Caffeine: Everyone knows that caffeine is an external stimulant and raises blood pressure, and is actually toxic in nature (it may be fatal for some animals). Caffeine is also addictive and can have adverse effects on the liver and internal organs over the course of many years. That being said, it is the component of tea which makes it energizing and refreshing, which is why people are willing to risk it.
There are also several harmful effects of green tea over-consumption that are possible. These include consuming tainted supplements marked as green tea extract, high caffeine consumption, consuming aluminum, and the effects of tea polyphenols on iron bioavailability. Green tea extracts should not be taken by patients suffering from renal failure, liver disease, heart conditions or major cardiovascular problems without supervision from a doctor. People sensitive to caffeine should be careful of their intake. Pregnant and breast-feeding women should drink no more than one or two cups per day, as some research shows that more caffeine than this amount may interfere with normal heart rhythms.
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.