DNC News

DNC NEWS: Green tea protection against Dioxin

Subject:  Chemical constituents found in green tea offer protection against the toxin dioxin.

Dioxin is a cancer causing by-product of many combustion processes.  It is ubiquitous in our environment these days, including in the food we eat.  It is one nasty item.

One way to protect against this contaminant can be to rely on natural plant compounds that short circuit dioxin's toxicity.  A new study that came out last month suggests that green tea contains several natural chemicals and might provide dietary protection against dioxin.

Several different antioxidants found in green tea leaves have the potential to block dioxin's effect on its "docking point" within cells.  The most important of these chemical is epigallocatechin gallate (EGCG).  Remember this chemical because when I finally get around to finishing my article on chocolate you'll discover that a very similar chemical is in chocolate.  In this new green tea study Hitoshi Ashida of Kobe University and his buddies accessed the relative potency of 20 different compounds from green tea, including EGCG, in blocking the toxic action of dioxin.

Hitoshi found six compounds similar to EGCG in strength in defusing dioxin---three slightly more potent and the other slightly less potent.  None of these compounds has more than a miniscule concentration in tea; however several of them are abundant in other foods.

Among the stronger compounds, the antioxidant quercetin is plentiful in green apples, Kale and spinach are rich in the three slightly weaker alternatives to EGCG;;;chlorophyll-a, chlorophyll-b and lutein.  For people who aren't in to green leafy comestibles, the US Department of Agriculture is currently trying to figure out how to breed high - lutein carrots and potatoes. I'll reserve judgment until I taste them.

Here's the abstract of the green tea article:

J Agric Food Chem. 2004 May 5;52(9):2499-506 
Pigments in green tea leaves (Camellia sinensis) suppress transformation of the aryl hydrocarbon receptor induced by dioxin.

Fukuda I, Sakane I, Yabushita Y, Kodoi R, Nishiumi S, Kakuda T, Sawamura S, Kanazawa K, Ashida H.

Laboratory of Food and Nutritional Chemistry, Faculty of Agriculture, Kobe University, Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan.

Environmental contaminants such as dioxins enter the body mainly through diet and cause various toxicities through transformation of the aryl hydrocarbon receptor (AhR). We previously reported that certain natural flavonoids at the dietary level suppress the AhR transformation induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In this study, we identified lutein and chlorophyll a and b from green tea leaves as the novel antagonists for AhR. These active compounds suppressed AhR transformation dose-dependently with the 50% inhibitory concentration (IC(50)) values against 0.1 nM TCDD-induced AhR transformation at 3.2, 5.0, and 5.9 microM, respectively. (-)-Epigallocatechin gallate, which is the most abundant flavonoid in green tea leaves, also showed stronger suppressive effects than did other major tea components, with the IC(50) value of 1.7 microM. Thus, these pigments of green tea leaves have the potential to protect from dioxin toxicity through the suppression of AhR

PMID: 15113147 [PubMed - indexed for MEDLINE]

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