Using Intake Biomarkers to Evaluate the Extent of Dietary Misreporting in a Large Sample of Adults: The OPEN Study

TLDR

The study aimed to evaluate dietary measurement error by comparing self‑reported energy and protein intake from a food frequency questionnaire and 24‑hour recall with unbiased biomarkers of energy (doubly labeled water) and protein (urinary nitrogen). The OPEN Study recruited 484 adults aged 40–69 from Montgomery County, Maryland, and assessed their dietary intake using the FFQ and 24‑hour recall alongside doubly labeled water and urinary nitrogen measurements. Men underreported energy intake by 12–14% on 24‑hour recalls and 31–36% on food frequency questionnaires, while women underreported by 16–20% and 34–38% respectively; protein intake was underestimated by 11–12% and 30–34% in men and 11–15% and 27–32% in women, with only minimal underreporting of the percentage of energy from protein, underscoring the need for biomarker‑based validation in nutritional epidemiology.

Abstract

This paper describes the Observing Protein and Energy Nutrition (OPEN) Study, conducted from September 1999 to March 2000. The purpose of the study was to assess dietary measurement error using two self-reported dietary instruments-the food frequency questionnaire (FFQ) and the 24-hour dietary recall (24HR)-and unbiased biomarkers of energy and protein intakes: doubly labeled water and urinary nitrogen. Participants were 484 men and women aged 40-69 years from Montgomery County, Maryland. Nine percent of men and 7% of women were defined as underreporters of both energy and protein intake on 24HRs; for FFQs, the comparable values were 35% for men and 23% for women. On average, men underreported energy intake compared with total energy expenditure by 12-14% on 24HRs and 31-36% on FFQs and underreported protein intake compared with a protein biomarker by 11-12% on 24HRs and 30-34% on FFQs. Women underreported energy intake on 24HRs by 16-20% and on FFQs by 34-38% and underreported protein intake by 11-15% on 24HRs and 27-32% on FFQs. There was little underreporting of the percentage of energy from protein for men or women. These findings have important implications for nutritional epidemiology and dietary surveillance.