Tea Demystified - Categories - Benefits - Disadvantages

Alimentation Santé
Le thé démystifié – Catégories – Bienfaits - Inconvénients
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The tea la deuxième boisson la plus consommée dans le monde, après l’eau. Nous savons tous que boire du thé offre certains bienfaits sur la santé, mais sans savoir exactement lesquels. Et qu’en est-il des inconvénients, ou contre-indications?  Nous tenterons ici d’en faire un bon aperçu.

First, let's take a look at this wonderful beverage to learn more about it.

Tea

This beverage is made by infusing dried leaves from a plant native to Asia, the tea plant, or Camellia sinensis. Note that the fresh leaves of the Camellia sinensis are not consumable. There are four main categories of tea : black tea, green tea, oolong tea and white tea. The way the leaves of this plant are processed distinguishes them.

Green tea (unfermented)

Tea leaves are not oxidized, but are steamed and then dried. The heat prevents fermentation by inactivating the enzymes. The lack of oxidation results in a tea paler than black tea. Matcha (See the article: Matcha? What are the benefits of this wonderful Japanese green tea?) is a type of green tea obtained by grinding the tea leaves.

  • Nutritional information :
    • One of the richest in polyphenols, of which 70 % are catechins (e.g. : EGCG).
    • Caffeine content, from 25 to 45 mg per 250 ml cup of green tea.

Black tea (fully fermented)

Tea leaves are dried under warm air before being rolled and crushed, which triggers fermentation. During fermentation, the enzymes naturally present in the tea leaves oxidize the polyphenolic compounds, leading to changes in color, taste and aroma.

  • Nutritional information :
    • High polyphenol content but fermentation leads to oxidation of catechins, which are transformed into theaflavins and thearubigins.
    • Caffeine content: 43 to 50 mg per 250 ml cup of black tea.

Oolong tea (partially fermented)

Tea leaves are partially oxidized and are often scented and flavored (e.g. : jasmine flowers).

  • Nutritional information :
    • Caffeine content: 25 to 45 mg per 250 ml cup of oolong tea.

White tea (unfermented or very lightly fermented)

Manufacturing process: no or very little fermentation — it’s the type of tea that undergoes the least processing. The leaves of the tea plant are picked and laid out to dry, which leaves the antioxidants present in the leaf intact.

  • Nutritional information :
    • Slightly higher polyphenol content than green teas.
    • Caffeine content, from 25 to 45mg per 250 ml cup of white tea.

Tea composition

Tea contains caffeine (theine) and is rich in polyphenols including catechins and theaflavins.

  • Catechins are found in higher proportions in green tea thanks to the inactivation of enzymes during processing, which prevents the oxidation of catechins.
  • As for theaflavins, they are formed during the oxidation of black tea leaves. Indeed, during fermentation, the catechins present in the tea leaves are partially converted into theaflavins.

Finally, these polyphenols are largely responsible for the flavor and aroma of tea and may also have beneficial effects on health.

Tea and caffeine

Like coffee, tea contains caffeine. The amount of caffeine increases with brewing time, water temperature, and the amount of tea leaves used. On average, a 250 ml cup of tea provides 25 to 50 mg of caffeine, which is less than a cup of filtered coffee, which contains 80 to 179 mg per cup.

Excessive caffeine consumption can lead to adverse effects such as difficulty falling asleep, headaches, and an increased heart rate. Therefore, Health Canada recommends that adults not consume more than 400 mg of caffeine per day, which is about eight cups of tea or two to three cups of coffee. Pregnant or breastfeeding women should limit their intake to 300 mg per day, which is about six cups of tea or one to two cups of coffee. In general, when consumed in moderation, caffeine does not cause problems in healthy people.

Good to know, The caffeine in tea is not absorbed in the same way as that in coffee.. Tannins and the L-theanine`, an amino acid, slows its absorption. This reduces the energy spike, but provides a gentle, sustained stimulation over time.`

Finally, people sensitive to caffeine should avoid tea after 5 p.m. or discard the first infusion, because caffeine dissolves immediately, unlike flavonoids.

Also, they can opt for herbal teas, which don't contain any.

Tea and its benefits

The potential health benefits of consuming tea are mainly due to the polyphenols it contains, which act, among other things, as antioxidants.

Green tea and cardiovascular diseases

Indeed, in 2020, a systematic review and meta-analysis evaluated the relationship between green and black tea consumption and the risk of cardiovascular diseases. The results show that daily tea consumption as part of a healthy diet may be associated with a lower risk of cardiovascular diseases. Also in 2020, another systematic review and meta-analysis examined the effects of regular consumption of green or black tea on blood pressure in individuals with hypertension or elevated blood pressure. The results suggest that regular tea consumption could reduce blood pressure, a risk factor for cardiovascular diseases.

Green tea and oral health

In addition to potentially reducing the risk of cardiovascular diseases, green tea leaves also play a role in oral health.

Indeed, saliva and other oral structures, such as the gums and soft tissues, benefit from the EGCG found in green tea to neutralize or reduce damage caused by free radicals.

Not to be overlooked, green tea also contains fluoride, which is naturally absorbed during the growth of the tea plant. This naturally occurring fluoride also has antibacterial properties and helps strengthen tooth enamel.

The natural antibacterial effect of this plant therefore provides a considerable preventive effect against dental caries (when consumed without sugar), gingivitis, and could play a preventive role in oral cancers.

However, it's important not to overuse them; caffeine and fluoride in large quantities can be harmful to the body.

Green tea and weight loss

Although not definitive in humans, a meta-analysis of 11 studies suggests a beneficial effect of tea catechins on weight management and its maintenance, particularly during moderate physical activity.

The principle is based on the fact that both caffeine and catechins increase the body's norepinephrine concentration, which may increase energy expenditure through thermogenesis (the body's production of heat) and the oxidation of body fat.

Of course, whether consumed as a beverage or in capsule form, it is recommended not to exceed the recommended weekly dose, so as not to damage the liver. (see thegreen tea extract for weight loss)

Tea and stomach ulcers

Several studies tend to show that catechins seem to inhibit the growth of the bacterium Helicobacter pylori. The proliferation of this bacterium in the stomach triggers inflammation, which is responsible for chronic gastritis and can lead to an ulcer.

Tea vs certain cancers

Several studies suggest that regular consumption of green tea (4-5 cups per day) may be associated with a reduction in certain cancers, particularly those of the digestive tract (stomach, esophagus, liver, pancreas and colon), lung, breast, prostate and skin."

EGCG may be able to interfere with processes used by cancer cells to grow and invade organs. It may promote their self-destruction and inhibit the formation of blood vessels that allow their development.

WARNING : Conversely, drinking tea that is too hot may increase the risk of esophageal cancer. It's better to wait a few minutes to allow it to cool before drinking it.

Tea vs cognitive decline

 Several studies have shown the protective role of caffeine and polyphenols, notably EGCG, in the onset of dementias and neurodegenerative diseases such as Alzheimer's and Parkinson's diseases.

And what are the disadvantages of drinking tea?

  • Besides the presence of caffeine and fluoride, which can be harmful if consumed in large amounts, it would be burying your head in the sand to think that tea doesn't contain pollutants. Pesticides, herbicides, lubricants, heavy metals, added chemical flavorings... Better to choose a quality tea, and even better an organic tea, without added chemical or artificial flavorings.
  • Tea interferes with iron absorption in the small intestine. For people who may have an iron deficiency (pregnancy, breastfeeding, heavy periods, vegetarianism, inflammatory bowel disease, etc.), it would be preferable to drink their tea at least 1 hour before or 2 hours after a meal.
  • Tea may increase the risk of gout attacks. People dealing with kidney stones should limit their tea consumption to 2 cups per day, while also consuming a vitamin C–rich food at the same time.

Discoveries about the benefits of tea evolve over time. Some studies tend to show a positive impact on diabetes prevention, as well as on the immune system. Let's give it time; we should keep discovering more and more.

In the meantime, drinking tea remains an excellent way to stay hydrated, and its leaves can also be used to flavor many recipes!

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Tags: Alimentation, Santé

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