Modern medical research has demonstrated the many health benefits of green tea: a drink made from the leaves of the tea plant (Camellia sinensis).
Tea is the most consumed beverage in the world after water and has been in use for over 500 years. Much of its benefits have been attributed to a number of potent antioxidants found in the tea leaves called polyphenols. These substances are also present in other plant foods like cocoa.
More recently, however, researchers have focused on its unique, amino acid called theanine. It accounts for tea's relaxing while energising effect and medicinal benefits. Theanine is the predominant amino acid in green tea leaves and gives tea its characteristic taste.
THEANINE for STRESS
Containing small quantities of natural caffeine, green tea has a calming effect due to theanine. It balances the stimulatory effects of caffeine on the nervous system.
Theanine creates a sense of relaxation in approximately 30 to 40 minutes after ingestion by two actions. First, it stimulates the brain's electrical activity to produce alpha brain waves. This creates a state of relaxation and mental alertness similar to that achieved through meditation.
Second, theanine influences the brain's chemistry to increase the levels of two neurotransmitters, dopamine and serotonin. These important brain chemicals produce feelings of well-being and relaxation.
People under stress may use theanine to alleviate its negative effects without becoming sedated, as theanine doesn't make one drowsy.
Theanine for Learning and Concentration
Theanine enhances the ability to learn, remember and concentrate - a reason why historically, monks and scholars have incorporated tea drinking as an aid to meditation and study.
It seems to be even more effective when you are stressed and your mind is preoccupied by many thoughts by allowing you to focus on the task at hand. A 2007 study found that it even synergises with caffeine to boost the activity of brain cells.
Researchers found that as little as 100 milligrams of theanine enabled people to focus better on complicated tasks, when consumed with 60 milligrams of caffeine, a combination found in roughly four cups of green tea.
Theanine and cancer
A 2002 study published by Sadzuka, et al found that theanine may help improve the quality of life of cancer patients by improving the efficacy of cancer drugs, and through its relaxing effects.
Theanine increased the concentration of anti-cancer drugs in tumours while reducing the levels of anti-cancer drugs in the healthy tissues, where they are not needed. This served to improve the effectiveness of the treatment while decreasing its side effect. Theanine itself also inhibited the growth of cancer tumours.
Surveys in Japan, where green tea is very popular, showed green tea drinkers had a much lower incidence of liver, pancreatic, breast, prostate, lung, oesophageal and stomach cancer.
Theanine for Blood Pressure and Cholesterol
Japanese researchers report that theanine reduces high blood pressure, but has no effect on normal blood pressure. Theanine was also found to reduce cholesterol levels in humans, and prevent good cholesterol from turning bad through oxidation.
THEANINE increases IMMUNITY
Studies at Brigham and Women's Hospital and Harvard Medical School demonstrated that theanine increased the body's immunity against colds and flu and can promote a strong immune response.
THEANINE for WEIGHT LOSS
Green tea helps with weight loss, and according to a 2004 Japanese study, theanine contributes to this effect. In this research on animals, theanine administration lowered body weight, body fat and triglycerides (blood fat).
SIDE EFFECTS
Green tea, even in large amounts, is associated with very few side effects. Staining of the teeth is probably the commonest problem. Using a toothpaste containing bicarbonate and hydrogen peroxide can prevent this.
You may email Dr Tony Vendryes at vendryes@mac.com or listen to An Ounce of Prevention on POWER 106FM on Fridays at 8 p.m. The programme streams live on the Internet.