Sense and Nonsense of Dietary Supplements

Scientific evaluation of Cardiovascular health benefits of dietary supplements

Grapes, glass and bottle

Resveratrol

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Resveratrol belongs to the class of flavonoids . Resveratrol has experienced a tremendous boost in popularity over the past decade. Resveratrol is marketed as the active component that is responsible for the demonstrated health benefits of red wine. However convincing scientific evidence is lacking.

There is no published evidence anywhere in the scientific literature of clinical trials that substantially demonstrate efficacy of Resveratrol in humans. There are limited human safety data. Long-term safety has not been evaluated in humans. Small trials investigated safety and dosage and efficacy but found negative results ( 1, 2 ). 


Longevity

The groups of Howitz and Sinclair reported in 2003 in Nature, that resveratrol significantly extends the lifespan of the yeast Saccharomyces cerevisiae. Later studies showed that resveratrol also prolongs the lifespan of the worm, Caenorhabditis elegans, and the fruit fly, Drosophila melanogaster. In 2007, a different group of researchers were able to reproduce Sinclair's results with C. elegans, but a third group could not achieve consistent increases in lifespan of either D. melanogaster or C. elegans.

In 2006, Italian scientists obtained the first positive result of resveratrol supplementation in a vertebrate. Using a short-lived fish, Nothobranchius furzeri, with a median life span of nine weeks. They found a maximal dose of resveratrol increased the median lifespan by 56%. Compared with the control fish at nine weeks, the fish supplemented with resveratrol showed significantly higher swimming activity and better learning to avoid an unpleasant stimulus. The authors noted a slight increase of mortality in young fish caused by resveratrol.

A further study by a group of scientists, which included Sinclair, indicated resveratrol treatment had a range of beneficial effects in elderly mice, but did not increase the longevity of ad libitum–fed mice when started midlife. Later, the National Institute on Aging's Interventions Testing Program (ITP) also tested three different doses of resveratrol in mice on a normal diet beginning in young adulthood, and again found no effect on lifespan, even at doses roughly eight times higher than those that had normalized the lifespan of the high-fat-fed, obese mice in the earlier study.


Cardiovascular disease risk

Sinclair also reported resveratrol counteracted the detrimental effects of a high-fat diet in mice. Mice on the high-fat diet became obese, diabetic and exhibited a high mortality rate compared to mice fed the standard diet. Mice fed the high-fat diet plus resveratrol had a 30% lower risk of death than the mice on the high-fat diet alone, making their death rates similar to those on the standard diet. Resveratrol supplements did not change the levels of free fatty acids and cholesterol, however, which were much higher than in the mice on standard diet. However, these results have not been evaluated in human trials. A recent trial did show that a supplement containing grape extract with 8 mg resveratrol caused a decrease in hs-CRP levels of 26% after 1 year. Whereas placebo and grape extract without resveratrol did not show a reduction in hs-CRP. 

Conclusion

Traffic light Red There are indications of health benefits of Resveratrol in animal studies, but most are derived from one single research group led by Prof. Sinclair. Therefore there is a high chance of bias and thus Resveratrol supplements cannot be recommended based on currently available scientific evidence. Larger trials performed by independedn scientist should performed to provide the rerquired scientific evidence to support daily Resveratrol supplementation.

Reference List

  1. Boocock DJ et al. , Phase I dose escalation pharmacokinetic study in healthy volunteers of resveratrol, a potential cancer chemopreventive agent. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology 16 , 1246-52 (Jun, 2007).
  2. Poulsen MM et al. , High-Dose Resveratrol Supplementation in Obese Men: An Investigator-Initiated, Randomized, Placebo-Controlled Clinical Trial of Substrate Metabolism, Insulin Sensitivity, and Body Composition. Diabetes ,  (Nov 28, 2012).

 

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