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Definition |
Information on rice consumption was first assessed in 1980 in NHS participants using a validated semi-quantitative food frequency questionnaire (SFFQ), and repeated in 1984, 1986, and every 4 years thereafter. Similar SFFQs were administered every 4 years for NHS II participants during 1991 through 2009 and for HPFS participants during 1986 through 2008. In each SFFQ, we asked the participants how often, on average over the past year, they consumed a specified portion size of each food, with nine possible frequency choices ranging from “almost never” to “6 or more times per day”. For white rice and brown rice, we used 1 cup as the serving unit. The total rice intake was calculated as the sum of white rice and brown rice. In the current study, we categorized participants’ rice intake into 4 categories (< 1 serving per week, 1 serving per week, 2-4 servings per week and ≥ 5 servings per week). The reproducibility and validity of these SFFQs have been evaluated in detail elsewhere16-19. Assessments of white rice and brown rice consumption were moderately correlated with diet record assessments. For example, the corrected Pearson correlation coefficients between these 2 assessments were 0.53 for white rice and 0.41 for brown rice in the HPFS
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