The MEC is a population-based prospective cohort established in 1993–1996; it consists of men and women aged 45–75 years in Hawaii and California (Kolonel et al. 2000
). Participants entered the cohort by completing a 26-page, self-administered questionnaire that included a validated food frequency questionnaire (FFQ) and questions about demographics, medical history, anthropometric measures, and lifestyle factors (Stram et al. 2000
). The Institutional Review Boards at the University of Hawaii and Kaiser Permanente Hawaii approved the study.
We calculated food and nutrient intakes as g/day using an ethnicity-specific food composition database. Soy intake estimated from reported consumption of tofu, miso soup, and vegetarian-meat products was categorized into low, moderate, and high (<5, 5-<10,≥ 10 g/day).
In the Hawaii component of the MEC, comprised of 103,898 primarily Caucasian, Japanese American, and Native Hawaiian participants, we were able to identify incident diabetes cases through linkages with health plans in addition to follow-up questionnaires (Maskarinec et al. 2009
). After excluding 10,028 self-reported cases at baseline, 8,797 participants of other ethnicities, 812 unconfirmed cases, 8,917 individuals with missing covariates, dietary information, or follow-up information, 75,344 participants were part of the analysis.
Using the SAS software, version 9.2 (SAS Institute, Cary, NC, USA), Cox regression was applied to calculate hazard ratios (HR) and 95% confidence intervals (CI). The models were stratified by age at cohort entry and adjusted for ethnicity, body mass index (BMI), physical activity (quintiles of Metabolic Equivalent of Tasks), education (≤12, 12-<15, and ≥15 years), energy intake (log-transformed), smoking status (never, past, and current), and intakes of alcohol (quintiles), dietary fiber (log-transformed), and processed red meat (log-transformed) (Hopping et al. 2010
; Erber et al. 2010
; Steinbrecher et al. 2010
). We also performed stratified analyses by sex, ethnicity, and weight status. Ethnic-specific cut-offs for overweight and obesity were applied: 25 and 30 kg/m2
for Caucasians and Native Hawaiians and 23 and 27.5 kg/m2
for Japanese Americans (WHO expert consultation 2004