Green tea extract improves gut health and glucose levels

A study published in June 2022 put forward the idea that green tea extract – which is rich in catechins – may reduce intestinal inflammation and lower fasting glucose levels in adults.

Written by Joanna Hodges, et al, the study – “Catechin-Rich Green Tea Extract Reduced Intestinal Inflammation and Fasting Glucose in Metabolic Syndrome and Healthy Adults: A Randomized, Controlled, Crossover Trial” – tested whether green tea extract (GTE) would help alleviate intestinal inflammation. They also noted a link with fasting glucose levels.

So – how does green tea improve gut health and glucose levels?

Catechins in green tea

Green tea consists of leaves from the Camellia sinensis plant, which proliferates mainly in Asia. It has several potential health benefits due to its high concentration of antioxidants and polyphenols. Recently, however, research has begun emerging about green tea’s antimicrobial properties – for which the important components are catechins.

Catechins are flavonoids and comprise 80–90% of flavonoids in green tea. This type of tea contains a higher concentration of catechins versus other forms of teas due to the way it is processed. Green tea is produced from mature tea leaves left unfermented – resulting in a potent amount of flavonoids and chlorophyll.

Green tea has four main types of catechins – EC, EGC, ECG and EGCG. Of the four, EGCG is the most abundant and has been the subject of much research.

The flavonoids – and therefore catechins – in green tea have many positive influences on our health. They have anticarcinogenic, anti-inflammatory, antioxidant and antimicrobial properties. This means they can help in the prevention and mitigation of conditions such as cardiovascular disease, diabetes, obesity and neurological disease.

In particular, green tea and catechins can help [1]:

  • Boost the creation of anti-inflammatory cytokines
  • Increase activity of antioxidant enzymes
  • Reduce bad cholesterol
  • Stimulate insulin secretion
  • Inhibit absorption of fat
  • Improve oral health

And now, new research has shown that green tea can improve a person’s gut health by reducing intestinal inflammation. It can also lead to a lower fasting glucose level.

Green tea consists of leaves from the Camellia sinensis plant, which proliferates mainly in Asia

The study by Joanna Hodges, et al, [2] determined that green tea extract (GTE) could reduce intestinal inflammation due to its high concentration of catechins. It noted that pre-clinical evidence showed GTE improved gut barrier function and reduced intestinal inflammation.

The methodology of the study involved having participants consume either placebo gummies or GTE gummies that contained the equivalent of 5 cups of green tea, for 28 days. Researchers then tested fecal and urine samples to measure inflammation and glucose levels.

Participants of the study followed a low-polyphenol diet to ensure no other polyphenol-rich food could interfere with results. Researchers also conducted the study in a randomised, double-blind and placebo-controlled manner. At day-0, day-14 and day 28 of the trial, they measured dietary polyphenols, fasting blood glucose and insulin levels.

Participants of the study followed a low-polyphenol diet to ensure no other polyphenol-rich food could interfere with results.

The study included both healthy persons and those who had metabolic syndrome (a group of conditions including high blood pressure, high blood sugar and abnormal cholesterol levels).

Fasting insulin remained unaffected by an intake of green tea extract, but fasting glucose decreased. Intestinal inflammation also saw a decrease in those with GTE-enriched diets. These results were consistent regardless of health status.

There are also related studies by Sergio Pérez-Burillo, et al [3] and Eun Sung Jung, et al [4] that study the effects of green tea supplementation on the human gut microbiome. These studies showed that green tea stimulated the growth of beneficial bacteria and hindered the growth of detrimental ones.

Other benefits of green tea

Besides improving gut health and blood glucose levels, green tea has plenty of other health benefits. It is rich in antioxidants, which combat oxidative stress in our bodies. Oxidative stress occurs due to an excess level of free radicals, which damage cells and play a key role in age-related degenerative conditions such as cancer.

Green tea also benefits our cardiovascular health – it can lower blood pressure and cholesterol levels, while reducing the risk of developing detrimental cardiovascular conditions. Some research has even shown that consuming 5 cups of green tea in a day lowers the mortality risk from a cardiovascular condition. [5]

Moreover, the caffeine in green tea stimulates the brain, allowing you to feel more alert and focused. The bioactive compounds in green tea might also enhance the performance of a person’s memory and thinking.

Should you drink more green tea for gut health and glucose control?

Green tea is an overall healthy drink and clearly has a beneficial place in our diets. But you should always consult a registered dietitian before consuming green tea extract as supplements or adding large quantities of green tea to your daily beverage intake. Still, there’s no harm in drinking a few cups of brewed green tea every day – not only is it good for you, but it’s tasty!

Drinking green tea for health

The catechins in green tea have several studied health benefits, including improving the conditions of our digestive systems and reducing glucose levels in the blood. They reduce inflammation in the gut, as well and potentially stimulate the growth of healthy bacteria in our stomachs.

While we shouldn’t be jumping to consuming 10 cups of green tea in a day, drinking a cup or 3 can help improve our overall health. You’ll boost your cognitive, cardiovascular and digestive function as well as potentially prevent skin cancer. Just remember to drink plain green tea or matcha – eating pastries or drinking bubble tea will have the opposite effect!

[1] https://www.sciencedirect.com/topics/neuroscience/catechin
[2] https://academic.oup.com/cdn/article/6/Supplement_1/981/6606956
[3] https://pubmed.ncbi.nlm.nih.gov/34206736/
[4] https://www.nature.com/articles/s41598-019-54808-5
[5] https://www.everydayhealth.com/diet-nutrition/diet/green-tea-nutrition-health-benefits-side-effects/

Photograph: Deenida/Shutterstock
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