As for green tea, I'm not too sure about it. First of all, does it have enough caffeine in it to be harmful? Secondly, I've heard that it can cause some people to lose their hair. Mine is already getting pretty thin, and I don't want it to get any worse (This could be caused by other things as well). Lastly, I've heard that it contains fluoride and that this can be a problem for the thyroid. Is this true, or does it depend on the type of tea that you get? So my question is, has anyone heard of these concerns?
I've not heard of any of those issues concerning green tea. Billions of people in Asia have been drinking green tea for thousands of years--apparently without experiencing any serious harmful effects. I've always understood green tea consumption to be considered healthy (or at least not harmful). Maybe you're thinking of some other type of tea? Or maybe a green tea supplement (which I wouldn't use)?
Regarding caffeine, I believe green tea has less caffeine than regular tea or coffee. If you want the healthiest green tea, buy an organic variety; although, I don't think this is necessary.
Personally, I don't think you should spend too much time concerning yourself with this issue. If you like your caffeine buzz and you enjoy a hot beverage, then see if tea works for you. If you want it sweet, then you can try stevia; although, my advice is to go cold turkey and drink your hot beverages without any sweeteners. Just tough it out for a few days; you will eventually begin to enjoy the natural taste of whatever beverage you're drinking.
Dr. McDougall's take on tea http://www.youtube.com/watch?v=cobFlRRCG_g