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Tea and health
Since it first appeared in Asia, tea has been considered beneficial for the body. The oldest references to tea come from historians advocating its medicinal properties. Tea was first used in the form of a paste, as a poultice to combat rheumatism. Legends about tea, whether Chinese, Indian or Japanese, all show, in their own way, the stimulating and invigorating properties of tea. The Emperor Shen Nung, father of Chinese medicine and farming, states in his Medical Book that "tea relieves tiredness, strengthens the will, delights the soul and enlivens the sight."
In the 20th century, medical science allows us to understand scientifically the many benefits that tea drinkers have known empirically for over two thousand years.
Everything you need to know about:
Tea and Caffeine
There are three xanthics present in tea: caffeine, theophylline and theobromine.
These are organic substances found in all types of teas, whatever their color.
This is the main xanthic in tea and represents 2% to 3% of the dry leaf. It is important to realize that caffeine found in tea and coffee is one and the same molecule, the only difference being that it is proportionately more present in coffee.
The caffeine content of a tea depends both on the leaf used - the bud and the first leaf contain twice as much as Souchong leaves - and on the season of the harvest, since climatic variations influence the maturity of the leaf.
Some teas are therefore high in caffeine, such as new season crops and those with many buds, while others are almost entirely caffeine-free, such as smoked teas and Wu Long (Oolong) teas.
Caffeine is a strong stimulant to the nervous system. Unlike coffee, the caffeine in tea is released slowly into the body. For this reason, it allows us to stay awake and alert without becoming hyper. This makes tea the ideal beverage to accompany exercise, both mental and physical.
While this stimulating effect can cause a slight tendency towards insomnia in sensitive people, it is very easy to "decaffeinate" one's tea at home without altering the flavor. Because the caffeine in tea is a constituent which is released in the first few seconds of infusion, simply rinse the leaves with a first pouring of boiling water, leave for about thirty seconds and then discard the water.
Theophylline is present in much smaller quantities than caffeine. Its function is essentially that of vasodilation, which means that it helps to dilate the veins and blood vessels, improving blood circulation. This explains why tea, whether ice cold or boiling hot, is a refreshing drink, since vasodilation is one of the mechanisms that contribute to the thermoregulation of the body's temperature. Theophylline is also a respiratory stimulant which is used in certain medicines for the treatment of asthma. However, tea should under no circumstances be considered a remedy for this type of complaint.
This xanthic, which is found in lesser quantities than the previous two, has a strong diuretic effect. By stimulating renal circulation, it encourages evacuation though the urinary tract.
Tea and tannins (or polyphenols)
Tannins in tea are similar substances to the tannins found in wine, both of which have very similar properties. Some characteristics of tea, like its color, body or strength, are directly dependent on these polyphenolic derivatives and on the changes they have undergone. It is easy to recognize a tea that is high in tannin by the astringency of the drink, which sometimes causes bitterness if the tea has been over-brewed. Tannins are released slowly but with increasing intensity, which means that an overly long infusion considerably raises their concentration and makes the tea bitter. Astringency plays a role in the tightening of cell tissue. Used externally, tea can be added to a bath to close and tighten pores, or in the final rinse when shampooing the hair to make it smooth and shiny.
The main polyphenolic derivatives of tea are catechols and flavonoids. Their effect on the human body has been particularly highlighted by research into green teas. The reason for this is that most scientific studies in this area have been carried out in Japan, a country that produces only green tea. However, in recent years this study has been extended to include other families of teas, including black teas, Wu Long (Oolong) teas and dark teas. While tannins are present in different types of tea, the fermentation process alters them and the effects of polyphenols in non-green teas are still not well understood by researchers. Are they the same or are they different from those in green teas? We will have to wait a few more years before we have the answer.
Scientific research has revealed that polyphenols have an effect on bad cholesterol. Thus a daily intake of 5 cups of tea over a few months leads to a lowering of LDL-cholesterol - "bad" cholesterol, as opposed to HDL-cholesterol.
Other studies have further explored this matter and have highlighted the effects of green tea in the prevention of cardiovascular disease, especially arteriosclerosis, an arterial disease associated with hardening of the arteries and fatty deposits.
One digestive effect of polyphenols has been demonstrated: drinking green tea limits the absorption of fats during digestion. So a cup of tea taken at the end of a meal, about 40 minutes afterwards, will aid digestion by activating a process of fat elimination.
Numerous scientific theories pertaining to the antioxidizing effects of polyphenols have also been tested. Polyphenols, which are present in considerable quantities in fruit, vegetables, red wine and green tea, play a vital role in the fight against the free radicals that are responsible for cell aging. One of the polyphenols in green tea - epigallocatechol gallate - is the object of very detailed scientific research into the fight against the development of cancerous cells. This polyphenol might inhibit the actions of the enzyme urokinase, which is responsible for the random multiplication of cancerous cells.
At the present time, this research has been tested only on animals, and the same results still need to be proven for man in order to establish a link between tea consumption and the prevention of certain cancers. It should be added that this research is not, in any way, taking place within a therapeutic framework, but only in terms of preventative dietary guidelines.
Tea and vitamins
The tea plant is naturally high in vitamin C (about 250mg per 3.5 oz / 100g of fresh leaves). Unfortunately, it is completely destroyed from the minute the tea is infused in water at a temperature above 86°F / 30°C. Tea cannot, therefore, be used as a source of vitamin C. On the other hand, flavonoids, one of the tannins found in tea, help promote the body's absorption of vitamin C.
Tea contains a considerable amount of vitamin P, which increases capillary strength and shortens bleeding time.
B group vitamins
Highly soluble in water, many B vitamins are found in a cup of tea. They contribute to the general good health of the human body by kick-starting the metabolism, in other words the whole series of reactions that take place within our organic tissue, such as energy output, nutrition, assimilation and so on.
Tea and iron
It is often said that drinking tea lowers iron levels in the blood.
Indeed, the tannins present in tea, while being very beneficial to the body on many counts, do have one drawback: they prevent the iron contained in foods from being fully absorbed by the body during digestion. A heavy daily consumption of tea (more than 50 fl oz / 1.5 liters) could have an effect on the body's absorption of iron. This does not pose a problem if the tea drinker does not suffer from an iron deficiency and has a well-balanced diet. If this is not the case, it is recommended to wait 40 minutes after meals before drinking tea.
Iron absorbed by the human body is found in red meats and, to a much lesser extent, in vegetables. A vegetarian therefore has a greater risk of iron deficiency. Pregnant women are also more at risk, so during this period it might be better to limit tea consumption.
Tea and mineral salts
Tea is rich in potassium and fluoride. It is also low in salt, which makes it perfectly suitable for salt-free diets.
The importance of fluoride in the fight against dental cavities is well known. Tea contains 0.3mg of fluoride per cup. Since we know that we need to absorb 1mg of fluoride per day to protect our tooth enamel, tea can be an effective contributor if taken regularly.