Flavonoids are water soluble plant pigments that plants produce to assist in photosynthesis and are believed to function as antioxidants. Major dietary sources of flavonoids include fruits, vegetables, cereals, tea, wine and fruit juices.

The main groups of flavonoids and their food sources are:

• flavonols – found in onions, leeks and broccoli;
• flavones – found in parsley and celery;
• isoflavones – found in soyabeans;
• flavanones – found in citrus fruit and tomatoes;
• flavanols – abundant in green tea, red wine and cocoa; anthocyanidins’ sources include red wine and red berries.

A recent study has provided strong evidence that dietary flavonoid intake preserved cognitive abilities with aging. Isoflavones from soy had positive effects on cognitive function, because they were able to mimic the actions of estrogens in the brain. Isoflavone supplementation had a favourable effect on verbal memory in post-menopausal women.

Brain-imaging studies in humans have demonstrated that the consumption of flavanol-rich cocoa may enhance blood flow to the brain cortex. Berries, in particular blueberries, are effective at reversing age-related deficits in movements and memory.

Animal studies with tea, grape juice or flavonols such as quercetin have shown that they all are beneficial in reversing the course of neuronal and behavioural ageing. Such beneficial effects have been attributed to antioxidant activities, however, there are growing body of evidence that their mechanisms involve a modulation of neurotransmitter release, a stimulation of neurogenesis and changes in neuronal signaling.

Source: Proceedings of the Nutrition Society (2008), 67: 238-252