Forty years of government-funded nutrition research may be invalid because the data collection method was critically flawed, according to a new study by the Arnold School of Public Health at the University of South Carolina.
The study findings, published in PLOS (The Public Library of Science) ONE , suggest that a majority of the nutrition data collected by the National Health and Nutrition Examination Survey (NHANES), funded by the Centers for Disease Control and Prevention (CDC), are not "physiologically credible," said Arnold School scientist Edward Archer, who conducted the research, in a university release.
Their analysis suggests that without valid population-level data, speculations regarding the role of energy intake in the rise in the prevalence of obesity are without empirical support, said Archer. Conducted by the CDC and the U.S. Department of Agriculture, the NHANES is the motherlode of data on the health of Americans. It combines interviews of self-reported food and beverage consumptions over 24 hours and physical examinations to assess the health and nutritional status of the U.S. population. It's the primary source of data used by researchers studying the impact of nutrition and diet on health. If invalid, it may question the validity of scores of research based on the NHANES, like a study last year that found that blood levels of trans-fatty acids in white adults in the U.S. population decreased by 58 percent from 2000 to 2009.
The new examination of the NHANES examined data from 28,993 men and 34,369 women, 20 to 74 years old, from NHANES I (1971 – 1974) through NHANES (2009 – 2010), and looked at the caloric intake of the participants and their energy expenditure, predicted by height, weight, age and sex. The results show that -- based on the self-reported recall of food and beverages -- the vast majority of the NHANES data "are physiologically implausible, and therefore invalid," Archer said. Basically, the "calories in" reported by participants and the "calories out," don't add up and it would be impossible to survive on most of the reported energy intakes. This misreporting of energy intake varied among participants, and was greatest in obese men and women who underreported their intake by an average 25 percent and 41 percent -- they were off by about 716 and 856 calories a day. Yes, math has never been among Americans' strong points.
"Throughout its history, the NHANES survey has failed to provide accurate estimates of the habitual caloric consumption of the U.S. population," Archer said. These limitations "suggest that the ability to estimate population trends in caloric intake and generate public policy relevant to diet-health relationships is extremely limited," said Archer.
Unfortunately, public policy cannot be based on the widening of airline seats, the growth of the XXX Large section at box stores and the popularity of creations like Wendy's Baconator ( two beef patties layered with bacon and cheese).
"The nation's major surveillance tool for studying the relationships between nutrition and health is not valid," said Archer. "It is time to stop spending tens of millions of health research dollars collecting invalid data and find more accurate measures," he said.