Tea is one of the most widely consumed beverages in the world, with many different types of tea available. According to sources, it was consumed in China as early as 2700 BC. Today, tea is consumed in almost every country. Green tea also comes from China, from a plant called Camellia Sinensis. White, black and oolong tea also come from this plant, with the brewing and fermentation methods varying from tea to tea.
The main active ingredients in green tea are catechins, a group of polyphenols, and caffeine. These catechins have strong antioxidant properties that protect against substances that damage cells (reactive free radicals). The most promising of the catechins is EGCG (epigallocatechin-3-gallate).
The polyphenols in green tea can have a number of beneficial effects on our bodies - most of these are due to the antioxidant properties of EGCG.
UV radiation is also very important for vitamin D production. In excess amounts it can have cell damaging effects, UV radiation can also have a direct cell damaging effect (by causing some molecules within cells to absorb excess energy and thus change their structure - photodimerisation) or trigger free radical production which further damages cells. The first line of defence against UV radiation is melanin, a particular substance that releases UV radiation as heat. However, excessive melanin production will also trigger free radical production, so our body cannot protect itself properly against excessive UV radiation. Due to the anti-free radical properties of EGCG in green tea, which can help protect the skin, there have been several studies confirming that green tea extract or supplementation of green tea on the skin reduces skin damage caused by UV radiation.
EGCG is able to cross the blood-brain barrier that protects the brain and thus can also act on the nervous system. Studies have shown that it can stimulate brain function - this effect was most significant when EGCG, caffeine and L-theanine were combined - fortunately, green tea is rich in all three. More importantly, EGCG also has neuroprotective properties, which may reduce the chances of developing many neurological diseases (such as Alzheimer's). This effect is due to EGCG's antioxidant activity and its cell renewal (autophagy stimulating) effect. During autophagy, cells self-degrade damaged elements to replace them with new, healthy cell components.
EGCG also has an effect on immune cells, stimulating the function of many immune cells - it has a significant effect on Natural Killer (NK) cells. Some immune cells sense invaders (infection, foreign substances) and NK cells negate them - we should think of NK cells as the bouncers. NK cells are also responsible for killing cancer cells, among other things. In this way, green tea extract also has immune-boosting and anti-tumour effects.
The catechins in green tea are able to inhibit an enzyme necessary for the production of cholesterol, thus it may have high cholesterol-lowering effects.
Catechins in green tea may also exert anti-microbial effects, indirectly by boosting immunity and reducing inflammation. However, directly, they have cell wall damaging effects against bacteria and viruses. The anti-mouth odour effects of green tea can also be attributed to its microbial properties.
Vitamin C and fish oil (Omega 3) can enhance the benefits and effectiveness of green tea. Ascorbic acid (Vitamin C) shows synergism with EGCG (as well as with another tea component, theflavin) in suppressing adenocarcinoma proliferation.
In addition, green tea extract has fat burning effects, the effectiveness of which depends on the dose used. Caffeine and ephedrine are the real fat burners, green tea can help catechins to feel better (as both stimulate adrenaline production and green tea extract stimulates the time adrenaline spends in the body (until it is broken down). However, in the long term, too much caffeine intake will lead to adaptation and in such cases neither green tea extract nor caffeine will work properly - watch the dose.
The effects of green tea extract on fat loss have been shown in doses of 400-500 mg. Its health effects may also be seen at lower doses (200-250 mg).
Green tea catechins up to 800 mg daily intake are considered safe. But be aware that supplements can contain up to 600 mg of caffeine, so be sure to consult a doctor before taking them. In one study, 1200 mg of EGCG was also found to be well tolerated, but there was a significant increase in nausea and vomiting.