CHAPEL HILL -- Between 1965 and 1996, a considerable shift occurred in the diets of U.S. teen-agers that could compromise the future health of the nation's people, a major new University of North Carolina at Chapel Hill study shows. On the horizon, researchers say, are more strokes, heart disease, high blood pressure and cases of the bone-weakening condition known as osteoporosis.
Total milk consumption dropped by close to 50 percent among adolescents over the three decades studied, they found. That decrease was accompanied by a heavy increase in consumption of sugar-laden soft drinks and fruit-flavored beverages. Teens also began eating more of their vegetables in the form of fatty fried potatoes than their parents did.
"An increase in high-fat potato consumption through French fries and hash browns led to an increase in vegetable intake, but the number of servings of fruits and vegetables is still below the recommended five per day," said Dr. Barry Popkin, professor of nutrition at the UNC-CH schools of public health and medicine. "Iron, folate and calcium intakes continue to be below recommendations for girls."
A report on the findings appears in the July issue of Archives of Disease in Childhood, a professional journal. Besides Popkin, authors are Drs. Claude Cavadini, a scientist at Nestle Research Center in Lausanne, Switzerland, and Anna Maria Siega-Riz, assistant professor of nutrition and of maternal and child health.
The researchers conducted their study to uncover adolescent food consumption trends that could affect chronic diseases in the United States. They analyzed dietary survey information from a subset of 12, 498 teens from an original group of 90,000 participants in four U.S. Department of Agriculture surveys that began in 1965.
"Some of the quite drastic changes we've seen are good, like teens switching from high-fat to low-fat milk, but many are troubling, the most profound being this immense increase in soft drink and sugared-drink consumption in general," Popkin said. "There's also a very large increase, particularly among boys, in higher-fat, grain-based dishes such as pizza, tacos, tortillas and lasagna."
A tripling of sugar intake in drinks by teens over the 30 years is of special concern, he said.
"Sugar itself is not bad for you, but what's bad about sugar is that it has no nutrients and either people use it in a way that takes the place of other nutrients such as calcium for teen-agers or they eat extra food that contributes to obesity," Popkin said.
Previous studies have shown recent highs level of soft drink consumption and decreased physical activity, but the new research paper is the first to document them over such a long time span, the scientist said. Less milk drinking will lead to more bone problems, especially for women as they age.
"Our results show a small decrease in total energy intake and total fat over the period studied, the latter of which is positive, but also a decrease in raw fruits, non-potato sources of vegetables and calcium-rich dairy sources," the authors wrote. "Many national surveys that focus on adolescents, such as the Youth Risk Behavior Surveillance System (funded by the Centers for Disease Control and Prevention) and the National Longitudinal Survey of Adolescent Health (funded by the National Institutes of Health) lack the appropriate dietary data to quantify these trends."
That teens are consuming 17 percent less energy than in the 1960s but still are gaining weight likely can be explained by their significantly lower levels of physical activity, they said. Other concerns the analysis revealed were inadequate fiber and non-potato vegetable intake.
"This population does not consume other sources of fiber such as whole grains, pasta, rice, bread and high-fiber cereals in sufficient quantities to make a difference in the total fiber intake, the authors wrote. "Thus, not only are adolescents at risk of chronic diseases because of low-fiber intake but also because of low anti-oxidant and non-nutrient sources of plant foods, which may serve as protective factors for certain cancers."
The Nestle Research Center sponsored the research.
By DAVID WILLIAMSON
UNC-CH News Services
Note: Call Popkin and Siega-Riz at 919-966-1732 and 962-8410, respectively. Copies of the paper can be found at: http://adc.bmjjournals.com/cgi/content/full/archdischild;83/1/18.
School of Public Health Contact: Lisa Katz, 919-966-7467.
Journal
Archives of Disease in Childhood