Tea is one of the most widely consumed drinks. It is taken primarily as a hot drink for its stimulating effects. One feels refreshed after drinking it and gets over his tired feelings. This reputation leads to tea drinking habit which in course of time becomes deep rooted and difficult to give up.
The most active alkaloid principle in tea is caffeine. This is an addictive drug as it stimulates central nervous system. The effects are short lived but withdrawal symptoms observed are lethargy, headaches, anxiety, irritability and insomnia. All this shows that this is a quite strong drug which could lead to potential health problems.
Tea is prepared from leaves of shrub belonging to camellia family. The plant is a native of south east Asia. The earliest record of its cultivation comes from China in 4th century AD.
The chemical composition of tea leaves are as follows:
- Moisture: 5 – 8%
- Aromatic oils: 0.5%
- Caffeine: 2.5 – 5%
- Nitrogen: 4.75 – 5.5%
- Soluble substances: 38 – 45%
- Tannin: 7 – 14%
- Minerals: 5 – 5.75%
The primary effects of tea are due to alkaloids, caffeine, tannin and aromatic oils. It is not only composition of tea leaves that is harmful but also the composition of infusion which is prepared by boiling tea with water.
The harmful effects of drinking excessive tea in case of specific diseases are as summed below:
Indigestion: Tea is said to slow down digestion. It impedes the action of ptyalin, a digestive ferment of saliva which acts as cooked starch. Tannin is responsible for inhibition of this condition. This effect could however disappear once milk is added as milk precipates tannin. Tea also delays stomach digestion and could lead to gas formation diarrhoea and constipation.
Kidney disorders: Experiments show that 5 cups of tea increases the urine by 400 – 500% in people vulnerable to kidney related ailments. This continued stimulation of kidneys by caffeine might damage them. Tea could also promote kidney stone because of its high concentration of oxalate.
Premenstrual syndrome: Drinking tea could aggravate symptoms of premenstrual syndrome . According to a research conducted under Dr Annette Rossignol, an associate professor of public health at Oregon University, women in China who drank between 1 – 4 cups of tea a day were twice as likely to have PMS then non tea drinkers. drinking 8 cups of tea increased the PMS occurrence 10 times.
Incontinence: Drinking too much tea could lead to incontinence or frequent/urgent impulse to urinate. According to a recent study conducted at St. George’s Hospital London, caffeine could exert pressure on bladder by causing muscle surrounding it to contract increasing the need to urinate.
The respiratory and cardiac muscles are also stimulated by caffeine as coronary arteries get dilated resulting in the increase in the rate of blood flow. The quickening of respiration lowers the level of carbon dioxide and increases the heat production of body by 10 – 20%.