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New research demonstrates green tea’s effects on gut health. Sunphol Sorakul/Getty Images
  • A new study became the first to assess whether green tea’s anti-inflammatory benefits in the gut could impact health risks linked to metabolic syndrome.
  • The study shows consuming green tea extract may reduce blood sugar levels and decrease gut inflammation and permeability.
  • Researchers reported that both participants with metabolic syndrome and healthy participants saw health benefits from consuming extract.

An abstract of a study published in Current Developments in Nutrition looks at whether health risks associated with a set of risk factors known as metabolic syndrome may be diminished by consuming green tea extract.

The researchers from Pennsylvania State University and Ohio State University say they’re the first to study whether green tea’s anti-inflammatory benefits in the gut could reduce health risks associated with metabolic syndrome, a name referring to a cluster of factors that raise an individual’s risk of experiencing coronary hearth disease, diabetes, and other health problems.

The American Heart Association (AHA) lists those risk factors as: high blood glucose, low HDL (“good” cholesterol), high triglycerides, large waist circumference, and high blood pressure.

A 2015 study found nearly 35% of adult Americans and 50% of Americans age 60 and older were estimated to have metabolic syndrome.

Dr. Richard Bruno, senior study author and professor of human nutrition at Ohio State, has studied whether the properties of green tea can help to alleviate the risk of cardiometabolic disease for more than 15 years.

Dr. Bruno explained in a statement to Medical News Today that his research team’s earlier research on rodents found green tea supplements decrease cardiometabolic complications “in association with” improved gut health, including an increase in beneficial microbes in the intestines and less permeability in the intestinal wall.

That research, as well as a drive to give people a “food-based tool” to improve their health, inspired the current study.

Dr. Bruno and his team conducted a clinical trial with 40 participants. Of these, 21 had metabolic syndrome and 19 were healthy adults. The participants were primarily white, with other racial/ethnic groups “represented but to a limited extent.”

The participants were given gummies containing catechins, which equaled five cups of green tea, for 28 days. All participants spent another 28 days taking a placebo, with a month in between where they took no supplements.

Since green tea is rich in polyphenols, a compound also found in foods like berries and apples, participants ate a diet low in polyphenols over the course of the study.

Researchers conducted tests monitoring the participants’ fasting blood glucose, insulin, lipids, and dietary polyphenols before the study began and on days 14 and 28 of each intervention. They used pooled stool samples to assess intestinal inflammation.

Participants completed the study with high compliance and reported no adverse effects or changes in body mass.

The researchers found green tea extract lowered blood sugar and decreased gut inflammation and permeability in both healthy people and people with metabolic syndrome.

“The findings in humans are quite exciting because they confirm some of the findings that were previously observed in rodents that were supplemented with green tea,” Dr. Bruno explained.

“The importance of gut health for humans is exemplified by our research and suggests that dietary factors such as green tea that are rich in catechins can help to reduce the risk of glucose intolerance by limiting gut inflammation and improving gut integrity.”
— Dr. Richard Bruno

Individuals with metabolic syndrome often aren’t given medical treatment beyond being told to diet and exercise. “Our work shows that regular green tea consumption has the potential to be part of the solution to manage the risk of metabolic syndrome,” Dr. Bruno said.

Roxana Ehsani, a registered dietitian, nutritionist, and national media spokesperson for the Academy of Nutrition and Dietetics, noted that the amount of green tea extract consumed by the study’s participants could be problematic for some people.

Consuming green tea extract in high doses, she pointed out, can be toxic and lead to organ damage.

Ehsani also said it would have been helpful if the study had noted whether the participants were given decaf or caffeinated green tea extract.

This study is in line with others that show the health benefits of green tea, Kristin Kirkpatrick, a registered dietitian nutritionist and author, told MNT in an email.

“Inflammation is the base of any disease and can impact chronic disease risk, gut health, and mental health,” she wrote. “Therefore, regular consumption of green tea may help to benefit health beyond what was seen in this study.”

However, Kirkpatrick said she wouldn’t be quick to recommend consuming green tea extract to a client.

“Since the supplement industry is not regulated, I would most likely focus on [drinking green tea] over a supplement form,” she said.

The key when drinking green tea, according to Kirkpatrick, “is to be a purist and drink green tea or matcha without any additives or added sugars.”

Too much to tolerate

Since participants in the study consumed extract equal to five cups of green tea, most folks may find it difficult to drink the equivalent of tea in a single day, Ehsani told MNT.

“For most people, this may be too much caffeine to tolerate,” she said, adding that drinking a single daily cup of green tea as a habit may also render health benefits.

“Drinking [a single cup of] green tea every day and consuming a diet rich in fruits and veggies can and will also benefit a person’s fasting blood sugar.”
— Roxana Ehsani, nutrionist

Individuals who want to consume green tea supplements should speak with their doctors first, Ehsani stressed, cautioning:

“[H]igh doses of green tea extract may be toxic and may interfere with any other supplements or medications you are also taking,” she wrote.

Currently, Dr. Bruno and other researchers are looking at green tea and microbiota, a community of micro-organisms in the gut, to better understand whether green tea increases the levels of healthy bacteria while decreasing pathogenic populations of bacteria.

“This will help in our understanding,” Dr. Bruno told MNT, “how green tea improves gut health and whether shifts in bacteria population predict effective responses to green tea consumption.”