Diabetes:

Ann Intern Med. 2004 Jan 6;140(1):I17

Harvard School of Public Health, Channing Laboratory, Harvard Medical School, and Brigham and Women's Hospital, Boston, MA.

BACKGROUND: In small, short-term studies, acute administration of caffeine decreases insulin sensitivity and impairs glucose tolerance. OBJECTIVE: To examine the long-term relationship between consumption of coffee and other caffeinated beverages and incidence of type 2 diabetes mellitus. DESIGN: Prospective cohort study. SETTING: The Nurses' Health Study and Health Professionals' Follow-up Study. PARTICIPANTS: The authors followed 41 934 men from 1986 to 1998 and 84 276 women from 1980 to 1998. These participants did not have diabetes, cancer, or cardiovascular disease at baseline. MEASUREMENTS: Coffee consumption was assessed every 2 to 4 years through validated questionnaires. RESULTS: The authors documented 1333 new cases of type 2 diabetes in men and 4085 new cases in women. The authors found an inverse association between coffee intake and type 2 diabetes after adjustment for age, body mass index, and other risk factors. The multivariate relative risks for diabetes according to regular coffee consumption categories (0, <1, 1 to 3, 4 to 5, or > or =6 cups per day) in men were 1.00, 0.98, 0.93, 0.71, and 0.46 (95% CI, 0.26 to 0.82; P = 0.007 for trend), respectively. The corresponding multivariate relative risks in women were 1.00, 1.16, 0.99, 0.70, and 0.71 (CI, 0.56 to 0.89; P < 0.001 for trend), respectively. For decaffeinated coffee, the multivariate relative risks comparing persons who drank 4 cups or more per day with nondrinkers were 0.74 (CI, 0.48 to 1.12) for men and 0.85 (CI, 0.61 to 1.17) for women. Total caffeine intake from coffee and other sources was associated with a statistically significantly lower risk for diabetes in both men and women. CONCLUSIONS: These data suggest that long-term coffee consumption is associated with a statistically significantly lower risk for type 2 diabetes. 

Coffee consumption, type 2 diabetes and impaired glucose tolerance in Swedish men and women. Agardh EE, Carlsson S, Ahlbom A, Efendic S, et al. J Intern Med. 2004 Jun;255(6):645-52.

Department of Molecular Medicine, Endocrine and Diabetes Unit, Karolinska Institutet, Stockholm, Sweden.

OBJECTIVES: The association between coffee consumption, type 2 diabetes and impaired glucose tolerance was examined. In addition, indicators of insulin sensitivity and beta-cell function according to homeostasis model assessment were studied in relation to coffee consumption. DESIGN: Population-based cross-sectional study. SETTING AND SUBJECTS: The study comprised 7949 healthy Swedish subjects aged 35-56 years residing within five municipalities of Stockholm. An oral glucose tolerance test identified 55 men and 52 women with previously undiagnosed type 2 diabetes and 172 men and 167 women with impaired glucose tolerance. Information about coffee consumption and other factors was obtained by questionnaire. RESULTS: The relative risks (adjusted for potential confounders) of type 2 diabetes and impaired glucose tolerance when drinking >/=5 cups of coffee per day compared with </=2 cups per day in men were 0.45 [95% confidence intervals (CI) 0.22-0.92] and 0.63 (CI: 0.41-0.97), respectively, and in women 0.27 (CI: 0.11-0.66) and 0.47 (CI: 0.29-0.76) respectively. In subjects with type 2 diabetes and impaired glucose tolerance, high coffee consumption (>/=5 cups day(-1)) was inversely associated with insulin resistance. In addition, in those with type 2 diabetes and in women (not in men) with impaired glucose tolerance high coffee consumption was inversely associated with low beta-cell function. In women, but not obviously in men, with normal glucose tolerance, coffee consumption was associated with a reduced risk of insulin resistance. CONCLUSIONS: The results of this study indicated that high consumers of coffee have a reduced risk of type 2 diabetes and impaired glucose tolerance. The beneficial effects may involve both improved insulin sensitivity and enhanced insulin response.

Coffee Consumption and Risk of Type 2 Diabetes Mellitus Among Middle-aged Finnish Men and Women. Tuomilehto J, Hu G, Bidel S, Lindström J, Jousilahti P. JAMA.  2004;291:1213-1219.

Department of Epidemiology and Health Promotion, National Public Health Institute; Department of Public Health, University of Helsinki; and Institute of Biomedicine, Helsinki, Finland.

CONTEXT: Only a few studies of coffee consumption and diabetes mellitus (DM) have been reported, even though coffee is the most consumed beverage in the world. OBJECTIVE:  To determine the relationship between coffee consumption and the incidence of type 2 DM among Finnish individuals, who have the highest coffee consumption in the world. DESIGN, SETTING AND PARTICIPANTS: A prospective study from combined surveys conducted in 1982, 1987, and 1992 of 6974 Finnish men and 7655 women aged 35 to 64 years without history of stroke, coronary heart disease, or DM at baseline, with 175 682 person-years of follow-up. Coffee consumption and other study parameters were determined at baseline using standardized measurements. MAIN OUTCOME MEASURES:  Hazard ratios (HRs) for the incidence of type 2 DM were estimated for different levels of daily coffee consumption. RESULTS:  During a mean follow-up of 12 years, there were 381 incident cases of type 2 DM. After adjustment for confounding factors (age, study year, body mass index, systolic blood pressure, education, occupational, commuting and leisure-time physical activity, alcohol and tea consumption, and smoking), the HRs of DM associated with the amount of coffee consumed daily (0-2, 3-4, 5-6, 7-9, 10 cups) were 1.00, 0.71 (95% confidence interval [CI], 0.48-1.05), 0.39 (95% CI, 0.25-0.60), 0.39 (95% CI, 0.20-0.74), and 0.21 (95% CI, 0.06-0.69) (P for trend<.001) in women, and 1.00, 0.73 (95% CI, 0.47-1.13), 0.70 (95% CI, 0.45-1.05), 0.67 (95% CI, 0.40-1.12), and 0.45 (95% CI, 0.25-0.81) (P for trend = .12) in men, respectively. In both sexes combined, the multivariate-adjusted inverse association was significant (P for trend <.001) and persisted when stratified by younger and older than 50 years; smokers and never smokers; healthy weight, overweight, and obese participants; alcohol drinker and nondrinker; and participants drinking filtered and nonfiltered coffee. CONCLUSION:  Coffee drinking has a graded inverse association with the risk of type 2 DM; however, the reasons for this risk reduction associated with coffee remain unclear.

Coffee and incidence of diabetes in Swedish women: a prospective 18-year follow-up study. Rosengren A, Dotevall A, Wilhelmsen L, Thelle D, Johansson S. J Intern Med. 2004 Jan;255(1):89-95.

Department of Medicine, Sahlgrenska University Hospital/Ostra, Goteborg, Sweden.

OBJECTIVES: To examine the long-term incidence of diabetes in relation to coffee consumption in Swedish women. DESIGN: Prospective longitudinal cohort study. SETTING: City of Goteborg, Sweden. SUBJECTS: A random population sample of 1361 women, aged 39-65 years, without prior diabetes or cardiovascular disease took part in a screening study in 1979-1981 with questionnaires, physical examination and blood sampling. MAIN OUTCOME MEASURES: The development of diabetes until 1999 was identified by questionnaires in a second screening and the Swedish hospital discharge register. RESULTS: Altogether, there were 74 new cases of diabetes. The risk of developing diabetes was 475 per 100 000 person-years in women who consumed two cups of coffee or less per day, 271 in women who consumed three to four cups per day, 202 with a consumption of five to six cups per day, and 267 in drinkers of seven cups or more per day. Associated hazard ratios, after adjustment for age, smoking, low physical activity, education and body mass index were 0.55 (0.32-0.95), 0.39 (0.20-0.77) and 0.48 (0.22-1.06) for daily consumption of three to four, five to six and seven cups or more, respectively, with a consumption of less than two per day as reference. Additional adjustment for serum cholesterol and triglycerides attenuated the relation between coffee and diabetes slightly, indicating a possible mediating effect on the effect of coffee by serum lipids. CONCLUSIONS: The findings of the present study support the hypothesis that coffee consumption protects from the development of diabetes in women.

Coffee consumption and risk of type 2 diabetes mellitus among middle-aged Finnish men and women. Tuomilehto J, Hu G, Bidel S, Lindstrom J, Jousilahti P. JAMA 2004 Mar 10;291(10):1213-9.

Department of Epidemiology and Health Promotion, National Public Health Institute, Helsinki, Finland.

CONTEXT: Only a few studies of coffee consumption and diabetes mellitus (DM) have been reported, even though coffee is the most consumed beverage in the world. OBJECTIVE: To determine the relationship between coffee consumption and the incidence of type 2 DM among Finnish individuals, who have the highest coffee consumption in the world. DESIGN, SETTING, AND PARTICIPANTS: A prospective study from combined surveys conducted in 1982, 1987, and 1992 of 6974 Finnish men and 7655 women aged 35 to 64 years without history of stroke, coronary heart disease, or DM at baseline, with 175 682 person-years of follow-up. Coffee consumption and other study parameters were determined at baseline using standardized measurements. MAIN OUTCOME MEASURES: Hazard ratios (HRs) for the incidence of type 2 DM were estimated for different levels of daily coffee consumption. RESULTS: During a mean follow-up of 12 years, there were 381 incident cases of type 2 DM. After adjustment for confounding factors (age, study year, body mass index, systolic blood pressure, education, occupational, commuting and leisure-time physical activity, alcohol and tea consumption, and smoking), the HRs of DM associated with the amount of coffee consumed daily (0-2, 3-4, 5-6, 7-9, > or =10 cups) were 1.00, 0.71 (95% confidence interval [CI], 0.48-1.05), 0.39 (95% CI, 0.25-0.60), 0.39 (95% CI, 0.20-0.74), and 0.21 (95% CI, 0.06-0.69) (P for trend<.001) in women, and 1.00, 0.73 (95% CI, 0.47-1.13), 0.70 (95% CI, 0.45-1.05), 0.67 (95% CI, 0.40-1.12), and 0.45 (95% CI, 0.25-0.81) (P for trend =.12) in men, respectively. In both sexes combined, the multivariate-adjusted inverse association was significant (P for trend <.001) and persisted when stratified by younger and older than 50 years; smokers and never smokers; healthy weight, overweight, and obese participants; alcohol drinker and nondrinker; and participants drinking filtered and nonfiltered coffee. CONCLUSION: Coffee drinking has a graded inverse association with the risk of type 2 DM; however, the reasons for this risk reduction associated with coffee remain unclear.

Coffee acutely modifies gastrointestinal hormone secretion and glucose tolerance in humans: glycemic effects of chlorogenic acid and caffeine. Johnston KL, Clifford MN, Morgan LM.  Am J Clin Nutr. 2003 Oct;78(4):728-33.

Centre for Nutrition and Food Safety, School of Biomedical and Molecular Sciences, University of Surrey, Guildford, UK.

BACKGROUND: Accumulating evidence suggests that certain dietary polyphenols have biological effects in the small intestine that alter the pattern of glucose uptake. Their effects, however, on glucose tolerance in humans are unknown. OBJECTIVE: The objective was to investigate whether chlorogenic acids in coffee modulate glucose uptake and gastrointestinal hormone and insulin secretion in humans. DESIGN: In a 3-way, randomized, crossover study, 9 healthy fasted volunteers consumed 25 g glucose in either 400 mL water (control) or 400 mL caffeinated or decaffeinated coffee (equivalent to 2.5 mmol chlorogenic acid/L). Blood samples were taken frequently over the following 3 h. RESULTS: Glucose and insulin concentrations tended to be higher in the first 30 min after caffeinated coffee consumption than after consumption of decaffeinated coffee or the control (P < 0.05 for total and incremental area under the curve for glucose and insulin). Glucose-dependent insulinotropic polypeptide secretion decreased throughout the experimental period (P < 0.005), and glucagon-like peptide 1 secretion increased 0-120 min postprandially (P < 0.01) after decaffeinated coffee consumption compared with the control. Glucose and insulin profiles were consistent with the known metabolic effects of caffeine. However, the gastrointestinal hormone profiles were consistent with delayed intestinal glucose absorption. CONCLUSIONS: Differences in plasma glucose, insulin, and gastrointestinal hormone profiles further confirm the potent biological action of caffeine and suggest that chlorogenic acid might have an antagonistic effect on glucose transport. Therefore, a novel function of some dietary phenols in humans may be to attenuate intestinal glucose absorption rates and shift the site of glucose absorption to more distal parts of the intestine.