Both nutritionists we spoke to agree that drinking tea when you wake up and before bed can help your system rev up and calm down, depending on which variety you choose. If you’re a tea fanatic, work in a few cups throughout the day: Unless you’re sensitive to caffeine, you can probably handle five to seven cups a day without any negative side effects, says Lagano.

Along with caffeine, which gives green tea its characteristic taste, bitterness, and stimulating effect, green tea is also rich in a group of chemicals, called catechin polyphenols (commonly known as tannins, which contribute to bitter taste and astringency). These catechin polyphenols include catechin, epicatechin, epicatechin gallate (ECG), epigallocatechin gallate (EGCG), and various proanthocyanidins. They are also known as flavonoids and are very powerful antioxidants. Flavonoids, together with some amino acids like thiamine, are responsible for the potent flavor of green tea.
We believe that if you’re going to do something, you should do it right. That mentality took us around the world in search of the best Matcha. We eventually landed in Japan, where we found some of the brightest green powder we had ever seen. Japan has warm weather, and receives plenty of sunlight and rain — all of which make it an ideal climate in which to grow leaves.
This best-selling detox tea has a loyal following, with thousands of reviewers claiming that it helped with excess bloating, daily digestive issues, and ultimately contributed to weight loss when consumed alongside a balanced diet and regular exercise. Made with green tea leaf, matcha green tea, and guarana seed, this tea blend is quite caffeinated — so don't sip it before bedtime. 
There are three main varieties of tea: green, black, and oolong. All three varieties are made from the leaves of the same species of plant called Camellia sinensis; the difference is in how the tea leaves are processed. Green tea is made from unfermented leaves, while oolong tea is made from partially fermented leaves and black tea is fully fermented.
Grown under shade for three weeks prior to plucking, gyokuro is one of the most exclusive varieties of tea produced in Japan.[60] The shading technique imparts a sweeter flavor, and produces a particularly rich color thanks to the higher amounts of chlorophyll in the shaded leaf. Gyokuro tea is associated with the Uji region, the first tea-growing region in Japan. It is often made using smaller-leaf cultivars of the tea plant.[61]