title: A 6-month randomized pilot study of black tea and cardiovascular risk factors.
abstract: BACKGROUND
  The effects of black tea consumption on cardiovascular risk factors have been inconsistent in previous randomized trials, all of which have been limited to a few weeks duration.
  
  
  METHODS
  We conducted a pilot parallel-design randomized controlled trial among 31 adults aged 55 years and older with either diabetes or 2 other cardiovascular risk factors but no established clinical cardiovascular disease. Participants were randomized to drink 3 glasses daily of either a standardized black tea preparation or water for 6 months. Cardiovascular risk factors were measured at the beginning and conclusion of the study.
  
  
  RESULTS
  Three participants dropped out of the study, leaving 14 participants assigned to tea and 14 assigned to water eligible for analyses. We found no statistically significant effects of black tea on cardiovascular biomarkers, including lipids, inflammatory markers, hemoglobin, adhesion molecules, prothrombotic and fibrinolytic parameters, and lipoprotein oxidizability. Assignment to tea did not appreciably influence blood pressure, and heart rate among participants assigned to tea was marginally higher than among control participants at 3 months (P = .07) but not 6 months.
  
  
  CONCLUSIONS
  In this randomized trial of black tea intake over 6 months among older adults with known cardiovascular risk factors, black tea did not appreciably influence any traditional or novel biomarkers of cardiovascular risk. Longer randomized trials are needed to verify the inverse association of tea with risk of cardiovascular disease seen in cohort studies and identify potential candidate mechanisms for such an association.
authors: Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02446, USA. kmukamal@bidmc.harvard.edu
authors: Kenneth J
authors: KJ
authors: Mukamal
authors: Kristen
authors: K
authors: MacDermott
authors: Joe A
authors: JA
authors: Vinson
authors: Noriko
authors: N
authors: Oyama
authors: Warren J
authors: WJ
authors: Manning
authors: Murray A
authors: MA
authors: Mittleman
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D002318:Cardiovascular Diseases / Q000097:blood* / Q000453:epidemiology*; D003920:Diabetes Mellitus / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D012307:Risk Factors; D013662:Tea
chemical_list: D015415:Biomarkers; D013662:Tea