To study the main and interactive effects of green tea and vitamin C on selected biomarkers of cardiovascular disease risk

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To study the main and interactive effects of green tea and vitamin C on selected biomarkers of cardiovascular disease risk

 

Author: Chan, Koon-cheong Martin
Title: To study the main and interactive effects of green tea and vitamin C on selected biomarkers of cardiovascular disease risk
Degree: M.Sc.
Year: 2006
Subject: Hong Kong Polytechnic University -- Dissertations.
Green tea -- Health aspects.
Vitamin C -- Therapeutic use.
Antioxidants.
Cardiovascular system -- Diseases -- Nutritional aspects.
Department: Dept. of Health Technology and Informatics
Pages: xi, 73 leaves : ill. ; 31 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2090267
URI: http://theses.lib.polyu.edu.hk/handle/200/169
Abstract: As green tea is the second most popular beverage and vitamin C is an important dietary derived antioxidant, high intake of vitamin C (ascorbic acid) and green tea (rich in polyphenolic antioxidants such as epigallocatechin gallate [EGCG]) are reported to lower the risk of a variety of age-related diseases, including cardiovascular disease (CVD). Therefore, the aim of this study was to investigate the main and interactive effects of green tea and vitamin C on selected biomarkers of cardiovascular disease risk. Specific questions to be addressed included: 1. Is there a significant change in biomarkers of CVD risk after 4 weeks' supplementation with vitamin C, green tea or both? 2. Is there evidence of a synergistic or co-operative interaction between vitamin C and green tea when these are taken in combination? The study was a randomized, placebo-controlled, single-blinded study of modified balanced incomplete block design. Thirty-two healthy Chinese non-smoking subjects, aged 30-55 years were recruited. Selected biomarkers of CVD risk were measured in blood samples collected before and after 4 weeks' daily supplementation with green tea, vitamin C, both or neither (total n=16 for each treatment). There was a 6 week washout period. After the washout period, subjects were allocated to another treatment for the next 4 weeks. The biomarkers measured included fasting plasma total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, uric acid, homocysteine, hs-CRP, as well as the waist-to-hip ratio, systolic pressure and diastolic pressure. These were all measured before and after each 4-week treatment period. Results were analysed by using Graphpad Prism (version 4.0, San Diego, USA). The differences in the change of the biomarkers within each supplementation groups during 4 weeks' supplementation were investigated by using Student's t test for paired data. The mean differences of change of biomarkers between supplementation groups were investigated by using Student's t test for unpaired data and significance was sought at the 5 % level. Results showed no significant differences in the baseline characteristics or in the baseline levels of biomarkers of CVD risk between the four groups. Four weeks' treatment with 500 ml per day of 0.8% w/v green tea infusion was associated with a significant (p<0.05) decrease in plasma uric acid concentration (Mean+-SD: -30+-4 umol/L). Treatment with 500 mg/d vitamin C for 4 weeks was associated with a significant (p<0.05) decrease in both plasma total cholesterol (-0.17+-0.29 mmol/L) and LDL-cholesterol (-0.14+-0.19 mmol/L). In addition, this was associated with a significant (p<0.05) increase in plasma homocysteine (0.82+-0.93 umol/L) and significant increase in waist to hip ratio (0.01+-0.02). Treatment with 500 mg/d vitamin C plus 500ml per day of 0.8% w/v green tea infusion for 28 days was not associated with any significant (p<0.05) changes in the level of measured biomarkers of CVD risk. In comparing those who took vitamin C (alone or with tea, n=32), results showed that there was significant (p<0.05) decrease in plasma total cholesterol (-0.17 +-0.39 mmol/L) with vitamin C. Also, there was significant (p<0.05) decrease in waist to hip ratio (-0.01 +-.03) in the group receiving green tea when compared with the group without green tea (n=32 for both groups). In conclusion, while changes in the healthy subjects studied were small, supplementation with vitamin C and green tea showed statistically significant effects on biomarkers of cardiovascular disease. Increased intake of dietary antioxidants in green tea can cause significant reduction in plasma uric acid and the waist to hip ratio. Also, the intake of vitamin C can lower the cholesterol concentration significantly. In addition, there is a co-operative effect of taking green tea and vitamin C together in decreasing the plasma homocysteine significantly. So, these pilot experimental data can contribute to future study investigating the effect of green tea and vitamin C in the prevention of cardiovascular and other age-related disease.

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