In a study published in the Journal of Nutritional Biochemistry, mice fed a diet of 2% green tea extract fared far better than those that ate a diet without it; the benefits stemmed from improved gut health, including more beneficial bacteria in the animals’ intestines and the reduced permeability of their intestinal wall.
Green tea polyphenols have the potential to improve skeletal muscle metabolism in obese mice by improving glucose homeostasis, reducing lipid peroxidation, and increasing rate limiting enzymes of oxidative phosphorylation. Image credit: Andi Ketaren.
Green tea has a rich history in Asian countries and has been increasingly embraced in the West, in part for its potential health benefits.
Catechins, anti-inflammatory polyphenols found in green tea, have been linked to anti-cancer activity and lower risk of heart and liver disease.
Ohio State University’s Professor Richard Bruno and colleagues suspected that green tea might prevent obesity and protect against inflammation in the gut based on previous studies, so they devised an experiment that examined green tea’s effects in male mice fed a normal diet and a high-fat diet designed to cause obesity. Female mice are resistant to diet-induced obesity and insulin resistance, a precursor to diabetes, so they weren’t included.
For eight weeks, half of the animals ate a high-fat diet designed to lead to obesity and half were fed a regular diet. In each of those groups, half ate green tea extract mixed in with their food.
The researchers then measured body and fat tissue weight, insulin resistance and other factors that included: (i) gut permeability, or how ‘leaky’ the gut was; (ii) endotoxin translocation, or the movement of a gut bacteria-derived component to the bloodstream, where it provokes inflammation and insulin resistance; (iii) inflammation in the fat tissue and intestines; (iv) the composition of the gut microbes, which are known to contribute to a variety of health factors.
The mice fed a high-fat diet supplemented with green tea gained about 20% less weight and had lower insulin resistance than mice fed an otherwise identical diet without tea.
Those mice also had less inflammation within fat tissue and the intestine. Furthermore, the green tea appeared to protect against the movement of endotoxin, the toxic bacterial component, out of their guts and into the bloodstream.
The scientists found evidence of stronger — less ‘leaky’ — guts in these mice. They also found that the green tea appeared to contribute to a healthier microbial community in the guts of the mice fed a high-fat diet.
Mice fed the normal, or low-fat, diet supplemented with green tea also had benefits including reduced weight gain and lower endotoxin levels and markers of leaky gut, but these were relatively modest compared with the effects seen in mice fed the high-fat diet.
“Green tea consumption in the experiment would be equivalent to about 10 cups of green tea throughout the day for a person,” Professor Bruno said.
“It might seem like a lot of tea, but it’s not highly unusual in certain parts of the world.”
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Eunhee Chung et al. 2019. Effect of annatto-extracted tocotrienols and green tea polyphenols on glucose homeostasis and skeletal muscle metabolism in obese male mice. Journal of Nutritional Biochemistry 67: 36-43; doi: 10.1016/j.jnutbio.2019.01.021
