Monday, July 18, 2011

Green Tea Dose-Dependently Sheds 7%-20% Body Weight in Mouse Model, But Higher Doses Turn Out to Be Pro- not Anti-Inflammatory In Recent Tufts Study

Image 1: A cup of freshly brewed
green tea (photo by Wikimol)
Green tea is healthy, it gets you going, will make you lose fat and calm down inflammation... wait! Is it possible that all that was just another marketing scam? Scientists from the Tufts University in Boston (Pae. 2011) have now found that at least in case of the capped green tea extracts, health (over-)conscious GNC-consumers are popping like candy, these days, the latter, i.e. the anti-inflammatory effect is absent.

And, it even gets worse, higher doses of a standardized EGCG extract (TEAVIGO; 95% EGCG content) even increased inflammation (measured via proinflammatory cytokines in the blood of the animals) in a group of 6-9 months old pathogen-free male mice who had been fed a diet enriched with 1% of the extract for 6 weeks:
Contrary to the assumption that EGCG would reduce inflammatory response, mice fed 0.15% and 0.3% EGCG diet exhibited no change while those fed 1% EGCG diet produced more proinflammatory cytokines tumor necrosis factor-α, interleukin (IL)-6, and IL-1β and lipid inflammatory mediator prostaglandin E2 in their splenocytes and macrophages (MΦ) and less IL-4 in splenocytes.
In that, it is quite interesting that the cytotoxicity of the green tea extract didn't hinder it from unfolding its unquestionably more marketable potential to reduce body weight.
Figure 1: Body weight of ECGC treated in the course of the 6 week treatment period; expressed relative to the weight of the unsupplemented control group (data calculated based on Pae. 2011)
As the data in figure 1 indicates, all three levels of EGCG enrichment produced statistically significant and surprisingly instantaneous reductions in body weight. The mean weight difference to the control group were -7%, -12%, -20% for the 0.15%, 0.3% and 1% EGCG groups, respectively. Based on previous research on the weight loss effects of EGCG extracts, Pea et al. hypothesize that the underlying mechanisms "involve decreased energy/lipid absorption and lipogenesis",  "increased fat oxidation" and improved glucose tolerance. Since the authors of respective studies were interested mainly in the weight loss effect, they failed to measure inflammatory status, as well, which is why Peat et al. are unable to tell, whether these beneficial metabolic effects are associated or even stem from EGCG's effect on inflammation status.

To evaluate the potentially detrimental effects of the wide-spread use of commercially available green tea extracts, the authors conduct the following dose-equivalent calculation:
Based on the average mice's consumption of 3 g/days, diets containing the medium dose (0.3%), or 3 g EGCG /kg diet, provided mice with a daily intake of 9 mg EGCG, or 300 mg/(kg BW/d) for a mouse of 30 g (average BW in the current study). When this dose is converted from mice consuming 12 kJ/day to humans consuming 2000 kJ/day by using isocaloric calculation, it is roughly equivalent to 22 mg/(kg BW/day) in humans, or 1540 mg EGCG per day consumed by a 70-kg person. Likewise, the low dose (0.15%) and high dose (1%) of EGCG for mice in this study are equivalent to human daily consumption of 770 and 5040 mg, respectively.
In view of the fact, a cup of tea contains only 150−180 mg EGCG, it is unlikely that habitual green tea (~3-5 cup = 450-900mg EGCG) consumption will increase daily intake to the "critical" level of  commercially available EGCG - it could, on the other hand, suffice to induce beneficial effects on body weight, glucose management and fatty acid metabolism.
Did you know that in many studies concentrations of 50µmol/L, i.e. roughly 230,000mg of epigallocatechin-3-gallate per liter, were used to elicit the often cited health benefits of the green tea phytochemical? In animal models, however, even a dose of 2,000mg/kg body weight incresed plasma concentrations to levels slightly below 1/5th (9µmol/L) of what has been studied in the petri dish.
In case of the consumption of commercially available EGCG caps, which contain anywhere from 150-900 mg EGCG/tablet (depending on capsule size and purity of the extract), the more-is-more mentality of our society along with the desire to lose weight as quickly as possible could however lead to epigallocatechin-3-gallate intakes at levels equivalent to those that were achieved in the study and would thus leave consumers slim, but heavily inflamed. So, if you want to avoid that, you better stick to the suggested serving size (in case of the NOW Foods EGCG product, for example, this practice would deliver ~600mg in three divided doses per 24h), instead of going through your cost-effective 250g bottle of bulk 90% EGCG extract within a single month :-)