'So far the biological and protective activities of various flavonoids have been extensively studied in vitro, on cell-based assays,' explains researcher and leading author of the study, Dr Marie-Claire Toufektsian of Joseph Fourier University in Grenoble, France. 'Nevertheless, this kind of approach has a major limitation: it is extremely difficult to assess precisely the nature of all flavonoids absorbed following consumption of plants present in a given meal.'
In other words, 'laboratory cultured cells alone are not sufficient to study a complex mechanism such as that of absorption of food flavonoids,' she says. For this reason, the researchers decided to study the effects on animals of ingesting plants that are rich in polyphenols. Two kinds of corn were chosen for the study; one containing anthocyanin, a type of flavonoids, and another anthocyanin-free variety.
The corn seeds were given to rats as part of their diet over a couple of months. The researchers measured the anthocyanin levels in the urine and plasma from the rats in the two groups, and then looked out for changes to the myocardial (heart) and signs of myocardial infarction or heart attack.
'We found that chronic consumption and effective absorption of anthocyanins rendered the rats more resistant to myocardial infarction,' says Dr Toufektsian. 'In other words, the size of the infarct was significantly reduced in rats fed the anthocyanin-rich diet.'
Dr Toufektsian goes on to say that while the results are promising, care must be taken because the cellular mechanisms of the protection are not clearly determined yet. 'There may be differences between humans and rats, for example, in terms of flavonoid absorption and metabolism,' she adds.
It is also important to take into account the quantity of anthocyanin eaten by the rats. 'The rats fed the anthocyanin-rich diet received about 13-fold more anthocyanins than most people following a standard Western-type diet, where the daily consumption of flavonoids is relatively low and the average intake of anthocyanins is estimated to be only 12 mg per day,’ explains FLORA’s scientific coordinator, Maria Benedetta Donati of the Catholic University in Campobasso, Italy.
The Mediterranean diet was also examined by the researchers, because of its flavonoid-rich content. 'The anthocyanins content of the traditional Mediterranean diet is much higher than that of the Western diet, which might explain why the Mediterranean diet is cardioprotective,' notes Dr Michel de Lorgeril, also of Joseph Fourier University.
The FLORA project now hopes to follow up the study with research with human volunteers on the beneficial effects of anthocyanins from blood orange juice, one of the most generous sources of flavonoids.