Plants such as coffee, tea and cacao contain caffeine. Caffeine stimulates the central nervous system promoting wakefulness by competing for adenosine receptors. Adenosine is produced by the body to promote sleep and constrict blood vessels to allow more oxygen into the brain during sleep. Caffeine is a molecule that is similar in shape to the adenosine molecule. The nerve cells are unable to tell the difference between caffeine and adenosine allowing caffeine to block adenosine. This is the primary mechanism of caffeine to promote alertness, minimize migraine headaches, stimulate muscles and produce pleasure.
The most notable beverages that contain caffeine are coffee, tea, energy drinks and sodas. The amount of caffeine in these beverages ranges from 30 to 400 mg per serving. Migraine medicines like Excedrin and Anacin contain caffeine with other pain relievers to treat migraine headaches. Many over-the-counter and prescription medications such as migraine medications, diuretics, appetite suppressants, alert inducers and cold medications contain caffeine. Caffeine is also naturally occurring in Guarana, Cocoa (chocolate), and Yerba Mate. Caffeine is frequently added to soda beverages and is another source of caffeine; however, soda is not recommended due to the high sugar content that can cause spikes in blood sugar, which may worsen symptoms of headaches.
Mechanism of Action
Caffeine is a molecule that blocks receptors of adenosine, a nervous system chemical that causes physiological effects to take place. Adenosine is responsible for the sleep-wake cycle, so caffeine works by displacing adenosine and causing alertness. Caffeine can also block calcium channels in the muscles allowing for increased strength and endurance of the muscles. Adenosine is responsible for the dilation of blood vessels in the brain. Caffeine competes with adenosine at the receptor site causing the blood vessels to then constrict, alleviating migraines and headaches.
Adenosine begins to accumulate in the brain and when levels reach high enough, you will begin to be sleepy. Caffeine blocks adenosine from causing sleepiness and increases the rate of neurons firing in the brain. This increase in adrenaline causes the body to believe it needs to fight or run. Dopamine is triggered by caffeine and causes the brain's pleasure centers to become active. This secondary effect of caffeine may also decrease the negative effects of migraines by increasing pleasure in the brain.
Side Effects and Tolerance
Caffeine can produce many positive effects like helping to alleviate migraines and increasing energy levels. Like anything else, caffeine should be consumed in moderation. Side effects of caffeine consumption include thirst, anxiety, insomnia, irritability, blurry vision, dry mouth, clamminess, sweat production, increased blood sugar and urination, respiratory distress, rapid heartbeats and diarrhea.
Caffeine is the most widely used drug in the world that acts in a psychoactive manner. It is a widely available, legal substance for people of all ages to enjoy. Tolerance occurs quite rapidly as more caffeine is consumed. More adenosine receptors are created to compensate for increased caffeine consumption. This leads to hypersensitivity to adenosine when caffeine is not consumed contributing the negative side effects associated with decreased caffeine consumption. Migraine medicines contain substantial amounts of caffeine. If the consumption of caffeine-containing substances including migraine medications suddenly cease, adenosine will then act on receptors. Adenosine will cause blood vessels to dilate increasing blood flow to the brain contributing to headaches and migraines.