Unexpected Side Effects of Flavonoid Supplementation: Do You have to Re-Evaluate the Use of EGCG, Grape Seed Extract & Co?

It is pretty exciting to see how scientists find new beneficial constituents in common foods on a daily basis. A group of these phytoprotectants is called "flavonoids". Respective extracts from grapes, green tea, etc. have been shown to exhibit various health benefits and supplement companies make a fortune selling them to health-conscious costumers. The question however remains: Did nature really intend us to consume these trace nutrients in such significant amounts?

Table 1: Potential beneficial and adverse effect of flavonoid supplements. (Egert. 2011)

Scientists from the Department of Nutrition and Food Science of the University in Bonn, Germany (Egert. 2011), have now taken a closer look at possible side-effects of a selection of these phytoprotectants. Among the possible interaction and health concerns the scientists have found were

• Flavonoid - trace element interactions - reduced the uptake of iron (and possible other trace elements)
• Flavonoid - vitamin interactions - folate, vitamin E and vitamin C absorption may be inhibited
• Flavonoid - thyroid interactions - increased risk of goiter and higher incidence of various forms of thyroid related illnesses

Last but not least, there are the effects on the cytochrome P450 pathway (hormonal interactions), possible interferences with specific medications and interactions with liver detoxification pathways (phase II enzymes in particular).

All this does not mean, that you should generally shy away from these nutrients. It shall only remind you of the fact that isolated in-vitro studies on certain beneficial effects of certain plant / fruit / legume extracts may not be enough to decide whether its worth risking unwanted side effects of inadequately researched "wonder supplements". Maybe, trying to get a diversified menu of flavonoids from a healthy and varied diet (yes, I am thinking of those of you who live on chicken breasts and broccoli), would be a viable alternative!?