In sum, the answer for most people is an unequivocal YES -- green tea is one of the safest substances on the planet. Matcha has been used for medicinal purposes (and spiritual purposes, with its origins in zen buddhism) in Japan for more than a thousand years. It's hard to imagine a safer food to ingest.
Matcha does have small amounts of caffeine. How sensitive are you to caffeine? The Mayo Clinic says that an average adult can safely tolerate about 400mg of caffeine daily. That's about 2.5 cups of brewed coffee, but it's a whopping 16 servings of matcha (a gram of matcha is considered a serving, and it contains about 25mg of caffeine). Energy drinks, soft drinks, chocolate ... all contain caffeine, and I think we can agree that matcha's many health benefits mean that it's whole lot better for you than those. For people who cannot tolerate any caffeine whatsoever, matcha is not their drink.
Another issue that people ask about is lead; there are lots of stories on the internet about lead levels in matcha being potentially dangerous, since the whole leaf is consumed. Studies that found lead were all from matcha that came from China, which isn't surpising considering China's general lack environmental protections. But it simply isn't true for matcha that comes from Japan (all of Breakaway Matcha's teas come from Japan).
What about people with high blood pressure? Many Japanese doctors recommend matcha for patients with high blood pressure. Matcha tends to thin the blood and opens up the walls of your arteries. More blood streaming through, more easily, lowers blood pressure.
And the Fukushima disaster? Do we need to be concerned about radiation? No. If you are very sensitive to caffeine, you might consider matcha as an excellent alternative to coffee and even other teas. We've tested for cesium and other radiation every year since the 2011 Fukushima accident, and we’re clear.
Needless to say, everyone has different biological needs. You should always consult your doctor before making big changes to your diet and lifestyle. But you'll be hard-pressed to find a safer food than our matcha.