Caffeinated Coffee, Decaffeinated Coffee, and Caffeine in Relation to Plasma C-Peptide Levels, a Marker of Insulin Secretion, in U.S. Women

Abstract

OBJECTIVE -Coffee consumption is associated with reduced risk of type 2 diabetes, but the mechanism is not clearly understood. Elevated C-peptide, as a marker of insulin secretion, has been linked to insulin-resistant type 2 diabetes. In this study, we examined consumption of caffeinated and decaffeinated coffee and total caffeine in relation to concentrations of plasma C-peptide.RESEARCH DESIGN AND METHODS -Plasma C-peptide concentrations were measured in a cross-sectional setting among 2,112 healthy women from the Nurses' Health Study I who provided blood samples in 1989 -1990. Consumption of caffeinated and decaffeinated coffee and total caffeine was assessed using a semiquantitative food-frequency questionnaire in 1990.RESULTS -Intakes of caffeinated and decaffeinated coffee and caffeine in 1990 were each inversely associated with C-peptide concentration in age-adjusted, BMI-adjusted, and multivariable-adjusted analyses. In multivariable analysis, concentrations of C-peptide were 16% less in women who drank Ͼ4 cups/day of caffeinated or decaffeinated coffee compared with nondrinkers (P Ͻ 0.005 for each). Women in the highest quintile compared with the lowest quintile of caffeine intake had 10% lower C-peptide levels (P ϭ 0.02). We did not find any association between tea and C-peptide. The inverse association between caffeinated coffee and C-peptide was considerably stronger in obese (27% reduction) and overweight women (20% reduction) than in normal weight women (11% reduction) (P ϭ 0.005).CONCLUSIONS -Our findings suggest a potential reduction of insulin secretion by coffee in women. This reduction may be related to other components in coffee rather than caffeine. Diabetes Care 28:1390 -1396, 2005C offee intake has been associated with a reduction in the risk of type 2 diabetes (1-4). Because of its widespread consumption, understanding the relationship between coffee intake and insulin secretion may have implications in the prevention and treatment of diabetes.In contrast, short-term studies have consistently shown that acute administration of caffeine induces insulin resistance and impairs glucose tolerance (3,5,6). Longterm effects of caffeine and other components of coffee, which may be more relevant on insulin secretion, have been less well studied. In a recent crosssectional study of 936 elderly men without diabetes, coffee was associated with increased insulin sensitivity but not with decreased secretion (7). However, this study did not distinguish between caffeinated and decaffeinated coffee, did not study women, and measured only the early insulin response under glucose stimulation.C-peptide is cleaved from proinsulin and released into the bloodstream in equivalent amounts with insulin (8). Increased C-peptide has been associated with insulin resistance and diabetes (9), cardiovascular disease (10), and colon cancer (11). According to the National Coffee Association, 54% of adults in the U.S. drank coffee in 2000, with average per capita daily consumption of 1.9 cups for men and 1.4 cups for women...

Coffee, tea, and caffeine consumption and serum uric acid level: The third national health and nutrition examination survey

“…These findings suggest that components of coffee other than caffeine contribute to the observed inverse association between coffee intake and uric acid levels. These findings closely agree with a recent study that found that both caffeinated and decaffeinated coffee were inversely associated with C peptide levels (a marker of endogenous insulin levels), but tea intake and total caffeine intake after adjusting for coffee intake were not (7). Because there is a strong positive relationship between serum insulin resistance and hyperuricemia (23)(24)(25)(26)(27) and insulin reduces the renal excretion of urate (25,28,29), decreased insulin resistance and insulin levels associated with coffee consumption may lead to lower uric acid levels.…”

“…Coffee and tea consumption may affect serum uric acid levels via various mechanisms including influence on insulin resistance (2)(3)(4)(5)(6)(7)(8)(9), but few data are available. Only 1 cross-sectional study investigated the link between these beverages and serum uric acid level based on 2,240 Japanese men and found a significant inverse association between coffee consumption and serum uric acid levels but no association with tea consumption (10).…”

Coffee consumption is not related to the metabolic syndrome at the age of 36 years: the Amsterdam Growth and Health Longitudinal Study

“…In the literature, however, beneficial effects of coffee on glycaemic markers have been found and positive associations between coffee consumption and insulin sensitivity have been reported (Agardh et al, 2004;Arnlov et al, 2004;van Dam et al, 2004). Furthermore, coffee consumption of both caffeinated and decaffeinated coffee was associated with a decrease in C-peptide levels in women, indicating that chronic coffee consumption reduces insulin secretion (Wu et al, 2005). In our study, unfortunately, no information on insulin sensitivity or fasting glucose levels was available.…”

Putative biases in estimating mortality attributable to obesity in the US population

“…This technique has been used for predictors such as alcohol consumption, 16 coffee consumption, 17 physical activity 18 and blood pressure. 19,20 We used the average BMI at visits 1, 2 and 3.…”