A new research finding, reported in the Journal of Nutritional Biochemistry is that green tea may strengthen gut health and protect against obesity.
The study was carried out at the Ohio State University and examined the impacts of green tea consumption on two groups of male mice. One was fed a high-fat diet over an 8-week period that intentionally led to obesity. The other group was given a regular diet. (Female mice were excluded because of their known resistance to diet-induced obesity.) Green tea extract was mixed into the food of half of each group. At the end of the two months, the research team examined (1) body and fat tissue, (2) evidence of leaky guts, inflammation in fat tissue and intestines and (3) the composition of gut microbes.
The results were striking. Mice given the high-fat diet supplemented by the green tea extract gained 20 percent less weight than those fed with just the obesity-inducing high-fat regimen. There was the same though less marked effect on the mice put on the regular diet supplemented with green tea. Other measures showed that the green tea supplement produced healthy bacteria for both diets: low resistance to insulin and less intestinal inflammation.
The obvious limitation on drawing conclusions from this study is that while mice are close to humans in their genetic, biological and behavioral characteristics, they are not identical and results from rodent studies – 95 percent of all subjects in medical testing – may not transfer to humans.
More consequentially, many reporters interpret the results as showing that green tea really does improve gut leakage. That is not scientifically grounded. Leakage is the postulated but unproven claim that the intestines’ protective wall can lose its impermeability and develop microholes. This gut leakage is seen as a generic illness by many nutritionists and a syndrome associated with bloating, gas, food sensitivities and cramps. Physicians are more likely to regard it as a hoax, euphemism for hypochondria, or a signal of some other illness needing diagnosis. More recently, there seems to be a shift towards consensus. Here’s the conclusion of the director of one of the leading nutrition clinics in the US: “We know that [leakage] exists… In the absence of evidence, we don’t know what it means or what therapies can directly address it.”
The human gut is extraordinarily complex and even the advanced technology of molecular biology has been unable to decipher its dynamics. Here are a few figures:
Small intestine, average length 23 feet. Large intestine: 5 feet
Bacteria: 40 trillion, mostly beneficial in stimulating vitamin formation, control of which nutrients and microorganisms get into the bloodstream, but also associated with many illnesses, including colon cancer, celiac and diabetes.
Estimates of bacterial species diversity: 1,000 to 40,000.
Gut bacteria reported as newly discovered in February 2019: 2,000.
Richard Bruno, the leader of the research team is cautious in his conclusion: “This study provides evidence that green tea encourages the growth of good gut bacteria, and that leads to a series of benefits that significantly lower the risk of obesity,” He stresses the need for human studies and evaluation of dosages and formulations of potential drug therapies. That’s a strong “may” assessment” but just that.
He is much more emphatic in his hopes and expectations: “Two-thirds of American adults are overweight or obese and we know that just telling people to eat less and exercise more isn’t working. It’s essential to develop complementary health-promoting approaches…” He informally estimates that drinking enough tea to provide the equivalent amount for humans of the tea extract would require cups a day.
The study is a first-rate design and it shows that green tea does affect obesity. It seems likely to have comparable impacts on humans.
Sources: Science Daily, WebMD, Harvard Health Publishing
CAPTION: Mice given green tea with high-fat diet gained 20 percent less weight than those fed with just the obesity-inducing high-fat regimen.