How does caffeine work as a stimulant? Caffeine is a naturally occurring substance found in plants and food substances—both organic and processed. It’s also a stimulant that works by blocking adenosine inside your cells. In this video I show you how this works. The following questions are answered in this video (go straight to the time stamp): How does caffeine work in the brain? (0:33) How does caffeine help headaches? (1:31) How does caffeine hurt your sleep? (1:56) What is heavy caffeine consumption? (2:25) What is the caffeine content in certain foods? (3:08) What are the negative effects of caffeine? (5:30) When should you drink your last cup of coffee? (7:06) Here's a more detailed explanation. Adenosine is produced in the cells of the brain and other organs. And it’s a chemical involved in inducing or bringing on sleep by slowing the activity of the cell. Caffeine is similar in structure to the adenosine molecule so when you drink coffee and digest it, the caffeine in the coffee travels to you brain and binds to the cells and blocks the adenosine from binding. Without the adenosine to slow things down, your adrenal glands get the signal to release the flight or fight hormone, epinephrine. Epinephrine –also known as adrenaline then acts to increase alertness, increase your heart rate and constrict blood vessels. So this is the high you get from caffeine – from the boost of adrenaline. Also as an aside, the constriction of blood vessels that follow caffeine consumption is the basis for caffeine being a part of headache medicines. It constricts the blood vessels in the brain (through the epinephrine release), which gives the tissues more space and relieves some of the tension producing the headache. Caffeine affects your sleep in a couple of different ways. First, it extends your sleep latency, which is the period of time it takes to fall asleep. It also shortens the total amount that you sleep. The older you are, the more sensitive you are to these effects. Similar to alcohol, caffeine has a diuretic effect, which causes the body to lose water. How much caffeine does it take to affect your sleep? Depending on the amount of time between consumption and going to sleep – I would say anything from 200mg of caffeine or more can create that delayed sleep effect. A moderate doses of caffeine would be anything between 200 and 300mg per day. Heavy caffeine consumption would be considered anything from 500mg per day or more. Well what does that mean exactly? Here is an example: 6:40 Imported coffees and teas can also carry higher caffeine concentration. And also, the brewing method used will also affect the caffeine content. Once you consume the caffeine, it is digested through the stomach and small intestine and enters the bloodstream within thirty minutes to an hour. This relatively rapid response time is one of the reasons a cup of coffee is so popular as a morning crutch. So what about the half life? The half-life is the amount of time it takes for something to decrease to half its original quantity. The half-life of caffeine varies among different studies, but it is generally believed to be between 3 1/2 to 6 hours. It can take longer in some people with certain medical disorders or under the influence of certain medications. For example, birth control pills can inhibit or slow the half life of caffeine, making it so that it takes five to ten hours for the amount of caffeine in the bloodstream to decrease by half. Pregnancy and liver disease also significantly extend the half-life of caffeine. Here is a practical example: Suppose you were to drink a tall Starbucks coffee at 9:00am. That size has 230mg of caffeine. If we assume the caffeine carried a half-life of five hours, you would have approximately 130mg of caffeine in your system at 2:00pm that afternoon from that single cup alone. Now this is an approximation, but because of the variability in how we metabolize caffeine, some experts recommend not consuming any caffeine after noon. I’m in that camp. I usually recommend to people that your last drink of coffee happen before noon. Stay tuned for the next video mentioned in the video – the affects of aging on sleep. Visit my channel for more videos: null Subscribe to get notified about my latest videos: https://goo.gl/DFfT33