According to recent research conducted on individuals with a cluster of heart disease risk factors, ingesting green tea extract for four weeks can decrease blood sugar levels and enhance gut health by reducing inflammation and “leaky gut.”
This study, according to researchers, is the first to examine whether the anti-inflammatory properties of green tea may have a protective effect against the health risks associated with metabolic syndrome, a disease that affects more than three million Americans each year.
“There is much evidence that greater consumption of green tea is associated with good levels of cholesterol, glucose, and triglycerides, but no studies have linked its benefits in the gut to those health factors,” said Richard Bruno, senior study author and professor of human nutrition at The Ohio State University.
The clinical trial, which included 40 people, was a follow-up to a 2019 study that revealed improved gut health was connected with reduced obesity and fewer health risks in mice that received green tea supplements.
Unexpectedly, the new study found that green tea extract also reduced gut inflammation and permeability in healthy individuals, as well as blood sugar, or glucose.
“What this tells us is that within one month we’re able to lower blood glucose in both people with metabolic syndrome and healthy people, and the lowering of blood glucose appears to be related to decreasing leaky gut and decreasing gut inflammation – regardless of health status,” Bruno said.
Articles on the glucose results and lowered gut permeability and inflammation were published recently in the journal Current Developments in Nutrition.
At least three of the five risk factors for heart disease, diabetes, and other health issues—excess belly fat, high blood pressure, low HDL (good) cholesterol, high levels of fasting blood glucose, and triglycerides, a form of blood fat—are present in people with metabolic syndrome.
The tricky thing about these risk factors that constitute metabolic syndrome is that they are often only slightly altered and do not yet require drug management, but still impose great risk to health, Bruno said.
“Most physicians will initially recommend weight loss and exercise. Unfortunately, we know most persons can’t comply with lifestyle modifications for various reasons,” he said. “Our work is aiming to give people a new food-based tool to help manage their risk for metabolic syndrome or to reverse metabolic syndrome.”
Forty participants – 21 with metabolic syndrome and 19 healthy adults – consumed gummy confections containing green tea extract rich in anti-inflammatory compounds called catechins for 28 days. The daily dose equaled five cups of green tea. In the randomized double-blind crossover trial, all participants spent another 28 days taking a placebo, with a month off of any supplement between the treatments.
Researchers confirmed that participants, as advised, followed a diet low in polyphenols – naturally occurring antioxidants in fruits, vegetables, teas, and spices – during the placebo and green tea extract confection phases of the study so any results could be attributed to the effects of green tea alone.
Results showed that fasting blood glucose levels for all participants were significantly lower after taking green tea extract compared to levels after taking the placebo. Decreased gut inflammation due to the green tea treatment in all participants was established through an analysis that showed a reduction in pro-inflammatory proteins in fecal samples. Using a technique to assess sugar ratios in urine samples, researchers also found that with green tea, participants’ small intestine permeability favorably decreased.
Gut permeability, or leaky gut, enables intestinal bacteria and related toxic compounds to enter the bloodstream, stimulating low-grade chronic inflammation.
“That absorption of gut-derived products is thought to be an initiating factor for obesity and insulin resistance, which are central to all cardiometabolic disorders,” Bruno said. “If we can improve gut integrity and reduce leaky gut, the thought is we’ll be able to not only alleviate low-grade inflammation that initiates cardiometabolic disorders but potentially reverse them.
“We did not attempt to cure metabolic syndrome with a one-month study,” he said. “But based on what we know about the causal factors behind metabolic syndrome, there is potential for green tea to be acting at least in part at the gut level to alleviate the risk for either developing it or reversing it if you already have metabolic syndrome.”
Bruno’s lab is completing further analyses of microbial communities in the guts of study participants and levels of bacteria-related toxins in their blood.
“Catechin-Rich Green Tea Extract Reduced Intestinal Inflammation and Fasting Glucose in Metabolic Syndrome and Healthy Adults: A Randomized, Controlled, Crossover Trial” by Joanna Hodges, Min Zeng, Sisi Cao, Avinash Pokala, Shahabbedin Rezaei, Geoffrey Sasaki, Yael Vodovotz and Richard Bruno, 14 June 2022, Current Developments in Nutrition.
“A Green Tea Extract-Rich Confection in Healthy and Metabolic Syndrome Adults Decreases Small Intestinal Permeability in Association With Lower Gut Inflammation” by Min Zeng, Joanna Hodges, Geoffrey Sasaki, Sisi Cao, Yael Vodovotz and Richard Bruno, 14 June 2022, Current Developments in Nutrition.
This work was supported by the U.S. Department of Agriculture and the Ohio Agricultural Research and Development Center at Ohio State.
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