title: Circulating irisin levels are not affected by coffee intake: a randomized controlled trial.
abstract: Irisin, secreted by skeletal muscle and possibly fat, is hypothesized to play an important role in modulating energy expenditure, obesity and metabolism. Coffee consumption also increases energy expenditure and leads to positive metabolic effects, but whether these effects are mediated by irisin remains unknown. The objective of this study was to determine the association between baseline irisin levels and the metabolic profile in humans and to investigate whether consumption of caffeinated coffee alters irisin levels. To this end, a secondary analysis was performed investigating irisin levels at baseline and after eight weeks in 32 healthy, overweight coffee drinkers who were randomized to consumption of 5 cups per day of instant caffeinated coffee, decaffeinated coffee, or water. Spearman correlation and analysis of covariance analyses were performed to identify possible associations. Irisin levels were positively correlated with waist circumference (r = 0.41, p = 0.02), fat mass (r = 0.44, p = 0.01) and CRP (r = 0.47, p = 0.007). Though there was a trend towards increased levels of irisin over time in the caffeinated coffee group (+1.8%) when compared to the placebo group (24%) this did not reach statistical significance (p = 0.75 for the trend). This first randomized trial failed to reveal any effects of coffee consumption on irisin levels, but a larger trial, appropriately sized on the basis of data provided by this study, is needed to conclusively investigate such a relationship.
  
  
  BACKGROUND
  Clinicaltrials.gov NCT00305097.
authors.affiliation: Department of Internal Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Patricia R
authors.initials: PR
authors.lastname: Peter
authors.affiliation: Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America; Department of Family Medicine, Hallym University Sacred Heart Hospital, Hallym University, Gyeonggi-do, Korea.
authors.forename: Kyung Hee
authors.initials: KH
authors.lastname: Park
authors.affiliation: Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Joo Young
authors.initials: JY
authors.lastname: Huh
authors.affiliation: Division of Preventive and Behavioral Medicine, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Wedick
authors.affiliation: Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America; Section of Endocrinology, Boston VA Healthcare System, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Christos S
authors.initials: CS
authors.lastname: Mantzoros
mesh_terms: D000328:Adult; D000886:Anthropometry; D015415:Biomarkers / Q000097:blood; D003069:Coffee; D004327:Drinking Behavior; D005260:Female; D005353:Fibronectins / Q000097:blood*; D006801:Humans; D008297:Male
chemical_list: D015415:Biomarkers; D003069:Coffee; C577593:FNDC5 protein, human; D005353:Fibronectins
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