Data Source and Methods
Data from the National Health and Nutrition Examination Surveys (NHANES) 1999-2014 were used to create these visualizations. NHANES is a cross-sectional survey designed to monitor the health and nutritional status of the civilian noninstitutionalized U.S. population using highly stratified, multistage probability designs. The survey consists of interviews conducted in participants’ homes and standardized health examinations conducted in mobile examination centers (MECs). During the MEC exam, a 24-hour dietary recall is administered in addition to medical and dental examinations, physiological measurements and laboratory tests. The 24-hour recalls are conducted in English or Spanish. These dietary interviews are conducted by dietary interviewers. Survey participants 12 years and older complete the dietary interview on their own. Proxy respondents report for children who are 5 years and younger and for other persons who cannot self-report. Proxy-assisted interviews are conducted with children 6-11 years of age. Beginning in 2002, all participants were asked to complete a second 24-hour dietary recall (Day 2) interview. The NHANES Day 2 dietary recalls are collected by telephone approximately 3 to 10 days after the MEC exam using U.S. Department of Agriculture’s (USDA’s) automated multiple-pass method. Each reported food or beverage was assigned a food code from the USDA Food and Nutrient Database for Dietary Studies (FNDDS) with corresponding nutrient content by weight. All analyses were conducted using a statistical software SUDAAN that accounts for the complex multistage probability sampling design and 1-day dietary sample weights were used to account for nonresponse and weekend/weekday recalls. Estimates for adults (20+ years) were age-adjusted using age distributions from the 2000 US Census.
NHANES Oversampling by Race/Ethnicity
For NHANES 1999-2006, oversampling was performed for Mexican-American Hispanic persons. Consequently, the largest proportion Hispanic persons included in NHANES 1999-2006 were Mexican American. In 2007-2010, the sample design was changed to oversample all Hispanic persons. Additionally, Asians were oversampled starting in NHANES 2011-2014 in addition to the ongoing oversample of Hispanics, non-Hispanic blacks, older adults, and low income white and other persons. These changes in oversampling methodology influence interpretation of results for Hispanic populations across NHANES cycles and explain the limited data availability for Asian population in earlier NHANES cycles.
For more information about the National Health and Nutrition Examination Survey, please visit the NHANES website at: http://www.cdc.gov/nhanes.