the tea the second most consumed drink in the world, after water. We all know that drinking tea has certain health benefits, but we don't know exactly which ones. And what about the disadvantages, or contraindications We will try to give a good overview here..
On the one hand, let's take an overview of this wonderful beverage to better discover it.
This beverage is obtained from the infusion in hot water of dried leaves from a plant native to Asia, the tea tree, orCamellia sinensis. Note that the fresh leaves of theCamellia sinensis are not consumable. There are four main categories of tea: black tea, green tea, oolong tea, and white tea. The transformation process of the leaves of this plant makes it possible to differentiate them.
Green tea (unfermented)
The tea leaves are not oxidized, but steamed and then dried. Heat prevents fermentation by inactivating enzymes. The absence of oxidation makes it possible to obtain a tea that is paler than black tea. thematcha (See article: Matcha What are the benefits of this wonderful Japanese green tea) is a type of green tea obtained by grinding tea leaves.é.
- Nutritional characteristics:
- One of the richest in polyphenols, including 70% catechins (ex: EGCG).
- Caffeine content, 25 to 45 mg per 250 ml cup of green tea.
Black tea (fully fermented)
The tea leaves are dried under hot air before being rolled and crushed, which triggers fermentation. During fermentation, enzymes naturally present in tea leaves oxidize polyphenolic compounds resulting in changes in color, taste and aroma.
- Nutritional characteristics:
- High content of polyphenols 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 fragrant and flavored (eg jasmine flowers).
- Nutritional characteristics:
- Caffeine content, 25-45mg per 250ml cup of oolong tea.
White tea (unfermented or very little)
Manufacturing process: no or very little fermentation, this is the type of tea that undergoes the least transformation. The leaves of the tea plant are picked and laid out to dry, which leaves the antioxidants present in the leaf intact.
- Nutritional characteristics:
- Slightly higher polyphenol content than green teas.
- Caffeine content, 25 to 45mg per 250ml cup of white tea.
The composition of tea
Tea contains caffeine (theine) and is rich in polyphenols including catechins and theaflavins.
- Catechins are found in greater proportion in green tea thanks to the inactivation of enzymes during the transformation process, 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 transformed into theaflavins.
Finally, these polyphenols are notably responsible for the flavor and aroma of tea and could also have health benefits.
tea and caffeine
Like coffee, tea contains caffeine. The amount of caffeine increases with steeping time, water temperature, and the amount of tea leaves brewed. On average, a 250 ml cup of tea provides 25 to 50 mg of caffeine, less than a cup of filter coffee which contains 80 to 179 mg per cup.
Excessive caffeine consumption can lead to side effects such as difficulty falling asleep, headaches and rapid heartbeat. Therefore, Health Canada recommends that adults consume no more than 400 mg of caffeine per day, which is about eight cups of tea or two to three cups of coffee. As for pregnant or breastfeeding women, they 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 thing to know, the caffeine in tea is not absorbed in the same way as coffee . Tannins and L-theanine, an amino acid, delay its assimilation. It reduces the whiplash effect, but provides gentle stimulation that is spread over time.
Finally, people sensitive to caffeine should avoid tea after 5 p.m. or discard the first infusion water because caffeine dissolves immediately, unlike flavonoids.
Also, they can opt for herbal teas, which do not contain any.
Tea and its benefits
The potential health benefits of drinking tea are mainly due to the polyphenols it contains, which act as antioxidants, among other things.
Green tea and cardiovascular disease
Indeed, in 2020, a systematic review with meta-analysis assessed the relationship between green and black tea consumption and the risk of cardiovascular disease. The results show that daily tea consumption as part of a healthy diet may be associated with a lower risk of cardiovascular disease. Also in 2020, another systematic review with meta-analysis observed the effects of regular consumption of green or black tea on blood pressure in individuals with hypertension or high blood pressure. The results suggest that regular tea consumption may reduce blood pressure, a risk factor for cardiovascular disease.
Green tea and oral health
In addition to the fact that its consumption could reduce the risk of cardiovascular disease, green tea leaves also play a role in oral health.
Indeed, saliva and other oral structures, such as the gums and soft tissues, take advantage of the EGCG present in green tea to neutralize or reduce the damage caused by free radicals.
Not to be overlooked, green tea also contains fluoride, which is absorbed naturally as the tea plant grows. This naturally present fluoride is also a natural antibacterial and increases the resistance of tooth enamel.
The natural antibacterial effect of this plant therefore offers a considerable preventive effect against dental caries (consumed without sugar), gingivitis and could play a preventive role in oral cancers.
Important however not to abuse it, caffeine and fluoride in large quantities can be harmful to the body.
Green tea and weight loss
Although not categorical on humans, a meta-analysis of 11 studies tends to demonstrate a beneficial effect of tea catechins on weight management and maintenance, especially during moderate physical activity.
The principle comes from the fact that both caffeine and catechins increase the concentration of norepinephrine in the body, which would increase energy expenditure through thermogenesis (body heat production) and the oxidation of body fat.
Of course, whether it is consumed in the form of a drink or capsules, it is recommended not to exceed the weekly recommended dose, so as not to damage the liver.
Tea and stomach ulcers
Several studies tend to show that catechins seem to inhibit the growth of the bacteriaHelicobacter pylori. The proliferation of this bacterium in the stomach triggers inflammation, which is responsible for chronic gastritis, which can lead to an ulcer.
Tea vs certain cancers
Several studies suggest that regular consumption of green tea (4-5 cups per day) would be associated with a reduction in certain cancers, more particularly those of the digestive sphere (stomach, esophagus, liver, pancreas and colon), lung, breast, prostate and skin."
EGCG would have the ability to interfere with processes used by cancer cells to grow and invade organs. It would promote their self-destruction and inhibit the formation of blood vessels, allowing their development.
WARNING : conversely, drinking your tea too hot could increase the risk of esophageal cancer. It is better to wait a few minutes to allow it to cool down before consuming it.
Tea vs cognitive decline
Several studies have shown the protective role of caffeine and polyphenols, in particular EGCG, in the onset of dementia and neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases.
And the disadvantages of drinking tea?
- In addition to the presence of caffeine and fluoride which can be harmful if consumed in too large quantities, it would be an ostrich not to think that tea does not 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 flavorings, not natural.
- 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 best to drink your tea at least 1 hour before or 2 hours after the meal.
- Tea would increase the risk of gout attack. People struggling with urinary stones should limit their tea intake to 2 cups a day, while at the same time consuming a food rich in vitamin C.
Discoveries about the benefits of tea evolve over time. Some studies tend to show a positive impact on the prevention of diabetes, or even on the immune system. Let time pass, we should discover more and more over time.
In the meantime, drinking tea is still a great way to stay hydrated and its leaves can also be used to flavor many recipes!
- “Types of Tea. Understanding Food: Principles and Preparation, by Amy Brown, Cengage Learning, 2015, p. 558560..
- Mahdavi-Roshan, M., Salari, A., Ghorbani, Z., & Ashouri, A. (2020). The effects of regular consumption of green or black tea beverage on blood pressure in those with elevated blood pressure or hypertension: A systematic review and meta-analysis.Complementary therapies in medicine,51, 102430. https://doi.org/10.1016/j.ctim.2020.102430
- Chung, M., Zhao, N., Wang, D., Shams-White, M., Karlsen, M., Cassidy, A., Ferruzzi, M., Jacques, P. F., Johnson, E. J., & Wallace, T. C. ( 2020). Dose-Response Relation between Tea Consumption and Risk of Cardiovascular Disease and All-Cause Mortality: A Systematic Review and Meta-Analysis of Population-Based Studies.Advances in nutrition (Bethesda, Md.),11(4), 790814. https://doi.org/10.1093/advances/nmaa010
- https://www.unlockfood.ca/en/Articles/Cafeine/Up to%E2%80%99a-the-last-drop!.aspx
- Green tea and dental health - Center Dentaire St-Lucv (with a particular interest in reference studies)
- Antiobesity effects of green tea catechins: a mechanistic review - PubMed (nih.gov)
- The effects of green tea on weight loss and weight maintenance: a meta-analysis - PubMed (nih.gov)