Flawed methodology may bring down 40 years of nutrition research, a new study suggests. Scientists from the Arnold School of Public Health at the University of South Carolina have demonstrated that the exhaustive research effort founders on significant limitations in its measurement protocols. Without an accurate picture of the population’s health and diet, the collected data may not be “physiologically credible.”

The challenged data comes from the National Health and Nutrition Examination Survey (NHANES) – a research program that has been administered and funded by the Centers for Disease Control and Prevention (CDC) for the past 40 years. The program currently represents the most comprehensive compilation of the health of U.S. children and adults. It derives its data from physical examinations as well as interviews.

Now, the methodology underpinning NHANES’s interpretation and collection of public health data is being called into question by a team of researchers led by Edward Archer, an exercise scientist and epidemiologist. According the Archer, the compiled nutrition data is not “physiologically credible,” as it would be impossible to survive on the reported caloric intake.

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

Published in the journal PloS ONE, the study examined NHANES data from 28,993 men and 34,369 women from 1971 to 2010. Archer and his colleagues identified a consistent discrepancy between the reported intake and expenditure of calories. In other words, subjects tended to downplay the amount of calories they consumed. This underreporting was particularly prevalent among obese men and women, who on average understated their intake by 25 percent and 41 percent respectively – or, about 800 calories per day.

“The nation's major surveillance tool for studying the relationships between nutrition and health is not valid,” Archer argued. “It is time to stop spending tens of millions of health research dollars collecting invalid data and find more accurate measures,"

Hopefully, the new study will help restore accuracy to the NHANES by prompting a reevaluation of its current assessment tools.

Source: Archer E, Hand GA, Blair SN (2013) Validity of U.S. Nutritional Surveillance: National Health and Nutrition Examination Survey Caloric Energy Intake Data, 1971–2010. PLoS ONE 8(10): e76632. doi:10.1371/journal.pone.0076632