title: Coffee and green tea consumption is associated with insulin resistance in Japanese adults.
abstract: OBJECTIVE
  Higher coffee and green tea consumption has been suggested to decrease risk of type 2 diabetes, but their roles in insulin resistance (IR) and insulin secretion remain unclear. This study examined the association between habitual consumption of these beverages and markers of glucose metabolism in a Japanese working population.
  
  
  METHODS
  Participants were 1440 Japanese employees (1151 men and 289 women) aged 18-69years. Consumption of coffee and green tea was ascertained via a validated brief diet history questionnaire. Multilevel linear regression was used to estimate means (95% confidence intervals) of fasting insulin, fasting plasma glucose, homeostatic model assessment of IR (HOMA-IR), homeostatic model assessment of β-cell function (HOMA-β) and glycated hemoglobin (HbA1c) with adjustment for potential confounding variables.
  
  
  RESULTS
  Coffee consumption was significantly, inversely associated with HOMA-IR (P for trend=0.03), and the association appeared to be confined to overweight subjects (BMI≥25kg/m(2)) (P for trend=0.01, P for interaction=0.08). Unexpectedly, green tea consumption was positively associated with HOMA-IR (P for trend=0.02), though there was no dose-response relationship among daily consumers of green tea. Neither coffee nor green tea consumption was associated with HOMA-β and HbA1c.
  
  
  CONCLUSIONS
  Our findings indicate that coffee consumption may be associated with decreased IR, but not with insulin secretion. The positive association between green tea consumption and IR warrants further investigation.
authors.affiliation: Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan. Electronic address: minh.pn@tnu.edu.vn.
authors.forename: Ngoc Minh
authors.initials: NM
authors.lastname: Pham
authors.affiliation: Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Nanri
authors.affiliation: Department of Health Administration, Furukawa Electric Corporation, Tokyo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kochi
authors.affiliation: Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kuwahara
authors.affiliation: Department of Health Administration, Furukawa Electric Corporation, Tokyo, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tsuruoka
authors.affiliation: Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
authors.forename: Kayo
authors.initials: K
authors.lastname: Kurotani
authors.affiliation: Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
authors.forename: Shamima
authors.initials: S
authors.lastname: Akter
authors.affiliation: Department of Health Administration, Furukawa Electric Corporation, Tokyo, Japan.
authors.forename: Isamu
authors.initials: I
authors.lastname: Kabe
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Sato
authors.affiliation: Graduate School of Nutrition and Health Science, Fukuoka Women's University, Fukuoka, Japan.
authors.forename: Hitomi
authors.initials: H
authors.lastname: Hayabuchi
authors.affiliation: Department of Epidemiology and Prevention, Center for Clinical Sciences, National Center for Global Health and Medicine, Tokyo, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mizoue
mesh_terms: D000328:Adult; D044466:Asian People; D001628:Beverages; D015415:Biomarkers / Q000097:blood / Q000378:metabolism; D001786:Blood Glucose / Q000502:physiology*; D003069:Coffee; D003430:Cross-Sectional Studies; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood* / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D050417:Insulin-Secreting Cells / Q000378:metabolism / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011795:Surveys and Questionnaires; D013662:Tea
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D003069:Coffee; D006442:Glycated Hemoglobin; D007328:Insulin; D013662:Tea
keywords: Beverage; Diabetes; Glucose metabolism; Japanese