Caffeine
Caffeine is a bitter, white crystalline alkaloid that occurs naturally in coffee beans, tea, kola nuts, cocoa plants, yerba mate and guarana. The caffeine in the stems, roots and leaves of these plants acts as a natural pesticide, causing paralysis in insects that try to eat the plant. Although people in many countries have used these plants for their stimulating properties for many years, it wasn't until 1819 that a German chemist discovered that the substance caffeine was responsible.
Caffeine also affects the nervous system of humans, although not in such a deadly way. Caffeine is an antagonist to the adenosine receptors in our nervous system, meaning it turns the receptors off. Adenosine is a neurotransmitter with an inhibitory effect on central nervous system, so turning off the receptors for this substance causes the nervous system to be stimulated. People who consume caffeine regularly will increase the amount of adenosine receptors in their central nervous system. This way they can still utilize the adenosine, and the stimulatory effects of caffeine are reduced.
When a person stops drinking large amounts of coffee, they are suddenly increasing the physiological effects of adenosine, since they have all those extra receptors. Adenosine is a vasodilator, so person on coffee withdrawal has an increased flow of blood to head, causing headache and nausea. Other symptoms are fatigue, anxiety, irritability, inability to motivate, and mild depression. Over the course of several days or several weeks your body will revert back to the normal adenosine receptors and these symptoms will go away.
The half life of caffeine in normal person is anywhere from 4-7 hours, meaning that is how long it hangs around affecting your systems. Adenosine is the neurotransmitter that promotes sleep, so this is how long it can keep you awake if you haven't built up a resistance. Even after you do get to sleep, caffeine can prevent slow-wave or deep sleep, and fragment your sleep so you wake up frequently during the night.
Caffeine is to blame for most of the adverse effects that people experience from drinking too much coffee. Some of these are tachycardia, palpitations, insomnia, restlessness, nervousness, tremor, headache, abdominal pain, nausea, vomiting, diarrhea, and diuresis (increased urination). Caffeine increases production of stomach acid, which can lead to ulcers and esophageal disease and GERD.
Caffeine can also be beneficial. A study in International Journal of Sports Nutrition and Exercise Metabolism, April 2009 found that caffeine may limit muscle pain after a workout by blocking adenosine. Adenosine is normally released as part of the inflammatory response to injury and can activate pain receptors in body cells.
Caffeine makes your body absorb pain medications more quickly and makes them 40% more effective at relieving headache. Read about some of the studies that have been done. Caffeine has been found to decrease the elimination of acetaminophen from the system, and to increase the bioavailability of aspirin. Many pain-relievers on the market today combine caffeine with aspirin and/or acetaminophen, especially when they are marketed for headaches or migraines.
There are also many drugs that can alter the way your body metabolizes caffeine, so that the effect of the caffeine is increased. Examples are cimetidine (Tagamet), disulfiram (Antabuse), estrogens, fluconazole (Diflucan), fluvoxamine (Luvox), mexiletine (Mexitil), quinolone class antibiotics, and terbinafine (Lamisil).
Coffee is being studied for its role in preventing several diseases such as Parkinsons, liver disease, colorectal cancer, and Type 2 diabetes. However it isn't clear whether it is the caffeine that is protective or some other substance in the coffee. In fact, in some studies decaffinated coffee had the same effects on a health condition as regular coffee.
Caffeine increases the secretion of cortisol in both men and women, especially when they it is consumed when the person is under stress, or just before exercise. Cortisol comes from the adrenal gland, and prolonged high levels can have negative effects like suppressed thyroid function, decreased bone density, blood sugar imbalance, lowered immune response and increased abdominal fat. Let me say it again - caffeine causes your body to secrete a hormone that increases abdominal fat! Anyone who is struggling with their weight should seriously take a look at the amount of caffeine they consume.
So caffeine has some beneficial effects, such as helping pain medications to work, decreasing muscle pain with exercise, and it may play a role in prevention of several diseases. On the other hand, it can interfere with sleep, stimulate production of stress hormones, cause a whole list of unpleasant symptoms, and cause an increase in abdominal fat! Studies have shown that decaffeinated coffee has the same preventive effect against certain diseases as coffee with caffeine. Caffeine is an addictive substance that causes unpleasant withdrawal symptoms. If you consume a lot of caffeine, be aware of the effects it is having on your body, and decide whether you think they are worth it.
The information on this page is not meant to be used in treatment of medical conditions. Please seek the advice of a physician about any medical condition or symptom. Those with medical conditions should consult a medical professional about the appropriateness of taking dietary supplements or diet therapy, and how these methods will interact with their medications.
Phytochemical Society of North America
Phytochemical Society of Europe
For detailed information about the chemical structure, formula, and molecular weight of various phytonutrients, visit
The US Dept of Agriculture.
Phytochemicals also gives detailed information on specific phytochemicals.
Search for herbs at the Sloan Kettering Memorial Cancer Center website.