Cutting down on caffeine makes sense for a number of reasons, but perhaps the most important is that caffeine is medically classified as a poison. Around 10 grams of caffeine (70 - 100 cups of coffee) can be fatal (if taken at one time.)

Adverse effects can include the inability to fall asleep, interrupted wakeful sleep, mood changes (anxiety, depression and irritability), heartburn, stomach upset, increased headaches and irregular heartbeats. Caffeine - sensitive individuals or occasional caffeine consumers find these effects to be more dramatic. Heavy coffee drinkers often become desensitized to some of the effects but they also become dependent on its stimulant effects. For them, caffeine reduction often brings headaches and withdrawal symptoms.

Excessive caffeine is not recommended for women trying to get pregnant, for pregnant and breast-feeding women or individuals with an ulcer. Some women with fibrocystic breast disease have reduced symptoms of pain and tenderness after avoiding caffeine. Moderation or abstinence for these individuals is the prudent choice.

Cardiac disturbances, which include irregular heartbeats and temporarily increased blood pressure, have been documented with caffeine consumption. Whether caffeine can actually cause heart disease and/or heart attacks is a hotly debated issue with no conclusive evidence.

Caffeine has been found to decrease the body’s absorption of iron and to some extent calcium. For best absorption of these nutrients, caffeine should not be consumed with high iron and calcium food sources.

---National Institute of Health

Caffeine’s Role in Headache Treatment

It (caffeine) can relieve certain types of headaches (vascular headache ie: migraines) by constricting blood vessels in the brain…

---National Institute of Health

TENSION headaches involve the tightening or tensing of facial neck muscles. Caffeine doesn’t have much of a role here. In fact, caffeine can even exacerbate a headache problem.