In the third part of a special series on resveratrol, NutraIngredients looks at the science behind the ingredient. Is the French Paradox exclusively due to resveratrol?
Resveratrol, a powerful polyphenol and anti-fungal chemical, is often touted as the bioactive compound in grapes and red wine, and has particularly been associated with the so-called 'French Paradox'. The phrase, coined in 1992 by Dr Serge Renaud from Bordeaux University, describes the low incidence of heart disease and obesity among the French, despite their relatively high-fat diet and levels of wine consumption.
“Beginning in the early 1990s the word resveratrol started beeping on people’s radar screens,” said Bert Scwhitters, President of INC, a supplier of oligomeric proanthocyanidins (OPCs).
Live longer, live healthier
In 2003, David Sinclair and his team from Harvard added life extension to the list of possible benefits with the publication in Nature that resveratrol increased the survival of yeast cells.
Since then studies in nematode worms, fruit flies, fish, and mice have linked resveratrol to longer lives. Further studies with only resveratrol have reported anti-cancer and anti-inflammatory effects. The molecule appears to offer considerable health benefits, and was described by Bill Sardi, co-founder and president of Resveratrol Partners as “one of the most promising molecules on the planet”.
However, attributing the French Paradox solely to resveratrol is a separate issue, and questions over the dosages used to achieve the benefits appear to put this link in doubt.
Some suppliers of resveratrol admit that the link between resveratrol and the French Paradox is not clear cut. “The jury is still out debating on that one,” said Sami Sassi, product manager for Danish company Fluxome. “Red wine and resveratrol may be one of the reasons for the paradox,” he added.
“Resveratrol is still a superlative molecule, but we know the French Paradox occurs in a milieu of molecules that includes resveratrol,” said Sardi, whose company offers the Longevinex product.
Dipak Das, PhD, from the University of Connecticut disagrees. “We are sure that resveratrol is behind the French Paradox,” he said. On the dose question he says “this is very controversial. You have some folks at Harvard saying you need lots, something like 30 bottles per day. We believe we need only very little.”
Considering that one glass of wine contains between one and two micrograms of resveratrol, daily intakes from all sources will give you between 5 and 10 mg, “if you’re lucky”, said Schwitters, then we are still far away from the doses used in many of the animal studies.
“Even if you take supplements with doses of 30 to 150 mg this is still not enough to achieve the quantities that produced the wonderful effects in test animals,” said Schwitters.
“Resveratrol is often presented as the healthy ingredient in red wine, but the moment you start recommending 20, 30, or 100 times the average daily intake, you can no longer make the comparison to red wine,” he added.
The sum greater than the parts?
Studies continue to muddy the waters, however. For example, Italian scientists reported in the Journal of Nutrition last year that found that resveratrol “at concentrations attainable after moderate wine intake” could stimulate the production of nitric oxide, a compound known as a vasodilator, which can lead to blood vessel relaxation, reductions in blood pressure, and improvements in heart health.
A review of the evidence is provided by Linus Pauling Institute at Oregon State University, which states that convincing evidence is currently lacking to support resveratrol’s cardioprotective effects in humans, “particularly in the amounts present in 1 to 2 glasses of red wine”.
Studies are now looking at the synergies with other compounds in wine, including OPCs, catechins, and other polyphenols.
Prof Roger Corder from Barts and the London School of Medicine and Dentistry in London, and author of The Wine Diet, asserts that it is the total polyphenols that are responsible for the French Paradox.
Bill Sardi is surer: “We can achieve an anti-ageing pill,” he said. “It’s liquid and it’s corked!”
In an upcoming article NutraIngredients will look at the science behind pure resveratrol.