The risks associated with green tea are the same as those associated with any other kind of tea (common black tea, White Tea etc.) and are primarily due to the content of caffeine and tannin. The contraindications may vary with the percentage of caffeine and tannins in it. Most people might be familiar with these adversities, but it is still important to review and summarize the components responsible, as well as the associated risks.
"Drink tea if you enjoy it, in moderation, and not because you're taking it as a medicine," says Dr. Sesso. Stirring in a little sugar is fine, but if you add a few heaping teaspoons of sugar, you're probably canceling out tea's possible benefits, he notes. And beware of the sugar found in many bottled teas, some of which contain as much as nine teaspoons of sugar per serving—almost as much as colas and other soft drinks. Check bottled tea labels and choose only pure, unadulterated tea—or save money and brew your own at home.

The reason that green tea has more health benefits attached to it than black tea is due to the processing. Black tea is processed in a way that allows for fermentation whereas green tea’s processing avoids the fermentation process. As a result, green tea retains maximum amount of antioxidants and poly-phenols the substances that give green tea its many benefits.
Jump up ^ Iswaldi, I; Arráez-Román, D; Rodríguez-Medina, I; Beltrán-Debón, R; Joven, J; Segura-Carretero, A; Fernández-Gutiérrez, A (2011). "Identification of phenolic compounds in aqueous and ethanolic rooibos extracts (Aspalathus linearis) by HPLC-ESI-MS (TOF/IT)". Analytical and Bioanalytical Chemistry. 400 (10): 3643–54. doi:10.1007/s00216-011-4998-z. PMID 21509483.
Because you’re consuming whole leaves in matcha, you may get three times as much caffeine than a cup of steeped tea, about the amount in a cup of brewed coffee. Matcha aficionados say that compared to the caffeine buzz from coffee, matcha creates an “alert calm” due to a natural substance it contains called l-theanine, which induces relaxation without drowsiness. Still, I do believe it’s best to nix all forms of caffeine (including matcha) at least six hours before bedtime, to ensure a good night’s sleep.

Rooibos tea or red tea is an herbal beverage, with medicinal properties, that is acquired from the Aspalathus linearis bush plant found in South Africa. According to the South African Rooibos Council, rooibos is not a true tea, but an herb. The fermented tea is red in color. The health benefits of red rooibos tea are abundant. It is popular due to its great taste and unique color that comes along with health benefits.
Shade grown: All matcha is made from shade-grown tea leaves—a labor-intensive process where tea bushes are protected from the sun and light is filtered to the bushes in a very controlled manor. Shading boosts the chlorophyll production in the plant, giving the leaves a rich green color. The lack of sun reduces the plant’s photosynthesis of the leaves, which in turn alters the naturally occurring levels of caffeine, flavanols, sugars, antioxidants, and theanine. By controlling the sun exposure, tea producers can significantly alter the chemical make-up and flavor of the final tea leaves.