Flavonoids are a group of substances found in plants which prevents the cancer forming. There are three important groups and they are flavonoids, isoflavonoids and neoflavonoids. These are known for their strong anti-oxidant activity.

The flavonoids have less toxicity and this is the reason for cancer prevention. The body sees flavonoids as foreign substances and with the help of the detoxification system these are excreted. In the same process cancer producing substances are also eliminated. Small amount is necessary for this purpose in our body and high dose supplements are not recommended.

More than 5,000 flavonoids from various plants are isolated and characterized in different groups. This number can go up in future. Few rich sources of flavonoids include:

• Grapefruit - There are six flavonoids found in this citrus fruit including quercetin and they increase the intracellular levels of vitamin C, has positive effects on capillary permeability and blood flow.

• Ginkgo – The active ingredient of ginkgo is flavoglycosides and is extracted from the ginkgo leaves. It is also sold as herbal supplement.

• Green Tea – Catechins and epigallocatechins are potent antioxidants and these may help to prevent cancer. But black tea does not have catechin because it is lost by oxidation during the processing.

• Bitter Chocolate – bitter chocolate from cacao contains also flavonoids.

• Wine - Flavonoids as well as polyphenols are found on grape skins and both red and white wine contain the flavonoids. Red wine contains more flavonaids and other polyphenols such as resveratrol.

Most of the flavonoids are important but quercetin and epicatechin are in the upper part of the list. Quercetin is anti-cancer agent and is also a strong antioxidant.

Bitter chocolate has epicatechin which supports heart by improving the blood flow.