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Contemp Clin Trials Commun. 2016 Aug 2;4:105-117. doi: 10.1016/j.conctc.2016.06.013. eCollection 2016 Dec 15.

A randomized placebo-controlled trial of the effect of coffee consumption on insulin sensitivity: Design and baseline characteristics of the Coffee for METabolic Health (COMETH) study.

Author information

1
NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore.
2
Saw Swee Hock School of Public Health, National University of Singapore, Singapore.
3
Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
4
Division of Endocrinology, National University Hospital, National University Health System, Singapore.
5
Investigational Medicine Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
6
Nestlé Clinical Development Unit, Lausanne, Switzerland.
7
Gastrointestinal Health & Microbiome, Nestlé Institute of Health Sciences, Lausanne, Switzerland.
8
Nutrition & Health Research, Nestlé Research Center, Lausanne, Switzerland.

Abstract

Background:

Coffee 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.

Methodology:

The 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.

Discussion:

If 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 registration:

ClinicalTrials.gov identifier: NCT01738399. Registered on 28 November 2012. Trial Sponsor: Nestlé Research Center, Lausanne, Switzerland. Trial Site: National University of Singapore.

KEYWORDS:

Coffee; Hyperinsulinemic euglycemic clamp; Insulin resistance; Insulin sensitivity; Non-insulin dependent diabetes mellitus; Type 2 diabetes

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