Intakes by Individuals, to see if there were any associations between soda consumption and vitamin and mineral deficiency among participants in the self-reported food survey.
The scientists looked at 14 vitamins and minerals, including: vitamins A, E, C, B6, and B12, thiamin, riboflavin, niacin, and folate, and the minerals calcium, phosphorus, magnesium, iron, and zinc. The study did not include information about any vitamin or mineral supplements taken.
"The results were a little bit more dramatic that I had expected," he says. "I expected the results would be significant for nutrients associated with foods that might be replaced by soda, like calcium in milk, but the results were also significant for every other vitamin and mineral."
Finke and his colleagues found that sugar drink consumption was the most consistent variable -- more than gender, race, or income -- to signal the probability that people would not meet their RDA requirements.
The problem, he says, is not failure to meet RDA requirements, as only a small proportion of the participants actually failed to do so, ranging from 181 people (1.2 percent) for niacin to 1,168 people (7.8 percent) for vitamin A. However, the trend of increased soda pop consumption could increase the likelihood that more people would fail to meet their RDA requirements down the road.
"If someone drinks two cans of soda daily, which is about 15 percent of daily caloric intake, there is a 1 percent decrease in the probability that the person will meet their RDA requirements in calcium, for instance," Finke says. "So if the trend continues in the future as it has in the past, sugar drink consumption will have an even greater impact on failure to meet RDA's."
Finke says he is an economist, not a nutritionist, "but it seems obvious that we should pay attention to this trend in U.S. food consumption and look at things we can to do reduce sugared drink consumption by making other foods less expensive and more palatable."
Connie Diekman, a nutritionist at the Washington University in St. Louis, agrees that soft drink consumption is a trend threatening to compromise good, nutritional health, especially in young people.
"What this study and others have shown is that adolescents increasingly turn to soft drinks for hydration and then don't need to get those calories from healthier choices," she says. "In addition, the long-term effects of inadequate calcium -- maybe not deficient, but less than that needed for bone health -- are a major health issue."
What To Do
See a report on soda consumption by teens at the Center for Science in the Public Interest. Go to the American Dietetic Association for some tips on how much soda to consume.