NHANES nutrition research may be flawed

October 14, 2013

A new study published in PLOS ONE shows that four decades of nutrition research funded by the Centers for Disease Control and Prevention (CDC) may be invalid because the method used to collect the data was flawed.

The study, led by Arnold School of Public Health (University of South Carolina) Exercise Scientist and Epidemiologist Edward Archer, has demonstrated limitations in the measurement protocols used in the National Health and Nutrition Examination Survey (NHANES). The findings reveal that a majority of the nutrition data collected by the NHANES are not “physiologically credible,” said Archer.

The NHANES is the most comprehensive compilation of data on the health of children and adults in the United States. The survey combines interviews of self-reported food and beverage consumption over 24 hrs and physical examinations to assess the health and nutritional status of the U.S. population. Conducted by the CDC and the U.S. Dept. of Agriculture, the NHANES is the primary source of data used by researchers studying the impact of nutrition and diet on health.

The study examined data from 28,993 men and 34,369 women, 20–74 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,” said Archer.

In other words, 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% and 41% (i.e., 716 and 856 calories per-day, respectively).

“Throughout its history, the NHANES survey has failed to provide accurate estimates of the habitual caloric consumption of the U.S. population,” said Archer. “Although improvements were made to the NHANES measurement protocol after 1980, there was little improvement to the validity of U.S. nutritional surveillance.”

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.