The effects of acute garlic supplementation on the fibrinolytic and vasoreactive response to exercise

Background: The purpose of this project was to examine the effects of acute garlic supplementation on fibrinolysis and vasoreactivity both at rest and following maximal exercise. Methods: Eighteen healthy trained males (20.9 +/- 2.2 years, 178 +/- 7.7 cm, 75.5 +/- 9.6 kg, VO(2)max = 59.8 +/- 6.7 ml.kg(-1).min(-1)) performed a graded treadmill test to volitional exhaustion. Blood samples were taken at rest, within two minutes post-exercise, and one hour post-exercise. Eleven of the subjects also had a brachial vasoreactivity test performed immediately after the blood sample to assess flow-mediated dilation (FMD) of the brachial artery. Participants were randomly assigned to ingest either 900 mg of powdered garlic or a placebo three hours before the exercise session. The supplement was distributed in a double-blind, crossover fashion. Participants repeated the protocol with the other treatment after a 14-day washout period. Paired t-tests were used to compare VO(2)max between the two trials. A two-factor (treatment and time) repeated measures analysis of variance (ANOVA) was used to assess changes in FMD, tPA activity, tPA antigen, and PAI-1 activity. A priori statistical significance was set at P < 0.05. Results: VO(2)max was greater for the garlic treatment trial vs. placebo (Placebo = 59.8 +/- 6.7 ml.kg(-1).min(-1); Garlic = 61.4 +/- 6.6 ml.kg(-1).min(-1)). There was no main effect for treatment and no treatment x time interaction for FMD or any fibrinolytic variables examined. Conclusion: Acute garlic supplementation does not alter vasoreactivity, fibrinolytic potential or the fibrinolytic response to exercise in young healthy trained males. Acute garlic supplementation does, however, cause a small but statistically significant increase in VO(2)max. It remains unclear if this increase in VO(2)max is of functional importance.