University of South Carolina study shows flaws in NHANES
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 seriously flawed, according to a new study by the Arnold School of Public
Health at the University of South Carolina.
The study, led by Arnold School exercise scientist and epidemiologist Edward
Archer, has demonstrated significant limitations in the measurement protocols
used in the National Health and Nutrition Examination Survey (NHANES). The
findings, published in PLOS ONE (The Public Library of Science), reveal that a
majority of the nutrition data collected by the NHANES are not "physiologically
credible," Archer said.
These results suggest 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, he said.
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 hours and physical
examinations to assess the health and nutritional status of the US population.
Conducted by the CDC and the U.S. Department 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 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.
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 percent and 41 percent (i.e., 716 and 856 Calories per-day
"Throughout its history, the NHANES survey has failed to provide accurate
estimates of the habitual caloric consumption of the U.S. population," Archer
said. "Although improvements were made to the NHANES measurement protocol after
1980, there was little improvement to the validity of U.S. nutritional
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, who conducted the study with colleagues at
the Arnold School.
"The nation's major surveillance tool for studying the relationships between
nutrition and health is not valid. It is time to stop spending tens of millions
of health research dollars collecting invalid data and find more accurate
measures," he said.
To access the current study, please visit: http://dx.plos.org/10.1371/journal.pone.0076632.