The evidence surrounding caffeine effects can be confusing.  In my opinion, many studies as well as case studies and anecdotal evidence show moderate caffeine consumption is OK, maybe even beneficial.  You should focus more on where your getting your caffeine.

A couple of points:  first of all, caffeine - by definition - is a drug.  It and it's derivatives have been used for a long time to treat certain diseases states like asthma.  Secondly, and this is on a personal note, the effects of caffeine to me have been put too much in the spotlight.  I'm more concerned about 'how' people are getting their caffeine and how much of it they are getting.

What do I mean?  Simple...caffeine itself can be good or bad depending on how much you take.  When caffeine gets into your body one of it's first actions is to dilate blood vessels.  Well, this can be good as it can increase blood flow to your brain and allow the 'fog' to lift so you can think clearer.  But, at higher doses it can cause the jitters.  Also, it can lead to changes in blood pressure and heart rate.  Obviously, in folks with preexisting heart conditions this is concerning and they should follow their doctors orders regarding caffeine intake.

So, you can think of the effects of caffeine like a good versus evil sort of thing.  In moderation caffeine can be beneficial in many populations.  But, get carried away and the side effects begin to show up.

Caffeine Sources

The second, and often overlooked point, is where are you getting your caffeine from?

My main source is my morning cup (yes, 1 cup) of fresh ground, black coffee.  However, if your source is soda than I would stop immediately.  Soda may be one of the most harmful substances on this planet.  And no, diet soda isn't any better.  Normally, most folks mistakenly think that the 'diet' in front makes it better.  It doesn't.  It's loaded with substances that mess with your metabolism, insulin secretion and may even increase your risk of osteoporosis (from phosphoric acid, which is also contained in milk).

In my opinion, coffee and tea in moderation are just fine.  I've tried tea, but it's doesn't agree with me in the morning.  And, for many years I went without both.  But, I've found that I really enjoy a nice cup of dark coffee to start my morning.  Also, as a writer, I find it makes my work more productive first thing in the morning - particularly since I'm up at 4:45AM every day.

Yes, there are studies showing detrimental effects from caffeine.  But nearly any scientist could go in and find fault with these studies.  For me, most people in most studies have terrible eating habits.  But the studies still make a link to disease states without looking at (or controlling) the most likely link: nutrition.

Also, many folks who live quite long and healthy lives (yes, I realize these aren't 'clinical studies' but that is only because this population of people is so small) have a cup of coffee in the morning, a glass of wine after lunch and a cigar after dinner.  Than there are others who shun alcohol or any sort of caffeine.

So, what then, was the difference?  Most likely it wasn't the effects of caffeine, or alcohol or an occasional cigar.  It was how they lived their lives.

National Geographic did a very interesting story on the three longest-lived populations on the earth.  If memory serves me correctly, one group was near Italy, one was from the island of Okinawa near Japan and another was a group of Seventh Day Adventists near Loma Linda, CA.

Here was the things they had in common:  they remained active in something that fed them emotionally, they ate naturally, they had strong family and/or friendship groups and they, as a whole, were grateful and optimistic about life in general.

The Italians drank wine with meals (also some breads which I shunned a bit and was evident in their faces and figures - but no one is perfect which is kind of the point of my answer).  But, first thing in the morning the patriarch of the family (who was in his 80's or 90's) went out and chopped wood by hand.  Their meals were 10 or 20 family members sitting down and laughing, enjoying life and the natural food they were eating.

Even more interesting was this: in Okinawa they were starting to see the effects of 'westernization' on their longevity.  For example, the youth in that country were becoming heavier and abandoning their 'old' ways.  McDonald's was becoming more and more common.

My advice: don't stress so much about the effects of caffeine.  I don't.  From what I've read moderate caffeine intake (if you don't have any preexisting medical conditions) is just fine.

Instead, focus on eating natural and base your food choices on color and texture.  Live happy.  Do work you enjoy.  Learn to control what you can.  Stay active in something you enjoy and cherish your family and friends.  And yes, if you want a cup of coffee, have one.  Just don't get carried away.