Effect of bilberry ingestion on biomarkers of health and antioxidant content : a study of antioxidant bioavailability and acute post-ingestion effects in a controlled human intervention trial

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Effect of bilberry ingestion on biomarkers of health and antioxidant content : a study of antioxidant bioavailability and acute post-ingestion effects in a controlled human intervention trial


Author: Li, Sze-wai
Title: Effect of bilberry ingestion on biomarkers of health and antioxidant content : a study of antioxidant bioavailability and acute post-ingestion effects in a controlled human intervention trial
Degree: M.Sc.
Year: 2008
Subject: Hong Kong Polytechnic University -- Dissertations.
Bilberry -- Therapeutic use.
Biochemical markers.
Department: Dept. of Health Technology and Informatics
Pages: xi, 107 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2305601
URI: http://theses.lib.polyu.edu.hk/handle/200/3697
Abstract: Bilberries (Vacciniwn Myrtillus) have been reported to be beneficial to health because of their high antioxidant activity attributable to anthocyanins and other polyphenolic compounds. These reputed health effects include anti-cancer, antioxidant, anti-ulcer, anti-aging, eye vision improvement, effects of cerebrovascular and neuroprotection. However, recent findings have not reached a consensus and some are based on animals, cell culture and epidemiological studies only. In order to evaluate the health benefits of anthocyanins in humans, the bioavailability i.e. the way of absorption, distribution, excretion and how they are metabolized must be known. The use of bilberry supplementation as a 'functional food' to treat or prevent cerebrovascular disease (CVD) is likely to have most benefit in high risk populations, such as Type 2 diabetic subjects. So the aims of this study were to investigate the potential health effects of bilberries via (1) in vitro study of a number of commercial bilberry products (2) in vivo study of bioavailability of bilberry antioxidants. The first part of this study was to conduct a preliminary in vitro testing on bilberry's antioxidant properties. Commercial bilberry products were evaluated on their content of anthocyanins, total polyphenols and total antioxidant power (as the Ferric reducing / Antioxidant Power (FRAP) in freshly prepared room temperature water, 75 oC water and ethanolic extracts of 0.5% w/v. Different methodologies would also be explored and provided the basis information for the later in vivo study. Here the pH differential colorimetric method was adopted for measuring the concentration of anthocyanins in bilberry products. As far as I know, the test was not tested and assessed before in this course of The Hong Kong Polytechnic University. The results were then correlated with FRAP values to help guide the choice of supplement in later in vivo study. The preliminary in vitro study showed that bilberries possessed antioxidative power and there was a wide variation of anthocyanin levels among the commercial products (from below 1 to 300 mg/g of powder). The pH differential colorimetric method for anthocyanins was simple and fast for measuring total anthocyanins in fruits, powdered bilberry extracts and juice. Precision for anthocyanin was also good: one bilberry extract containing ~ 13.5 mg /g of powder was chosen for testing. The within run coefficient of variation were 4.02% (n = 5), between run (between day) coefficient of variation were 4.13% (n = 5). In the in vivo bioavailability study, the post acute-ingestion effects were assessed in a single-blinded, placebo-controlled human intervention trial of cross-over design. It was intended to investigate the effect of supplementation with bilberries on plasma and urine antioxidant status. Fasting blood, urine were collected from 8 apparently healthy persons (n =8). Repeated fasting samples were collected at different time points after either bilberry (~2.4g) or water ingestion. The whole procedure was repeated one week later to allow a sufficient wash out period. Results showed that there was a statistically significant increase of excreted urine polyphenols at peak 120 minutes post-ingestion in the subjects who had ingested bilberry extracts instead of water (p< 0.001, by repeated measures analysis of variance test). When corresponding pairs were compared, higher values of excreted polyphenols at all time points post-ingestion were shown in subjects who had ingested bilberry, which were significantly different from those who ingested water only (p< 0.008, by Mann-Whitney U test). However, there was no statistically increase of plasma FRAP after bilberry supplementation. One main drawback of the study was we did not know how much excreted polyphenols were actually ingested dietary anthocyanins of bilberry. Urine samples tended to form fog in low pH when we tried to measure its content of anthocyanins by the pH differential colorimetric method. Other types of polyphenolic compounds might have been added in the original bilberry extracts that contributed to the observed increase of excreted polyphenols. Apparently, a HPLC method may be helpful to resolve the problem. Although no increased peak of plasma antioxidative power was observed after bilberry ingestion, the plasma FRAP level seemed to be maintained at a relatively higher level than just water intake. It was reasonably to think that exogenous dietary antioxidants helped to maintain the body antioxidative status better than those people who only ingested water which started to use up their own reserve. In conclusion, there is evidence that dietary bilberry antioxidants are absorbed and excreted; a follow up supplementation trial looking at health effects of bilberry is justified.

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