title: Coffee consumption, serum γ-glutamyltransferase, and glucose tolerance status in middle-aged Japanese men.
abstract: BACKGROUND
  Recently, coffee consumption has been related to decreased risk of type 2 diabetes mellitus (DM) among those with high levels of serum γ-glutamyltransferase (GGT). We examined the association between coffee and glucose tolerance, determined by a 75 g oral glucose tolerance test, and the effect modification of serum GGT on the association.
  
  
  METHODS
  The study subjects were 5320 men aged 46-60 years who received a health examination at two Self-Defense Forces hospitals from January 1997 to March 2004. Those medicated for DM were excluded. Coffee consumption was classified into <1, 1-2, 3-4, and ≥5 cups/day. Statistical adjustment was made for age, body mass index, smoking, alcohol use, leisure-time physical activity, green tea consumption, parental diabetes, hospital, and rank in the Self-Defense Forces.
  
  
  RESULTS
  Men with normal glucose tolerance, isolated impaired fasting glucose (IFG), isolated impaired glucose tolerance (IGT), combined IFG/IGT, and type 2 DM numbered 3384, 398, 790, 348, and 400, respectively. The prevalence odds of isolated IGT, combined IFG/IGT, and type 2 DM, but not of isolated IFG, decreased with increasing consumption of coffee. An inverse association with coffee was observed for isolated IGT in both low (≤40 IU/L) and high (>40 IU/L) GGT groups, and for combined IFG/IGT and type 2 DM in the latter group.
  
  
  CONCLUSIONS
  Coffee drinking is protective against glucose intolerance. A possible effect modification of GGT on the coffee-DM association warrants further studies.
authors: Department of Preventive Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan. hiram@phealth.med.kyushu-u.ac.jp
authors: Tatsuo
authors: T
authors: Hiramatsu
authors: Osamu
authors: O
authors: Tajima
authors: Kousaku
authors: K
authors: Uezono
authors: Shinji
authors: S
authors: Tabata
authors: Hiroshi
authors: H
authors: Abe
authors: Keizo
authors: K
authors: Ohnaka
authors: Suminori
authors: S
authors: Kono
mesh_terms: D002110:Caffeine / Q000008:administration & dosage; D003069:Coffee; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000201:enzymology / Q000453:epidemiology*; D018149:Glucose Intolerance / Q000097:blood / Q000453:epidemiology*; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D011795:Surveys and Questionnaires; D005723:gamma-Glutamyltransferase / Q000097:blood*
chemical_list: D003069:Coffee; D002110:Caffeine; D005723:gamma-Glutamyltransferase