Effects of Caffeine and Its Side Effects
Many health references tell us to reduce our consumption of caffeine.
Caffeine is not a nutrient or a vitamin or a mineral that the body needs -- such as omega-3, vitamin C, or magnesium. In fact, caffeine has to be detoxified by the liver. Your liver is very busy detoxifying the many chemicals that we are exposed as well as the waste by-products of our metabolism. Putting caffeine into your system just makes it more work for your liver. When the liver gets backed up from overwork, it can not detoxify well and that is when you start to feel the effects of caffeine.
People have different ability to detoxify caffeine. That is why one person can have no effect from caffeine while another can feel the effects right away.
In fact there is a lethal dose of caffeine. The L50 (or median lethal dose) in rats is 192 mg/kg. For humans, you can run the Death by Caffeine calculator. It says that for 150 pound person, it takes 63 cups of brewed coffee. Decaff coffee is not so bad. You need about 1828 cups of decaff to meet the lethal dose.
Coffee and caffeine is not all bad. See this article for some health benefits of coffee.
Caffeine May Hamper Sleep
In the book, The Mood Cure, it lists caffeine and aspartame as two substances that counters the effects of the calming neurotransmitter serotonin. [page 29]
The authors of UltraPrevention has a lot to say about caffeine ...
"Caffeine raises level of adrenaline, causes overexcitation, increases stress, and impairs the relaxation response." [page 241]
"disturbed biological rhythms that include difficulty falling asleep, reduced sleep efficiency, and significant metabolic and mood effects including depression." [page 312]
Caffeine May Increase Blood Sugar
Caffeine increase the stress hormones and adrenaline which causes a rise in blood sugar.
Caffeine May Be Protective Against Alzheimer's Disease
On the positive side, there are some studies that shows that caffeine may be protective against Alzheimer's disease.
The Journal of Alzheimer's Disease mentions of a mice study where transgenic mice with Alzheimer disease that were given caffeine showed some protection from the development of certain cognitive impairment and improved working memory. They also have decrease of amyloid beta in the hippocampus of the brain. The amount of given caffeine is in the human equivalent of 5 cups of coffee a day.
In National Public Radio program titled "Nervous About Alzheimer's? Coffee May Help", it mentions that neuro-scientist Gary Arendash is convinced from mice studies that coffee helps prevent Alzheimer's. He drinks 5 to 6 cups a day. This is a lot of coffee, more coffee than many people can take. Some people being more sensitive to the side effects caffeine than others. However, there are many other better ways of reducing the risk of Alzheimer's.