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!?

Ginkgo, Ginseng, Green Tea: Only one of the G's may be worth Supplementing

In the most recent episode of their supplement review (which is usually very critical) the British Journal of Sports Medicine (BJSM Review. Part 17) has a look at studies on the ergogenic potential of ginkgo, ginseng and green tea, all of which are heavily advertised for their beneficial effects on health, long jeopardy and mental, as well as physical performance.

In the case of Ginkgo an Ginseng, the studies that have been considered in this review provide very inconclusive evidence for and against their use as ergogenics or medical plants. With regards to the underlying reasons for the discrepancies which have been reported, the reviewers argument that both, the origin, as well as the processing techniques may have influenced the efficiency of ginkgo and ginseng products. green tea, on the other hand, "shows some promise" - regular readers of this review series will know that this is already a great praise!

Although evidence is limited, green tea extract, and particularly the active component EGCG, has shown some consistency from animal to human models regarding a delay in fatigue during prolonged exercise. In humans this appears to be due to the effect of an increase in fat oxidation.

Against this background and in view of the declining prices of quality green tea products (especially if bought in bulk) green tea should obviously be the "G" of choice in your supplement regimen. Ah, and before I forget: green tea is actually something you drink, basically the counterpart to real food, which is what you probably have forgotten to eat facing the stash of capsuled supplements you're popping everyday ;-)

Brewing the Perfect Green Tea: Best Brewing Time and Temperature for Optimal Potency

Here is something for all of you who have always asked themselves how to prepare their tea to "get the most out of it". Well, I know normal people would go by taste, but are we normal? No! We want maximal antioxidant-content and a decent amount of caffeine to jack us up and this is where the results from a recent study (Ziaedini. 2010) come into play.

The scientists from the Iranian Institute of Research and Development in Chemical Industries investigated the effect of different brewing times and temperatures on the amount of antioxidants and caffeine you'll get in your tea. Here are the results (cf. table 1):

Table 1: Diffusion coefficients of catechins and caffeine obtained for conventional extraction of green tea leaves.

Obviously it takes a decent temperature of ~70°C to achieve maximal diffusion of the constituents in the short and in the long term. In spite of that, a close look at one of the graphs (cf. figure 1)

Figure 1: EGCG content as a function of time for different water temperatures in °C

shows that even with decent temperatures (>70°C) it takes some time for the antioxidant content (in this case the infamous ECGC content) to achieve significant levels - and lets be honest, do you like, or even, can you really drink a tea that has been brewed for 10 or even 20 minutes? If you can, you're the man (or woman) - if not you probably better buy some capped extract ;-)