Effect of green tea and ascorbic acid consumption on iron status, inflammation and thrombotic index : implications for modulating risk of cardiovascular disease

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Effect of green tea and ascorbic acid consumption on iron status, inflammation and thrombotic index : implications for modulating risk of cardiovascular disease


Author: Mak, Lai-yee Karen
Title: Effect of green tea and ascorbic acid consumption on iron status, inflammation and thrombotic index : implications for modulating risk of cardiovascular disease
Degree: M.Sc.
Year: 2006
Subject: Hong Kong Polytechnic University -- Dissertations.
Cardiovascular system -- Diseases -- Treatment.
Green tea -- Therapeutic use.
Department: Dept. of Health Technology and Informatics
Pages: x, 120 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2174235
URI: http://theses.lib.polyu.edu.hk/handle/200/2147
Abstract: Atherosclerosis is considered as a dynamic progressive disease arising from the combination of endothelial dysfunction, inflammation and increased oxidative stress, and resulting in an acute thrombotic event such as a myocardial infarction. In principle, decreasing oxidative stress and associated inflammation should have a beneficial effect in preventing or inhibiting development of cardiovascular disease (CVD). In observational studies increased intake and plasma levels of ascorbic acid are associated with lower risk of CVD. However, intervention studies with vitamin C have shown no change in markers of oxidation nor shown clear clinical benefit. Epidemiologic evidence regarding the effects of tea consumption on cardiovascular disease risk is conflicting. Besides, many epidemiological studies suggest a link between abnormal iron storage and the development of atherosclerosis. Ascorbic acid was reported to enhance absorption of non-haem iron while polyphenols had an inhibitory effect. It would be interesting to investigate the combined effect of these dietary antioxidants on iron status. In this human supplementation trial, inflammation markers (hsCRP, white cell count, VCAM-1), thrombotic markers (fibrinogen, factor VII), haemoglobin and ferritin were employed to investigate the main and interactive effects of vitamin C and green tea consumption in a randomized, placebo-controlled, blinded study of modified balanced incomplete block design. Thirty-two apparently healthy volunteers aged 30-55 years were recruited. Each received two 4-week treatments with either 500ml 0.8%w/v green tea, 500mg vitamin C, both or neither, with a six-week washout period between treatments. Results showed a significant increase in ascorbic acid (p<0.004) in males after vitamin C supplementation. Interestingly, the increase of ascorbic acid was non-significant in female participants. There was also a significant decrease of white cell count in male participants taking vitamin C (p=0.0008). This group of well-nourished females seemed to be non-responders to vitamin C treatment. In women, but not men, a significant decrease in white cell count (p=0.006) after 28days green tea supplementation was seen. Interestingly, ferritin increased significantly in males after green tea supplementation (p=0.0007). There was no evidence of synergistic effect of green tea and vitamin C, and no sparing effect of vitamin C was found in the combined treatment. In correlational study, plasma ascorbic acid was inversely correlated (p<0.05) with ferritin. This negative association provides supportive evidence for the hypothesis that increased ascorbic acid is related to lower level of inflammation markers and therefore lower risk of CVD. Although no significant differences were observed in other inflammation and thrombotic markers after vitamin C and/or green tea supplementation, this is one of the first human intervention trials that have employed these markers. The study has shown some evidence of CVD benefit in green tea or ascorbic acid consumption. A wider inflammation marker profile is suggested for follow-up study to validate this finding.

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