Coffee and Metabolic Health Outcomes

Coffee is a major source of the phenolic acid chlorogenic acid and a substantial source of trigonelline, niacin, lignans magnesium, and potassium. Several of these compounds have been shown to improve glucose metabolism in animal models. Consumption of coffee was inversely associated with the risk of type-2 diabetes in prospective cohort studies across the world. Consumption of 3 to 4 cups of coffee per day was associated with an approximately 25% lower risk of type-2 diabetes. However, direct evidence of the efficacy of coffee to reduce blood glucose and insulin resistance parameters in humans from randomized trials is still lacking. In recent small trials of short duration (up to 6 weeks) coffee consumption increased levels of the insulin-sensitizing hormone adiponectin, but did not significantly improve insulin sensitivity These results suggest that a larger longer-term trial of the effects of coffee consumption on directly measured insulin sensitivity is warranted.

Inclusion criteria

• Subjects classified as being insulin-resistant in the screening visit. Subjects should have a non-diabetic fasting plasma glucose concentration (< 7.0 mM) and a HOMA-IR > 2.2. The HOMA-IR was demonstrated as a reliable indicator of insulin resistance strongly correlated with values obtained by clamp (4). The cut-off value of the HOMA-IR was defined according to data obtained in the Singapore cohort. It corresponds to the 75th percentile of the population. The HOMA-IR cut-off was subsequently revised to ≥ 1.3 to increase recruitment rates.
• Age: ≥ 35 to ≤ 69 years old
• Body mass index : ≥ 22.5 to ≤ 35.4 kg/m2
• Users of at least 1 cups of caffeinated coffee per day who are willing to be randomized to any of the interventions.
• Subjects should be willing to stop consuming caffeinated soft drinks or supplements during the study and to drink coffee with non-dairy creamer.
• Non-smokers (< 1 cigarette per week)
• Participants have been weight stable for at least -8 weeks pre-ceding the screening visit (± 2.5 kgs).
• Chinese, Malay and Indian ethnicity

Exclusion criteria

Subjects representing one or more of the following criteria are excluded from participation in the study:

• Any condition/illness that may affect the study outcomes or would make participation potentially harmful such as pregnancy or breastfeeding, diabetes mellitus, heart disease, stroke, hypertension, malabsorption syndromes, GERD, a history of ulcer, clotting or bleeding disorders,allergy to the test beverage, allergy to insulin, according to a detailed medical history.
• Participants who are allergic to foods may be excluded based on the investigator's discretion.
• Participants consume > 2 alcoholic servings/day on a regular basis and > 8 caffeinated servings (based on tea and coffee)/day
• Present drug abuse or use of medications that could interfere with the treatment including bronchodilators, quinolone antibiotics, monoamine oxidase inhibitors, anxiolytics, ranitidine, corticosteroids, growth hormone, anti-hypertensives. These conditions will be screened based on subject reporting. Participants will be asked to bring in their current medications at the time of screening, and these will be checked by the study-staff.
• Subject is taking traditional medications, herbal or dietary supplements that may affect the study outcome in the opinion of the investigators.
• Subject who cannot be expected to comply with the study procedures in the opinion of the investigators.
• Currently participating or having participated in another clinical trial during the last 12 weeks prior to the beginning of this study.
• Premenopausal women with self-reported irregular menstrual cycles or peri-menopausal women (participants who stopped getting their menses for less than 48 weeks ).