Phil Maffetone on Caffeine

Caffeine is a common source of adrenal stimulation, a main reason people consume it. Coffee, tea and colas are the main sources. If you have an adrenal problem, assess your caffeine intake. For many, no caffeine is best; for others, a single cup or two of coffee or tea may be tolerable. You must determine, as objectively as possible by listening to your body, how much caffeine you can tolerate. http://www.philmaffetone.com/stress.cfm

the very small amount of caffeine in green tea is not likely to have adverse affects in a relatively healthy athlete. It also have many positive phytonutrients to help the immune system and muscles.  http://www.philmaffetone.com/forum.cfm?forum_action=showposts&topicid=94182

caffeine can be harmful for some people at certain doses. Because it stimulates the adrenal and nervous systems, those who already have too much stimulation - via natural means or through lifestyle stress - can easily be harmed by too much additional caffeine. eighteen ounces of coffee is more than 'a single cup' -- it could be considered three cups! So, depending on the strength of the brew, it's a lot of caffeine.
Only you can determine whether you do better with less caffeine through experimentation. Some people benefit by cutting their caffeine down a bit. For example, you may feel just as good with half the amount of caffeine. If that's the case, drink half the coffee or mix in half decaf. Other people develop symptoms such as hunger, shaking, and over stimulation of the intestines (often causing diarrhea) which would indicate too much caffeine, even in very small amounts.
Another important factor is that you're not eating breaking, and instead, relying on caffeine to keep you going. The body uses much of its stored glycogen during sleep, and replacing this stored sugar from breakfast is very important. Many people don't feel right working out after a meal of solid food. But a smoothie, even a small one, is usually tolerated very well, even when accompanying caffeine. http://philmaffetone.com/forum.cfm?forum_action=showposts&topicid=88708

Carbohydrate Intolerance Health Survey—Some Common Signs and Symptoms 
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11. Frequent cravings for sweets or caffeine
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caffeine stimulates the sympathetic nervous system, which raises the heart rate slightly in most people. Too much stimulation can raise the HR too much, an indication that the caffeine is too stressful and should be avoided.
In addition to stimulating fat burning, caffeine also gives the user the impression of less discomfort, one key reason people consume it before racing.
Shorter races work best--up to 60-90 minutes. Beyond that time frame, the effects of caffeine quickly diminish.
If you don't normally drink caffeine, having it only on race day can produce unwanted side effects. These include being anxious and jittery (perhaps making pre-race jitters worse), and having to run to the toilet before and or during the race.
Like many other issues, the use of caffeine is individual--carefully and objectively experiment in races. http://www.philmaffetone.com/forum.cfm?forum_action=showposts&topicid=105402