As a master herbalist I'm a little wary of hopping onto the bandwagon when an herb, fruit or vegetable starts getting popular. Without it has been studied a great deal claims made for them are pretty unsubstantiated, no matter what the hype.
Green tea has been studied a great deal. It does have benefits and it does have drawbacks. Knowing both sides is the best way to find out if it will work for you.
The Good : The caffeine content of green tea can boost the metabolism. It is used in weight loss products for that purpose and it is one of the few I suggest to clients when asked about that sort of supplement.
A 2004 study of Chinese tea drinkers reported that a half cup of green or oolong tea per day cut high blood pressure by 50%. A constituent of the tea, called a flavonoid is thought to be responsible. This study sums up the theory that there was a connection that had been going on for many years.
The Bad : To get enough green tea to rise metabolism requires at least twelve cups. That's why they are in supplement form. It's rather hard to drink twelve cups of anything in one day and it would probably be hazardous due to the amount of fluids required.
According to the Mayo Clinic, caffeine can raise blood pressure a great deal fairly quickly. It is temporary as long as it's limited. If someone drinks fluids with caffeine constantly that may make readings higher all of the time. There are people that develop an immunity to the caffeine and it is not a problem. If you have been diagnosed with this medical condition you may want to consult your doctor about caffeine take.
The Compromise : There are doctors that will say outright that you should avoid all caffeine. On the other hand, some doctors are willing to see which way your body will go with the tea, because it does have health benefits. You may be asked to buy an inexpensive blood pressure kit and take daily readings. This will determine if you need to cut back, quit or that you are fine.