Associations between the intake of caffeinated and decaffeinated coffee and measures of insulin sensitivity and beta cell function.
OBJECTIVE
Although protective relationships between coffee consumption and type 2 diabetes mellitus have consistently been observed, few studies have examined the relationships between coffee consumption and underlying pathophysiological defects that characterise diabetes aetiology. The aim of this study was to explore the associations between caffeinated and decaffeinated coffee consumption and measures of insulin sensitivity and secretion.


METHODS
The study population included 954 multi-ethnic non-diabetic adults from the Insulin Resistance Atherosclerosis Study (IRAS). Multiple regression analyses were performed to examine the cross-sectional relationships between caffeinated and decaffeinated coffee intake and insulin sensitivity and acute insulin response, measured by a frequently sampled intravenous glucose tolerance test, 2 h postload glucose measured by OGTT, fasting insulin, and proinsulin to C-peptide ratios.


RESULTS
Caffeinated coffee intake was positively associated with insulin sensitivity (β = 0.054; SE = 0.026; p = 0.04) and inversely related to 2 h postload glucose (β = -0.37; SE = 0.10; p = 0.0003) in fully adjusted models. Caffeinated coffee intake was not associated with acute insulin response or proinsulin ratios. Decaffeinated coffee intake was inversely related to 2 h postload glucose (β = -0.47; SE = 0.18; p = 0.0096) and positively related to acute insulin response (β = 0.191; SE = 0.077; p = 0.0132). Decaffeinated coffee intake was inversely related to the ratios of both intact and split proinsulin to C-peptide (β = -0.150; SE = 0.061; p = 0.0148; β = -0.254; SE = 0.068; p = 0.0002, respectively).


CONCLUSIONS
In this cross-sectional study, caffeinated coffee was positively related to insulin sensitivity and decaffeinated coffee was favourably related to measures of beta cell function. These results provide pathophysiological insight as to how coffee could impact the risk of type 2 diabetes mellitus.
Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, FitzGerald Building, 150 College St, Toronto, ON, Canada.
R C
RC
Loopstra-Masters
A D
AD
Liese
S M
SM
Haffner
L E
LE
Wagenknecht
A J
AJ
Hanley
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000502:physiology; D002110:Caffeine; D003069:Coffee; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012044:Regression Analysis; D011795:Surveys and Questionnaires
D001786:Blood Glucose; D003069:Coffee; D002110:Caffeine