What is the OPEN Study?

The Observing Protein and Energy Nutrition Study was an NCI-sponsored study designed to assess dietary measurement error by comparing results from self-reported dietary intake data with four dietary biomarkers: doubly labeled water and urinary nitrogen, sodium, and potassium. The study was conducted from July 1999 to March 2000 and included 484 men and women, aged 40-69 years old, living in Montgomery County, Maryland.