title: Simultaneous ingestion of dietary proteins reduces the bioavailability of galloylated catechins from green tea in humans.
abstract: OBJECTIVE
  To investigate the influence of dietary proteins (casein, soy protein) and skimmed milk on the plasma kinetics of green tea (GT) catechins.
  
  
  METHODS
  In a randomized cross-over design with one-week intervals, 24 healthy normal-weight women consumed a test drink containing 1.75 g GT extract with or without the addition of different proteins. Treatments were GT (control), GT with skimmed milk (GT + M), GT with caseinate (GT + CS), or GT with soy protein (GT + S). Venous blood samples were taken before and several times during a period of 4.5 h after consumption of the test drink. Plasma concentrations of catechins were analyzed by HPLC with electrochemical detection.
  
  
  RESULTS
  Compared to control, consumption of GT with milk, caseinate, or soy protein significantly reduced the bioavailability (mean area under the plasma concentration-time curve) of total catechins (means ± SEM; GT + M, 87 ± 5%; GT + CS, 79 ± 5%; GT + S, 88 ± 4%), epigallocatechin gallate (GT + M, 68 ± 4%; GT + CS, 63 ± 5%; GT + S, 76 ± 5%), and epicatechin gallate (GT + M, 68 ± 5%; GT + CS, 66 ± 6%; GT + S, 77 ± 6%), while the bioavailability of non-galloylated catechins such as epigallocatechin (GT + M, 134 ± 9%; GT + CS, 118 ± 9 %; GT + S, 123 ± 8%) and epicatechin (GT + M, 125 ± 10%; GT + CS, 114 ± 11%; GT + S, 110 ± 8%) significantly increased. No significant differences in bioavailability of GT catechins were observed between the treatments GT + M, GT + CS, or GT + S.
  
  
  CONCLUSIONS
  Simultaneous ingestion of dietary proteins reduces the bioavailability of galloylated catechins from GT in humans.
authors.affiliation: Department of Nutrition and Food Science, Nutritional Physiology, University of Bonn, Endenicher Allee 11-13, 53115, Bonn, Germany. s.egert@uni-bonn.de
authors.forename: Sarah
authors.initials: S
authors.lastname: Egert
authors.forename: Jane
authors.initials: J
authors.lastname: Tereszczuk
authors.forename: Silvia
authors.initials: S
authors.lastname: Wein
authors.forename: Manfred James
authors.initials: MJ
authors.lastname: Müller
authors.forename: Jan
authors.initials: J
authors.lastname: Frank
authors.forename: Gerald
authors.initials: G
authors.lastname: Rimbach
authors.forename: Siegfried
authors.initials: S
authors.lastname: Wolffram
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001682:Biological Availability; D015992:Body Mass Index; D002392:Catechin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D002851:Chromatography, High Pressure Liquid; D018592:Cross-Over Studies; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D011795:Surveys and Questionnaires; D013662:Tea / Q000737:chemistry*; D055815:Young Adult
chemical_list: D000975:Antioxidants; D004044:Dietary Proteins; D013662:Tea; D002392:Catechin; C062669:epicatechin gallate; C045651:epigallocatechin gallate; C057580:gallocatechol