Posted 10 November 2008 - 04:38 PM
Find some studies below pointing that resveratrol just isn't bioavailable enough so i think that the more you pop the more money you throw away.There are better ways to get optimal health using the money you would normally spent on resveratrol.I still see it as a big hype.
Abstract Background and Aim: Several in vitro studies have demonstrated the ability of pure trans-resveratrol (t-Res) to act as an anti-oxidant, but the scientific literature is lacking in in vivo studies dealing with dietary t-Res bioavailability in oxidative stress models. Our aim was to investigate the bioavailability of t-Res from dietary sources and its effect on an animal model of carbon tetrachloride (CCl(4))-induced liver lipid peroxidation. Methods: Ten rats were intragastrically administered for 14 days with a grape-stalk extract determining a daily t-Res dosage of 3 mg/kg. The control group (10 rats) was daily injected with the vehicle solvent without the t-Res extract. After 1 week, the induction of liver lipid peroxidation by CCl(4) injection was carried out. Serum and liver samples, at different time intervals, were collected to evaluate t-Res content, by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectometry-mass spectometry (LC-MS-MS). Liver malondialdehyde (MDA) as marker of oxidative stress was measured. Results: t-Res accumulates in the liver reaching 49.8 +/- 10.2 ng/g after 7 days and 191.8 +/- 15.3 ng/g after 14 days. No t-Res was detected in serum. The increase of MDA liver concentration due to CCl(4) injection after 24 h and 1 week was reduced by 38% and a 63%, respectively, by the treatment with the t-Res extract. Conclusions: A moderate consumption of t-Res from a dietary source resulted in a time-dose-dependent liver accumulation. It was able to counteract in vivo CCl(4)-induced liver lipid peroxidation thus demonstrating the hepatoprotective property of t-Res.
Studies show that the plant polyphenol resveratrol can extend the life span of yeast, worms, flies, and fish. It also mitigates the metabolic dysfunction of mice fed high-fat diets. Resveratrol appears to mediate these effects partly by activating SIRT1, a deacetylase enzyme that regulates the activity of several transcriptional factors and enzymes responsive to nutrient availability. However, few foods contain resveratrol and humans metabolize it extensively, resulting in very low systemic bioavailability. Substantial research effort now focuses on identifying and testing more bioavailable and potent activators of SIRT1 for use as pharmacologic interventions in aging and age-related disorders
Epidemiological studies show a link between the consumption of plant-derived foods and a range of health benefits. These benefits have been associated, at least partially, to some of the phytochemical constituents, and, in particular, to polyphenols. In the last few years, nutraceuticals have appeared in the market. These are pharmaceutical forms (pills, powders, capsules, vials, etc.) containing food bioactive compounds as active principles. The bioactive phytochemicals have become a very significant source for nutraceutical ingredients. Scientific research supports the biological activity of many of these food phytochemicals, but the health claims attributed to the final marketed nutraceutical products have often little or doubtful scientific foundation. This is due to the fact that a lot of the scientific evidence is derived from animal testing and in vitro assays, whereas human clinical trials are scarce and inconclusive. Some key issues such as bioavailability, metabolism, dose/response and toxicity of these food bioactive compounds or the nutraceuticals themselves have not been well established yet. Amongst the phytochemicals, several groups of polyphenols (anthocyanins, proanthocyanidins, flavanones, isoflavones, resveratrol and ellagic acid) are currently used in the nutraceutical industry. In this report, we have reviewed the most recent scientific knowledge on the bioavailability and biological activity of these polyphenols ('fact'), as well as the health claims (which are not always supported by scientific studies) ascribed to the polyphenols-containing nutraceuticals ('fiction'). The in vitro antioxidant capacity, often used as a claim, can be irrelevant in terms of in vivo antioxidant effects. Bioavailability, metabolism, and tissue distribution of these polyphenols in humans are key factors that need to be clearly established in association to the biological effects of these polyphenols-containing nutraceuticals. The future trends of phytochemistry research regarding nutraceuticals are discussed.
Resveratrol (3,4',5-trihydroxy-trans-stilbene) is a polyphenolic compound accounting to the stilbene class. Most stilbenes in plants act as antifungal phytoalexins, compounds that are usually synthesized only in response to infection or injury. Resveratrol has been detected in trees, in a few flowering plants, in peanuts, and in grapevines. The major dietary sources of resveratrol include grapes, wine, peanuts, and peanut products. Numerous in vitro studies describe different biological effects of resveratrol. The major impacts are the antioxidative, anti-inflammatory, and estrogenic effects as well as anticancer and chemopreventive activities. In order to reveal information on absorption, metabolism, and the consequent bioavailability of resveratrol, different research approaches were performed, including in vitro, ex vivo, and in vivo models, all of which are considered in this review. Summarizing the data, resveratrol is absorbed and metabolized. Around 75% of this polyphenol are excreted via feces and urine. The oral bioavailability of resveratrol is almost zero due to rapid and extensive metabolism and the consequent formation of various metabolites as resveratrol glucuronides and resveratrol sulfates. The potential biologic activity of resveratrol conjugates should be considered in future investigations.
Many in vitro studies demonstrated significant biological effects of trans-resveratrol. Thus, understanding the rate of intestinal absorption and metabolization in vivo of trans-resveratrol is the prerequisite to evaluate its potential health impact. Bioavailability studies mainly in animals or in humans using the pure compound at very high doses were performed. In this work, trans-resveratrol bioavailability from a moderate consumption of red wine in 25 healthy humans has been studied by three different experiments. The wine ingestion was associated to three different dietary approaches: fasting, a standard meal, a meal with high and low amount of lipids. Trans-resveratrol 3- and 4'-glucuronides were synthesized, purified, and characterized as pure standards. Bioavailability data were obtained by measuring the concentration of free, 3-glucuronide and 4'-glucuronide trans-resveratrol by high-performance liquid chromatography (HPLC), both with ultraviolet (UV) and mass spectrometry (MS) detection, in serum samples taken at different times after red wine administration. Free trans-resveratrol was found, in trace amounts, only in some serum samples collected 30 min after red wine ingestion while after longer times resveratrol glucuronides predominated. Trans-resveratrol bioavailability was shown to be independent from the meal or its lipid content. The finding in human serum of trans-resveratrol glucuronides, rather than the free form of the compound, with a high interindividual variability, raises some doubts about the health effects of dietary resveratrol consumption and suggests that the benefits associated to red wine consumption could be probably due to the whole antioxidant pool present in red wine.
