Using Intake Biomarkers to Evaluate the Extent of Dietary Misreporting
Summary: A study assessing dietary measurement error using
two self-report instruments (a food frequency questionnaire and 24-hour recall)
and unbiased biomarkers of energy and protein intake (doubly labeled water and
urinary nitrogen) found that men and women underreported both protein and energy
intakes on both instruments. These findings have important implications for
nutritional epidemiology and dietary surveillance.
Reference: Subar AF, Kipnis V, Troiano RP, Midthune D,
Schoeller DA, Bingham S, Sharbaugh CO, Trabulsi J, Runswick S, Ballard-Barbash
R, Sunshine J, Schatzkin A. Using intake biomarkers to evaluate the extent of
dietary misreporting in a large sample of adults: the OPEN study. Am J
Epidemiol 2003;158(1):1-13.
Nutritional epidemiologists and nutritionists rely on self-reported dietary
information when they conduct research and surveillance activities. This
information is often derived from food frequency questionnaires (FFQs), which
attempts to measure a person's usual intake over a defined time (usually a
year). Although it is well known that this information contains errors, the
qualitative and quantitative nature of these errors is not well understood. As
a result, to evaluate measurement error in FFQs and correct for it, some
investigators have incorporated "reference" instruments, such as 24-hour dietary
recalls (24HRs), which record in detail everything consumed in the previous 24
hours, or food records. However, several studies using dietary intake
biomarkers have found significant bias (generally underreports) in these
instruments as well. Understanding the structure and extent of dietary
measurement error is essential to interpreting findings from nutritional
epidemiology and surveillance studies.
The Observing Protein and Energy Nutrition (OPEN)
Study examined dietary measurement error in FFQs and 24HRs by using doubly
labeled water (DLW) and urinary nitrogen as unbiased biomarkers of total energy
expenditure and protein intake. A total of 484 people aged 40-69 and living in
the Washington DC suburb of Montgomery County, MD, participated in the September
1999 to March 2000 study. Over the course of three visits with study staff,
OPEN participants completed two FFQs, two 24HRs, and several other
health-related questionnaires. They were dosed with doubly labeled water,
provided several spot urine samples, completed two 24-hour urine collections,
and had their height and weight measured.
Similar to the results of previous studies, OPEN found underreporting of both
energy and protein intakes. On the 24HRs, 9% of men and 7% of women were
defined as underreporters; on the FFQs, 35% of men and 23% of women were
underreporters. On average, compared to their total energy expenditure, men
underreported energy intake by 12-14% on 24HRs and 31-36% on FFQs; compared to
the protein biomarker, they underreported protein intake by 11-12% on 24HRs and
by 30-34% on FFQs. Compared to their total energy expenditure, women
underreported energy intake by 16-20% on 24HRs and 34-38% on FFQs; compared to
the protein biomarker, they underreported protein intake by 11-15% on 24HRs and
by 27-32% on FFQs.
Several trends also emerged from the data:
- as total energy expenditure or protein intake increased, so too did underreporting;
- underreporting tended to increase with body mass index; and
- underreporting of energy was somewhat greater than that of protein, suggesting greater underreporting of fat, carbohydrate, and alcohol.
These findings have important implications for nutritional epidemiology and
dietary surveillance, particularly for the use of these instruments to measure
intake of key dietary components, such as fat and energy. The authors conclude
that work to further elucidate the issues examined in this study will help
support the nutritional epidemiology and dietary surveillance research that is
central to answering questions about diet's relationship to disease.
Learn more about the Risk Factor
Monitoring and Methods Branch's activities related to biomarkers.
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