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Can a cup of green tea boost your gut health?

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Analysis: if you’re looking for a New Year’s resolution, here’s why you need to start drinking green tea

By Joanna Michalina Jurek, UCC and Nicola Stanislawska

Looking for a New Year health resolution? Start drinking green tea – not only for weight loss or increasing your energy level, but for your gut. Researchers have found drinking about 4 cups of green tea over minimum 10 days can significantly improve your gut microbiome and increase levels of beneficial microbes, like Bifidobacteria.

Most teas we know — no matter if it’s black, green or white — are made of the same plant, known as Camellia Sinensis; nevertheless the way they are harvested, stored and finally processed significantly impacts on their health promoting effects, attributed to the content of various bioactive molecules, known as polyphenols.

Polyphenols are a group of over 8000 bioactive molecules found in various plants, predominantly fruits and vegetables, that can be further divided into flavonoids, phenolic acid, stilbene and lignans etc., which protect the plants against harmful microbes, board damage, and damage caused by free radicals. Polyphenols can be beneficial for us as well, as including them as a part of our diets may protect us against cancer, cardiovascular diseases, diabetes, osteoporosis and aging.

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From RTÉ Radio 1’s Drivetime, are tea bags biodegradable?

Although some of us still struggle to get their polyphenols through the “five (recommended) fruit and vegetable portions a day”, we can still get it through other sources, such as a nice morning or afternoon cupán tae, which, let’s be honest , is a must have of each day.

However, the amount of polyphenols may be different depending on the tea itself as well as the way it is drunk. For example, white or green tea being made from young tea leaves, subjected to mild processing, is rich in bioactive molecules, in particular natural antioxidants. On the other hand, black tea prepared from older leaves that are dried, crushed, and then intensively processed, known as oxidation, have less polyphenols but more caffeine and tannins.

Level of oxidation is not the only determinant of the tea flavor and amount of natural antioxidants, this also depends on the way you drink it. This is why you should definitely keep an eye on the brewing time and water temperature you use, as long and boiling water can destroy healthy biomolecules. Also, adding sugar to your tea, as well as milk, honey, and even a slice of lemon, can influence the health effects.

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From RTÉ Radio 1’s Marian Finucane, author Fiann O’Nuallain talks about herbal teas and their health benefits

Do not feel discouraged from drinking a traditional black tea, as research has shown that (any) tea consumption, being equal to or more than three cups a day, was linked with a lower risk for developing type II diabetes, compared with lower intakes, or not drinking tea at all. Interestingly, for each cup consumed within the day, even accounting for the fact that black tea has less antioxidants than green tea, you can still get serious benefits for your health: an additional 4% lower risk of dying from cardiovascular disease and a 2% lower risk of cardiovascular events, including a 4% lower risk of stroke.

Although both black and green teas if drunk regularly for at least 3 months efficiently reduced both systolic and diastolic blood pressure (by about -3.53 and -0.99 mmHg), green tea was more powerful than the black one; and most importantly, consumption of green tea, but not black tea, may reduce fasting glucose levels in the blood, when compared to drinking water.

The super-powers of the green tea are attributed to high polyphenol content, being dominated by catechins, which not only supercharge antioxidant levels of your body, but may boost beneficial microbes in your gut as well. Interestingly, the main catechins found in green tea, epigallocatechin-3-gallate (EGCG) can significantly increase the abundance of probiotic bacteriasuch as Bifidobacterium and Lactobacillus, exactly in the same way as eating fermented foods (kefir, yogurt, sauerkraut etc.) or high in dietary fiber products (oat bran, whole grains, porridge etc.) do.

These bacteria are extremely important for us, they support our digestion and immune function; whereas their metabolites, known as short chain fatty acids, acetate and butyrate, can help in maintaining a healthy gut and prevent inflammation.

Furthermore, catechins from green tea can also limit growth of potential pathogenic bacteriasuch as Bacillus cereus, Campylobacterjejuni, Clostridium perfringens, Escherichia coli, Helicobacter pylori, Legionella pneumophila, and Mycobacterium spp., previously being linked to higher risk of developing colorectal cancer, inflammatory bowel disease or obesity.

Boost your gut health in less than 2 weeks by drinking green tea

Even if you haven’t been a “green tea-drinker”, if you start now and gradually scale up your tea consumption to roughly 4 cups a day (1000 ml of green tea a day), after 10 days, you may significantly increase the proportion of Bifidobacteria in your gut. Just one word of warning – if you stop it, after 7 days, your Bifs can go downso you will be better off forming a habit out of that.

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From RTÉ Archives, tea expert and professional tea taster Owen Dawson on how to identify different teas (first broadcast 13 April 1988)

As not everyone must enjoy a plain green tea, don’t be afraid to get creative:

Add cinnamon, ginger powder, a slice of lemon and cardamon to your cup of green tea for a spicy, warming-up version.

Boost your immunity with turmeric, black pepper and lemon added to your green tea.

Some ideas how to make your green cuppa more ininteresting:

Make a Green Tea Chicken soup – use brewed green tea to make unusual chicken soup with garlic and baby spinach. For the full recipe go here.

Try out Ochazuke – a Japanese-inspired nutritious dish made with green tea broth, noodles, Asian greens and salmon. Find instructions here.

Use green tea as marinade – combine brewed cup of green tea with Dijon mustard, oregano, marjoram and olive oil for unique marinade for steak. Find full recipe here. Alternatively, you can try sweet and spicy version, with ginger, garlic, chopped onion and honey, for which instructions are here.

Remember! To keep most of the powerful green tea polyphenols in your cuppa, make sure you use warm, not boiling, water, best between 60-80 degrees celsius

Dr. Joanna Michalina Jurek is a postdoctoral researcher at APC Microbiome Ireland at UCC involved in research focusing on nutrition and its impact on human health and overall well-being. Nicola Stanislawska is a high school student from Warsaw, Poland and Founder and Editor in Chief of Innovation Hub.


The views expressed here are those of the author and do not represent or reflect the views of RTÉ