Polyphenols, such as resveratrol, anthocyanins, catechins and quercetin, are believed to help the body's cells resist damage by free radicals. Many have been found to have anti-cancer activity in the lab, and it is thought that they may be responsible for many of the benefits attributed to the Mediterranean diet, which is rich in foods with high polyphenol levels, like red wine, olive oil and other fruits and vegetables.
Yet studying polyphenols is complex as several different kinds can be found in one fruit alone and as yet, few researchers have tracked their individual consumption.
Stéphane Georgé and colleagues at the Avignon-based institute CTCPA (Centre Technique de la Conservation des Produits Agricoles) are among the first to look at the quantity of polyphenols being consumed by a European population.
After initially looking at consumption of total polyphenols from fresh fruit and vegetables, they will start next year to assess the amounts of specific polyphenols gained from a range of different foods, such as yoghurts, frozen foods, canned food and ready meals.
"This data will help epidemiologists studying the link between polyphenols and health benefits," Georgé told NutraIngredients.com.
With a more accurate picture of our intake, studies looking for associations with disease protection should also be more accurate.
"Lots of studies are looking at the health benefits of polyphenols. But now we can know how much of them we are really eating," Georgé added.
The Avignon team has already identified strawberries as the fruits with the highest total polyphenol count, followed by litchi, grapes, apricots and then apples. Among the vegetables, artichokes lead the way, with parsley, Brussels sprouts, shallots and broccoli all high in total polyphenols too.
But a further study, using data on food consumption gathered by the SUVIMAX trial, demonstrates that the potato is the richest source of polyphenols in a typical French diet, owing largely to its high consumption.
Presenting the results of this study last week at a conference on polyphenols organised by the Societe Francaise des Antioxydants, Georgé said : "The subjects had an average daily intake of 70mg polyphenols from vegetables and 200mg from fruits."
"In previous research it has been estimated that we consume about 1g of polyphenols per day. After the 270mg from fruit and vegetables, the rest probably comes from tea, wine and cereals."
The CTCPA has also been looking at how processing affects the polyphenol level in foods. Sterilisation, heat treatment and blanching vegetables all reduce their levels of polyphenols, and even though fresh fruit wrapped in plastic looks more appetizing to consumers than cans, it is equally damaging for polyphenols.
"We have developed a mathematical model that allows us to estimate the level of polyphenols in a food product based on the impact of each stage of processing it has been through," said Georgé.
Although there is still further work to be done on the bioavailability of polyphenols in the body, the French research is set to further our understanding of how we can improve our polyphenol uptake, with the potential to one day develop RDA's for these nutrients.