A Study of the effects of Antioxidants and Caffeine in Tea on Cardiovascular Parameters and Cognitive Function
(2015) A Study of the effects of Antioxidants and Caffeine in Tea on Cardiovascular Parameters and Cognitive Function, no. 44.
Introduction: Tea is one of the most highly consumed beverages worldwide. Recently there has been increasing evidence that both green and black teas are beneficial for cardiovascular health and cognitive function. However studies have not focused on the effect of a variety of teas with different antioxidant and caffeine levels after just one cup consumed, where it is of interest if any have an effect on cardiovascular parameter or cognitive function. Aim: The aim of the study was to investigate the effects of two green and two black teas which contained different amounts of antioxidants and caffeine and to assess each tea's effect on cognitive function and cardiovascular parameters after just one cup consumed. Materials and Methods: The study involved the recruitment of 11 healthy university students who were measured at baseline for cardiovascular parameters and cognitive function. Participants returned on four different occasions to receive four teas - Scottish breakfast (46.8mg caffeine, 1020μmol antioxidants), decaffeinated breakfast (0mg caffeine, 1230μmol antioxidants), jasmine chun hao (36.3mg caffeine, 2619 μmol antioxidants) and gyokuro (31.38mg, 1547μmol antioxidants) and returned for the same cardiovascular parameters and cognitive function tests one hour after consumption. The study was randomised and single blinded. Results: Blood pressure decreased after the consumption of jasmine chun hao (p=0.018) and gyokuro (p=0.05). Increases in augmentation index (p=0.03) and heart rate (P=0.03) were seen after gyokuro ingestion but not with other teas consumed. Digit span length increased after Scottish breakfast (p=0.001), decaffeinated breakfast (p=0.0003), jasmine chun hao (p=0.002) and gyokuro (p=0.038). Corsi block sequence length only increased with Scottish breakfast (p=0.03) and improved changes in stroop testing were seen in only black tea consumption. Conclusion: The findings of the study do support previous evidence that both green and black teas are beneficial to health. Higher levels of antioxidants found in green tea are especially beneficially for blood pressure, where as black tea with higher caffeine is more effective in improving cognitive function. Key Words: Tea, caffeine, antioxidants, cognitive functions, cardiovascular parameters