Caffeine is a central nervous system stimulant contained in a number of popular beverages, including coffee, tea and a wide variety of soft drinks. Acetylcholine is a chemical in your brain and body that helps transfer signals inside your nervous system. Caffeine can make certain changes in your brain function by boosting acetylcholine’s effects.
Caffeine belongs to a class of chemicals called xanthines. It achieves its stimulating effects by countering the activity of a natural xanthine called adenosine, which normally helps you sleep when it builds up in your brain. Other effects of the chemical include increases in your heart rate, relaxation of your airways and narrowing, or constriction, of your blood vessels. When you consume caffeine, its effects start to take hold in as little as 15 minutes. It takes more than half a day for caffeine to completely leave your system.
Like adenosine, acetylcholine belongs to a class of substances called neurotransmitters. Neurotransmitters send messages through your nervous system by passing between nerve cells and binding to specialized proteins called receptors. This binding activates the receptors, which open and allow charged particles called ions to flow into the cells’ interiors. Acetylcholine and its specialized receptors are located in your brain and the rest of your central nervous system, as well as in muscles throughout your body. Acetylcholine molecules are relatively small when compared to most other neurotransmitters, and have the ability to send messages between your nerve cells at a very rapid rate.
When you sleep, a natural sedative in your brain triggers a significant decrease in the acetylcholine levels in your central nervous system, the National Institute of Mental Health explains. Apparently, this drop in acetylcholine allows your brain to form the chemical associations that give you the ability to remember the individual words in your vocabulary. According to a 2008 study published in “Behavioral Brain Research,” when you drink caffeine, it can block the activity of the sedative that lowers your acetylcholine levels and trigger a subsequent abnormal increase in your central nervous system’s acetylcholine supply.
Increased acetylcholine levels in your memory centers can diminish word/memory associations by blocking your brain’s ability to replay newly acquired information, the authors of the study in “Behavioral Brain Research” report. In addition, caffeine’s effects grow worse as your need to associate memories with specific words increases. The authors of the study note that their findings run counter to common assumptions about caffeine’s ability to improve your performance of mental tasks. In many cases, you could potentially gain a greater performance improvement by taking a daytime nap. Consult your doctor for more information on the interactions between caffeine and acetylcholine.
- University of Washington: Caffeine
- World of Molecules: Acetylcholine
- "Behavioral Brain Research": Comparing the Benefits of Caffeine, Naps and Placebo on Verbal, Motor and Perceptual Memory; Mednick, Cai, et al.; May 8, 2008
- "Annals of Medicine": Adenosine in Sleep and Wakefulness; T. Porka-Heiskanen; April 1999
- Protein Data Bank: Acetylcholine Receptor; David Goodsell; November 2005