Assessing habitual food consumption is challenging in multi-ethnic cosmopolitan settings. We systematically developed a semi-quantitative food frequency questionnaire (FFQ) in a multi-ethnic population in Singapore, using data from two 24-h dietary recalls from a nationally representative sample of 805 Singapore residents of Chinese, Malay and Indian ethnicity aged 18–79 years. Key steps included combining reported items on 24-h recalls into standardized food groups, developing a food list for the FFQ, pilot testing of different question formats, and cognitive interviews. Percentage contribution analysis and stepwise regression analysis were used to identify foods contributing cumulatively ≥90% to intakes and individually ≥1% to intake variance of key nutrients, for the total study population and for each ethnic group separately. Differences between ethnic groups were observed in proportions of consumers of certain foods (e.g., lentil stews, 1%–47%; and pork dishes, 0%–50%). The number of foods needed to explain variability in nutrient intakes differed substantially by ethnic groups and was substantially larger for the total population than for separate ethnic groups. A 163-item FFQ covered >95% of total population intake for all key nutrients. The methodological insights provided in this paper may be useful in developing similar FFQs in other multi-ethnic settings.

Background In observational studies, coffee consumption has been consistently associated with a lower risk of type 2 diabetes mellitus. Trials examining the effect of coffee consumption on glucose metabolism have been limited by the use of surrogate insulin sensitivity indices, small sample sizes, lack of blinding, and short follow-up duration. Objectives We aimed to overcome limitations of previously conducted coffee trials in a randomized placebo-controlled trial of the effect of coffee consumption on insulin sensitivity. Methods We conducted a 24-wk randomized placebo-controlled trial in 126 overweight, non–insulin sensitive (HOMA-IR ≥1.30), Chinese, Malay, and Asian-Indian males and females aged 35–69 y. Participants were randomly assigned to receive 4 cups of instant regular coffee (n = 62) or 4 cups of a coffee-like placebo beverage (n = 64) per day. The primary outcome was the amount of glucose metabolized per kilogram of body weight per minute (Mbw) assessed during steady-state conditions with a hyperinsulinemic euglycemic clamp. Secondary outcomes included other clamp-based insulin sensitivity measures, biological mediators of insulin sensitivity, and measures of fasting glucose metabolism. Results Coffee consumption did not significantly change insulin sensitivity compared with placebo (percentage mean difference in Mbw = 4.0%; 95% CI: −8.3, 18.0%; P = 0.53). Furthermore, no significant differences in fasting plasma glucose (2.9%; 95% CI: −0.4, 6.3%; P = 0.09) or biological mediators of insulin resistance, such as plasma adiponectin (2.3%; 95% CI: −1.4, 6.2%; P = 0.22), were observed between coffee and placebo groups over 24 wk of intervention. Participants in the coffee arm experienced a loss of fat mass (FM) (−3.7%; 95% CI: −6.3, −1.1%; P = 0.006) and reduction in urinary creatinine concentrations (−21.2%; 95% CI: −31.4, −9.5%; P = 0.001) compared with participants in the placebo arm over 24 wk of intervention. Conclusions Consuming 4 cups/d of caffeinated coffee for 24 wk had no significant effect on insulin sensitivity or biological mediators of insulin resistance but was associated with a modest loss of FM and reduction in urinary creatinine concentrations. This trial was registered at clinicaltrials.gov as NCT01738399. Registered on November 28, 2012. Trial sponsor: Nestlé Research, Lausanne, Switzerland. Trial site: National University of Singapore.

BackgroundCoffee consumption has been consistently associated with a lower risk of type 2 diabetes mellitus in cohort studies. In addition, coffee components increased insulin sensitivity in animal models. However, data from intervention studies on the effect of coffee consumption on glucose metabolism have been limited by small sample sizes, lack of blinding, short follow-up duration and the use of surrogate indices of insulin sensitivity. We designed the Coffee for Metabolic Health (COMETH) study to evaluate the effect of coffee consumption on insulin sensitivity.MethodologyThe COMETH study is a double-blind randomized placebo-controlled 24-week trial. Participants were overweight, male and female habitual coffee consumers who were of Chinese, Malay and Asian-Indian ethnicity. We excluded smokers, persons with diabetes, and persons with low insulin resistance (HOMA-IR < 1.30). Participants were randomly assigned to receive daily 4 cups of instant regular coffee or 4 cups of a coffee-like placebo beverage. The hyperinsulinemic euglycemic clamp was performed at baseline and at the end of 24 weeks to determine changes in the bodyweight standardized M-value. Secondary outcomes included changes in fasting glucose and insulin sensitivity mediators such as adiponectin, markers of inflammation, liver function, and oxidative stress.We enrolled 128 participants, 126 (57.1% males; aged 35–67 years) of whom completed baseline assessments.DiscussionIf improvement in insulin sensitivity in the coffee group is significantly greater than that of the placebo group, this would support the hypothesis that coffee consumption reduced risk of type 2 diabetes through biological pathways involving insulin sensitivity.Trial registrationClinicalTrials.gov identifier: NCT01738399. Registered on 28 November 2012. Trial Sponsor: Nestlé Research Center, Lausanne, Switzerland. Trial Site: National University of Singapore.