Tuesday, April 5, 2011

Green Tea Inhibits Fat Gain, But Will It Also Hinder Muscle Gain? Decreased Protein Absorption in Rats Supplemented With Green Tea Extract

It has gotten relatively quiet around green tea within the past weeks. Everybody knows about its anti-oxidant effects, its modest efficacy as a weight loss supplement and the relaxing effect of taking a time-out from the stressors of daily life with a good cup of freshly brewed tea. Now, scientists from Poland (Bajerska. 2011) found another interesting, yet not so beneficial property of green tea extract.

The scientists fed laboratory rats on a high fat diet chow with either 0%, 1.1% or 2.2% of green tea extract [GTAE] added and found that only the chow containing 2.0% GTAE had significant effects on body weight gain (5.6% less than control) and visceral fat accumulation (-17.8% vs. control). Yet, they observed a
[...] considerably (P < .05), reduction in the digestion of protein (but not fat) was observed in both GTAE groups (1.1% GTAE: 82.6% ± 1.8%; 2.0% GTAE: 84.3% ± 0.8%) when compared to the control (93.3% ± 1.5%).
This novel finding appears to stand in line with previous studies, in which green tea supplementation decreased fat absorption in the intestine. Interestingly, this effect was absent / non-significant in the current study (cf. figure 1).
Figure 1: Daily food intake, FER, apparent digestion of protein and fat, energy value of feces, and visceral fat content of treatment and control groups (Bajerska. 2011)
These findings have yet to be put into perspective, in order to assess how significant these results are for you, as a potential consumer of green tea supplements. Do you have to increase your protein intake if you consume one or two caps of green tea extract or the occasional cup of freshly brewed tea? Probably not. The rats in the study consumed 11g/kg, respectively, 20g/kg body weight of the extract. For a 80kg human being this would be a daily GTAE consumption of roughly 260g. Personally, even a teaspoon of GTAE makes me nauseous within minutes, so I guess none of you will even come close to this (over-)dose of supplemental green tea.

It is also noteworthy that, in view of the dose-response relationship between the amount of extract the rats consumed and its effect on their body weight, these results do also indicate that the amounts of GTAE you usually find in so-called "fat burners" will hardly have any direct effect on your body weight or fat, no matter what the respective supplement companies are telling you.