Indian tea is Camellia Sinensis var. Assamica. Without getting into that, tea is one of the healthiest things anyone can have. If you want to get into the idea that it can poison you, yes. It can. So can caffeine, sugar or water. (a woman died from drinking something like 12 cups of water in under a minute)
"Everything in moderation"
This applies to tea as well. Tea contains something called oxalate which can damage one's kidneys if taking in large amounts. And by large amounts, I mean 16 or 20 cups of black tea every day. 2 cups a day is wonderfully healthy, good mix of oxilate and vitamin C.
See there have been those articles of speculating that tea is unhealthy. Being a person of science, I can't help but want to know the source of information, whether or not I already believe in it. Being told by someone that it is poison wouldn't do it for me. Why does this person say it's poisonous? Where did he hear that from? What were the primary sources for this information?It's helpful to remain skeptical in this day and age of widespread information. And misinformation, ie "fake news."
But yes, in excess tea can be poisonous to the body. Usually black tea. But if I have to choose over which I consider "poisonous" I would say the coffee which is much heavier in caffeine than tea. Caffeine can cause physiological dependence and sometimes psychological. I would hate to be like an old friend of mine who would start shaking and get headaches if she didn't have at least one cup of coffee everyday.
Aaanyhoo, my brother is a coffee addict too. It's all just down to preference, but claiming it is poisonous and I can't help but be skeptical