Caffeine is a mild stimulant and easily the most commonly consumed nootropic in existence. When consumed by those who lack a tolerance to it, it provides excellent nootropic benefits.
- Reduces mental/physical fatigue, increases alertness/focus 
- Causes faster/clearer flow of thought and better coordination 
- Lowers the risk of certain types of cancer 
- Reduces symptoms of depression and lowers risk of suicide 
What Is Caffeine?
Caffeine is by far the most commonly used and accepted nootropic. Caffeine is an alkaloid that acts as a stimulant on the central nervous system. Unlike many other psychoactive stimulants, caffeine is legal and unregulated virtually everywhere on earth. In North America, close to 90% of adults use this nootropic daily.  Because of caffeine’s popularity, it is the most studied nootropic in the world, yet many people still overlook caffeine’s benefits when constructing their nootropic regimen.
Caffeine Dosage Information
The generally accepted daily dosage for caffeine is 300mg. This translates to approximately 3 cups of coffee. When doses exceed 300mg side effects are much more likely. Consuming amounts greater then 500mg per day can result in a condition defined as “caffeinism” . This condition causes caffeine dependency along with many unwanted side effects including insomnia, headaches, irritability, and nervousness.
How Does Caffeine Work?
Even though chances are you have had a cup of coffee at some point in your life, chances are you don’t understand its inner workings. Caffeine is a water and lipid soluble nootropic that can easily cross the blood-brain barrier.
Caffeine’s main mechanism of action is its action as an antagonist of adenosine receptors. This means it reduces the effects of adenosine. The reduction of the adenosine neurotransmitter is where caffeine derives the majority of its effects. Adenosine is an inhibitory neurotransmitter which plays a role in promoting sleep and suppressing alertness among other functions in the brain. 
However, adenosine is not the only neurotransmitter affected by adenosine receptors. These receptors are also to regulate the release of other neurotransmitters including dopamine and glutamate. 
Safety and Side Effects of Caffeine
Caffeine is regarded as being completely safe when taken at recommended dosages. Consuming large amounts of caffeine can lead to side effects including headaches, anxiety, agitation, and insomnia. Even at lower doses, a mild dependency may occur. The most common withdrawal symptom from caffeine addiction is headaches, though fatigue, difficulty concentrating, and mild depression may occur. Generally, these symptoms pass within a couple of days.
Below are some of the most commonly asked questions about Caffeine. If you have a question that’s not on this list, send it to us at [email protected] and we will answer it for you.
Should I Use Caffeine?
What Are Some Interesting Caffeine Studies?
1. Fuxe K, Ferré S, Genedani S, Franco R, Agnati LF (September 2007). “Adenosine receptor-dopamine receptor interactions in the basal ganglia and their relevance for brain function”. Physiology & Behavior 92 (1-2): 210–7. doi:10.1016/j.physbeh.2007.05.034. PMID 17572452.
2. Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J (1999). “Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans”
3. Haskell CF, Kennedy DO, Milne AL, Wesnes KA, Scholey AB (2008). “The effects of l-theanine, caffeine and their combination on cognition and mood”. Biol Psychol 77 (2): 113–22. doi:10.1016/j.biopsycho.2007.09.008. PMID 18006208.
4. http://www.sciencenews.org/view/generic/id/8965/title/Distracted%3F_Tea_might_help_your_focus ” John J. Foxe of the Nathan S. Kline Institute for Psychiatric Research in Orangeburg, N.Y
5. Lovett, Richard (24 September 2005). “Coffee: The demon drink?”. New Scientist (2518). http://www.newscientist.com/article.ns?id=mg18725181.700. Retrieved 2009-08-03. (subscription required)
9. Iancu I, Olmer A, Strous RD (2007). “Caffeinism: History, clinical features, diagnosis, and treatment”. In Smith BD, Gupta U, Gupta BS. Caffeine and activation theory: effects on health and behavior. CRC Press. pp. 331–344. ISBN 978-0-8493-7102-8.