Green Tea – Camellia sinensis
Black, Oolong and Green tea all stem from the same plant, Camellia sinensis, however differences in processing results in three very distinct products not only in taste but also in health benefits. Green tea is the least processed and therefore isn’t exposed to oxidation, resulting in a tea that retains more antioxidants. The specific antoxidants found in green tea include catechin, epicatechin, epicatechin gallate, epigallocatechin gallate and proanthocyanidins.
In different parts of Asia, the tea is harvested at different times according to tradition. In Japan, only one cultivar of Camellia sinensis is used, the Yabukita variety, and the leaves are harvested any time from late spring all the way through until autumn – giving the leaves more time to grow on the plant. In contast, in China, many varieties are used and the green tea is only harvested in the early spring, meaning the leaves have less time to grow. Not only the leaves are plucked, but in China the spring buds of the plants are also harvested. The Chinese method of drying the leaves uses a pan to dry fire them, or they might be oven dried or dried under the sun. The tea is then hand processed with workers rolling the tea leaves into shapes – such as balls, twists, spirals and swords. Green tea is traditionally only brewed for 2-3 minutes and if you leave it longer it can be quite bitter and higher in the astringent tannins.
Some Japanese Green Tea can also contain twigs and roasted puffed rice along with the green tea, the popular variety is referred to as Genmaicha. Kyoto was the birthplace of genmaicha, where legend tells of a tea farmer who mixed roasted brown rice (as a filler) in with his cheapest blends of green tea so that even poor people could afford to buy his tea, and get some extra nutrients along with the tea. Genmaicha has a milder nutty flavour combining the fresh grassy flavor of green tea with the aroma of the roasted rice and it became a popular brew in time. Tea steeped from genmaicha has a light yellow hue and It is traditionally brewed for 3-5 minutes.
What it’s good for
Green tea contains a potent range of antioxidants responsible for fighting a prime culprit in the ageing process; free radicals. Epigallocatechin gallate, a green tea polyphenol now incorporated into many skin care formulations, has been shown to reduce damage done to skin cells and is proported to offer antioxidant protection against mild sun exposure. To learn more about natural sunscreens, includling a recipe that includes green tea in it, please click here.
Green tea has been shown in several studies to decrease proliferation of cancer cells and it can also increase apoptosis, which is what we call the highly regulated process of inbuilt cell death. Many cancer cells lose their innate programming for cell death and thus keep growing and spreading. Agents that can stimulate this process of apoptosis can lead to reduced cancer cell numbers. Epigallocatechin gallate was found to reduce the risk of skin cancer through its protection against UV radiation. Topical application of green tea half an hour before skin exposure was shown to be protective against sunburn. Systematic scientific studies and research suggest green tea possesses protective capabilities against breast, prostate and upper gastrointestinal tract cancers.
Green tea consumption has been associated in several studies with moderate weight loss, reduced weight circumference and metabolic parameter improvements when combined with regular exercise. Animal studies found this weight loss to be due to decreased leptin (dubbed the obesity hormone), decreased food intake and an increase in metabolic rate due to increased thermogenesis. Green tea also contains caffeine which has a subtle stimulating impact on weight loss, but usually not strong enough on its own to exert much impact.
Memory and Mood
Green tea intake has been shown to significantly improve cognitive performance and learning ability with long-term consumption. This is thought to be due to a combination of improved cerebral blood flow and the neuro-protective effects of L-theanine, a compound found in green tea. L-theanine exerts this action through modulation of our neurotransmitters GABA and glutamate. Despite these neurotransmitters being cut from the same cloth, GABA and glutamate have opposing effects in the body. Glutamate is an excitatory neurotransmitter and is often released by the body in times of stress. GABA on the other hand is an inhibitory neurotransmitter and when released has a calming effect on the body. L-theanine works by blocking the glutamate pathway, in turn increasing GABA. Incorporating green tea into your diet is a nice way to gently reduce the effects of glutamate but for those suffering from anxiety and stress a supplemental dose of L-theanine would be more beneficial. I have found using an actual capsule of concentrated L-theanine can be an effective supplement for anxiety and tension in my patients.
What it’s not good for
- Due to its caffeine content, high intake of green tea may increase central nervous system (CNS) stimulation of drugs such as nicotine and salbutamol and conversely reduce drug effects of CNS depressants such as benzodiazepines.
- Green tea contains high amounts of tannins that are capable of binding to and reducing the absorption of iron and other minerals. Caution in iron deficiency and iron supplementation should be exercised.
- Caffeine content of green tea may effect blood glucose, monitoring in diabetes is advised
- Due to its caffeine content, green tea may exhibit a diuretic effect, so ensure you drink an extra glass of water for each cup of tea consumed.
Here is a guide to all the different types of green tea with some of the benefits and highlights to choose from when selecting the best one for you.
Excessive intake of anything, even something that is seemingly good for you, is indeed not good for you. Drinking 3-4 cups of green tea per day is sufficient to get the beneficial effects according to the research. I also recommend combining green tea with other herbal teas that can have additional medicinal benefits for your individual needs.
Drinking very high doses of any caffeinated beverage including green tea is unsafe and can cause major health issues due to caffeine content.