| Author: | Leung, Wai-yuen Jason |
| Title: | Main and interactive effects of green tea and vitamin C on biomarkers of oxidant : antioxidant balance and the implication for healthy ageing |
| Degree: | M.Sc. |
| Year: | 2006 |
| Subject: | Hong Kong Polytechnic University -- Dissertations. Green tea -- Health aspects. Vitamin C -- Health aspects. Aging -- Nutritional aspects. Antioxidants -- Physiological effect. |
| Department: | Department of Health Technology and Informatics |
| Pages: | xiv, 177 leaves : ill. (some col.) ; 30 cm. |
| Language: | English |
| Abstract: | Researchers try to find the way to promote healthy ageing and functional longevity so as to lighten the medical expense burden on the society and improve quality of life for our elders. Green tea is rich in flavonoid antioxidants and vitamin C is the major water soluble dietary derived antioxidant. Although, the effects of green tea and vitamin C intake on the age-related diseases have been studied and widely published, information of interaction effect of antioxidant is seldom found. This study investigated the main and interactive effects of green tea and vitamin C on biomarkers of oxidant: antioxidant balance in a human supplementation intervention trial. The study design was a randomized, placebo-controlled, single-blinded study, of modified balanced incomplete block design. A total of 32 apparently healthy subjects (30-60 years old, and approximately equal numbers of men and women) were recruited with their informed consent. A supplementation treatment of green tea (500ml/day of 0.8%w/v tea infusion), vitamin C (500mg/day), both or neither was assigned to each subjects (n = 8 in each treatment group). The treatment lasted for 4 weeks. There was a 6-week washout period, after which subjects were each allocated to one of the other treatment for another 4 weeks. Fasting blood and urine sample were collected before and after each 4 weeks' daily supplementation. The focus of this study was on biomarkers of antioxidant status, including plasma MDA, allantoin, FRAP, ascorbic acid, a-tocopherol, and erythrocyte SOD activity and GPx activity. Results showed that the 4-weeks supplementation with vitamin C only (n = 16) did not give any statistically significant change in oxidative stress status of the subjects with respect to the biomarkers measured, although a small non-significant decrease was observed in plasma MDA (mean -0.2%) and plasma allantoin (mean -2.3%). For the biomarkers of antioxidant defence, there was a statistically significant increase in plasma ascorbic acid (mean +20.7%; PO.05) with vitamin C supplementation. Small, non-significant increases were seen plasma FRAP (mean +2.9%), GPx activity (mean +1.4%) and SOD activity (mean +2.9%) with vitamin C supplementation. For those taking green tea only (n = 16), the results did not show any statistically significant response on the biomarkers of oxidative stress but different responses for the biomarkers of antioxidant defence were obtained. There was a significant decrease in plasma FRAP (mean -5.2%; PO.05) and a significant increase in SOD activity (mean +6.1%; PO.05) for those taking green tea only (n = 16) and, in factorial analysis, in GPx activity (mean -4.0%; PO.05) for those taking green tea (n = 32). Results also suggested sex-differences in response to vitamin C supplemention in regard to plasma allantoin and GPx activity, however groups were small (females (n = 6) and males (n = 10)). No co-operative or synergistic interaction between vitamin C and green tea when they were taken in combination was observed with respect to plasma ascorbic acid. There was a suggestion of an additive or synergistic effect on plasma MDA (subjects with vitamin C only: mean -0.2%; subjects with vitamin C with green tea: mean -2.7%) and plasma allantoin (subjects with vitamin C only: mean -2.3%; subjects with vitamin C with green tea: mean -4.6%). Moreover, a trend in counter-effect on plasma FRAP was illustrated (all subjects with vitamin C only: mean +2.9%; subjects with vitamin C with green tea: mean +1.0%). Possible interaction between vitamin C and green tea remains to be confirmed in future study. The results of all biomarkers tested in the present study demonstrated moderately strong direct correlations such as plasma MDA against plasma allantoin (r = 0.436; P = 0.013), GPx activity against plasma MDA (r = 0.618; P = 0.0002) and plasma allantoin (r = 0.511; P = 0.003) and a weaker direct correlation between plasma allantoin and plasma FRAP (r = 0.313; P = 0.081). In conclusion, the findings of the present study suggest the beneficial effect of "vitamin C" supplement on the biomarkers with respect to oxidant: antioxidant balance shifting the balance towards to antioxidant defence side. Furthermore, the result did not show any evidence of a pro-oxidant effect of vitamin C in vivo. Green tea supplement favours the biomarkers of antioxidant defence side. The interaction between green tea and vitamin C cannot be excluded and remains to be confirmed in future study. New and interesting direct correlations were demonstrated among the biomarkers of oxidative stress and antioxidant defence. |
| Rights: | All rights reserved |
| Access: | restricted access |
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| File | Description | Size | Format | |
|---|---|---|---|---|
| b21742327.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 40.23 MB | Adobe PDF | View/Open |
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