Don't forget "coffee" isn't just caffiene. It has other ingredients as well. That is part of the problem with drug companies and many scientists now of days. They always look at some sort of "magic ingrediant" and isolate it then wonder why it doesn't work as expected.
All natural chemicals work in tandam with each other to create whatever effects the natural plant or seed (etc.) has. As an example, just as Thujone in Absinthe is supposed to be just the wormwood. Herbs don't work that way. It is a combination of herbs that create the effect Absinthe has. Not just the wormwood. The same can be said for cannibas, tobacco, etc. etc. etc.

So, when you drink coffee you are getting more than just the caffiene.
I am not trying to rant here, but as an herbalist, the drug companies have been trying to brain washed the public (and has mostly succeeded) in saying "one" ingredient is what is needed and that THEY have isolated it and it works. Then later we ALWAYS find out different. Why? Well, the all might dollar and, at least here in the U.S., a bought FDA and all government in general. No, I am not going off the deep end. I am being realistic. It's all relative.

Now with that out of the way, let me say that just about anything is just fine for you (I'm generalizing here folks), depending upon your own (and I must point out) - individual- body chemistry. That is why a drug will work for someone and not someone else or the effects are different from person to person. Every single drug and herb on this planet works this way.
Anything you take is just fine as long as it is done in moderation for your body. This is your responsibility to know what is and what isn't. Not the governements or the drug companies.
Moderation is the key. Some people can drink loads of coffee without hardly any effects where the same amount may send another person reeling.
If you like coffee and it works for you, try to a glass of water with your coffee. I love coffee and drink a lot of it. I know that as much as I drink isn't exactly "good" for me, but when I go out to eat and I get coffee that just isn't right, I drink a glass of water with it and I try to know my limits. If not, my body will tell me that I've had enough. If I choose not to listen then it is my own fault that I end up feeling the wrath.