Tea drinking and haemostasis: a randomized, placebo-controlled, crossover study in free-living subjects.
The hypothesis that tea drinking may protect against coronary heart disease (CHD) through effects on clotting as measured by plasma fibrinogen, tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) was tested in 65 healthy volunteers (31 men and 34 women; aged 20-74 years) in a randomized, blind, placebo-controlled, crossover study lasting 10 weeks (run-in phase 2 weeks, tea and placebo phases 4 weeks). During the placebo phase, intakes of milk, sugar, water and caffeine were matched to those in the tea phase during which 6 mugs of tea were drunk daily. Compliance with tea intake was measured by marking tea bags with p-aminobenzoic acid and measuring recovery in 24-hour urine collections. The mean +/- SD fibrinogen level, PAI-1 activity and tPA antigen level at baseline of 2.91 +/- 0.81 g/l, 7.9 +/- 5.3 U/ml and 4.76 +/- 2.17 ng/ml, respectively, were in the normal range. No significant differences in these variables between the run-in, tea or placebo phases were observed. The putative protective effect of tea against development of CHD is not mediated through effects of black tea on fibrinogen, tPA or PAI-1.
Vorster
H
H
Department of Nutrition, Potchefstroom University for Christian Higher Education, Potchefstroom, South Africa.
Jerling
J
J
Oosthuizen
W
W
Cummings
J
J
Bingham
S
S
Magee
L
L
Mulligan
A
A
Runswick
S
S
D000328:Adult; D000368:Aged; D003327:Coronary Disease / Q000209:etiology*; D018592:Cross-Over Studies; D004326:Drinking / Q000502:physiology*; D005260:Female; D005340:Fibrinogen / Q000378:metabolism*; D005342:Fibrinolysis / Q000502:physiology*; D006487:Hemostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D010919:Placebos; D012016:Reference Values; D012307:Risk Factors; D013662:Tea
D010919:Placebos; D013662:Tea; D005340:Fibrinogen