What's the deal with caffeine?

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  • By Alyssa Dodds, MSBS
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  Caffeine is the most commonly abused drug in the entire world. It is a quick-acting natural stimulant that that stays in the body for about 3-7 hours. It can cause blood pressure to raise and heart rate to increase. The most common source of caffeine is the coffee bean—a natural source—and in a cup of coffee less than 2% of what is being consumed is actually caffeine, the rest of the compound is made up of lipids, carbohydrates, and fats.


              Caffeine is the most commonly abused drug in the entire world. It is a quick-acting natural stimulant that that stays in the body for about 3-7 hours. It can cause blood pressure to raise and heart rate to increase. The most common source of caffeine is the coffee bean—a natural source—and in a cup of coffee less than 2% of what is being consumed is actually caffeine, the rest of the compound is made up of lipids, carbohydrates, and fats.

Caffeine is a drug from a class called methylxanthines that counteracts the body’s natural drive to dilate blood vessels and moderate heart rate; it does this by blocking specific receptors that—when activated—lower blood pressure and heart rate. When these enough of these receptors are blocked, heart rate increases as well as blood pressure. Higher blood pressure levels mean that gas and nutrient exchange that occurs in the microvasculature (capillaries) is somewhat decreased and the exchange is not as efficient. Higher doses of caffeine can cause vasoconstriction—the narrowing of blood vessels and restricting blood flow through capillaries where gas and nutrient exchange occur into the body’s organs and tissues (such as muscle).

              Caffeine ingestion increases the level of epinephrine in the blood which is the hormone that increases blood pressure and heart rate. It also is a factor in the frequent urination that comes with caffeine consumption. So when you drink a lot of coffee or energy drinks and you’re always going to the bathroom, that isn’t because you’re necessarily hydrated, it’s the caffeine forcing your body to get rid of the liquids regardless of how hydrated you are. Because of this, it is really important to make sure you drink more water when you’re consuming caffeine.



              Caffeine is measured in milligrams (mg) and one normal cup of coffee is about 8-10 ounces and contains between 100-150 mg of caffeine. The ideal range of caffeine consumption in a day is 3-5 mg per kilogram (kg) of IDEAL body weight. Ideal body weight varies between men and women, here’s how to calculate it.

              For men:                          2.3 kg x [ height (inches) – 60 ] + 50 kg

              For women:                    2.3 kg x [ height (inches) – 60 ] + 45.5 kg

              For example, a 150 pound woman who was 5 feet 6 inches tall would have an ideal body weight of 64 kg. The acceptable health range of caffeine consumption would be between 191-319 mg caffeine in a 24-hour period. A 180-pound man who is 6 feet tall would have an ideal body weight of 78 kg.  The acceptable health range of caffeine consumption would be between 235-390 mg of caffeine.

              That’s how you calculate a typical range of acceptable healthy caffeine consumption. This method of calculation has been proven to be accurate across various studies UNTIL that upper limit exceeds 400 mg of caffeine in a 24-hour period. Dosages that exceed 400 mg consistently show adverse side effects regardless of ideal body weight and how large the person is in reality (their normal body weight not the ideal body weight calculated). That equates to 3-4 cups of coffee or roughly 2 cans of an energy drink. These adverse side effects include migraine headaches, insomnia, irritability/hostility, nervousness/anxiety, and in very serious cases, heart arrhythmias, seizures, and brain bleeds. Overdose is possible when consuming excessively high amounts of caffeine. In 2018, 92 people died from a caffeine overdose—or caffeine intoxication. These cases were most common in infants, psychiatric patients, and athletes (5 of which were amateur bodybuilders) and the most common method of ingestion was caffeinated medication (pill form) as opposed to consuming energy drinks or coffee.



              Caffeine is also what is referred to as a ‘psychostimulant’ meaning it encourages neural activity and cerebral metabolism in the brain. However, caffeine is very powerful when acting within the brain. Many studies have shown it to significantly reduce cerebral blood flow for extended periods of time. The reduction of blood flow to the brain can cause what is referred to as ‘ischemia’ which means blood-deprivation. This ischemia kills cells by depriving them of oxygen and nutrients necessary to functioning. When ischemia occurs for prolonged periods of time, cells begin to die—and within the brain (and nervous systems) the cells that die are not able to be regenerated. These types of injuries are typically only seen when an individual consumes high amounts of caffeine that exceed the max intake of 400 mg.

              Typically caffeine has desirable outcomes which is why you see people drinking coffee in the morning or an energy drink when they feel tired or not alert. This is due to the nootropic qualities of caffeine which includes the enhanced mental alertness, increase in energy, and ability to focus. While these are common in most of the population, some people experience a less desirable state of alertness—anxiety. This is not the most common side effect but as someone’s intake increases and begins to approach and exceed their recommended maximum intake, anxiety and stress become more prevalent.

              In relation to the brain and its function, caffeine tolerance is a real phenomenon—it begins to take more caffeine to achieve the same ‘feeling’ as you consistently consume it. We have research showing that while the psychological effects—the mental stimulation and alertness—are susceptible to building a tolerance, the reduction in cerebral blood flow is not. As caffeine intake increases, you continue to see further and further reduction in blood flow through the brain which is a dangerous game to play. This tolerance also means that when caffeine is cut-back or cut-out of a daily routine/diet, withdrawals often occur and can continue up to ten days after the last ingestion of caffeine.

              There are other ways however to combat the early morning blues and fatigue. Taking a multivitamin with a complete B vitamin complex is very helpful. These B-vitamins such as niacin are naturally inclined to increase energy levels and wake you up when its early. Staying hydrated when it’s early (or just when you’re tired) can help wake you up. When you’re dehydrated, you’re body has to work harder and use more energy to function which means less of the energy available is going to making your brain wake up. Eating a big breakfast with carbs, fats, and protein is also an effective way to combat sleepiness. This also gives your body ready to use energy to wake up. Caffeine isn’t the only way to get your body ready for the day and there are other healthy options to get you through the day.



              Caffeine intoxication—caffeine overdose—is highly harmful to the heart. As someone’s caffeine intake increases past the safe 400 mg per day the risk of overdose increases. The point at which you begin to seriously be in danger of overdose is when you start consuming more than 2,000 mg (2 grams) of caffeine in a 24-hour period. When someone dies of an overdose the cause of death is due to the severe arrhythmia caused by the caffeine which led to the cardiac arrest (the heart stopping).

              Caffeine affects people differently, the most common affect on the heart is a racing heart rate which can lead to someone feeling shaky or light-headed, as well as heart palpitations. As your caffeine intake increases, the individual may start experiencing more prominent or severe side effects at the expense of the heart.          



              Natural caffeine and synthetic caffeine come from the same source. Caffeine naturally comes from coffee beans, tea, cacao beans, and guarana. Caffeine anhydrous is a common form of caffeine that is often found in sports supplements (such as pre-workout products) and energy drinks. This form of caffeine is derived from coffee beans and is dehydrated and concentrated to make it more potent than naturally occurring coffee beans. Simply put, it allows you to get more caffeine while ingesting a lower amount. Guarana is similar to this. Guarana is a naturally occurring seed that includes caffeine as well as theobromine—another drug from the methylxanthine group that caffeine is in. This seed contains 3-5 times more caffeine than a coffee bean making it more potent than even caffeine anhydrous. The bottom line is that 50 milligrams (mg) of caffeine is always going to be 50 mg of caffeine whether it comes from guarana, caffeine anhydrous, or coffee. What varies among these is the volume of the substance you have to consume meaning you will have to consume a greater volume of coffee than guarana to ingest the same 50 mg of caffeine.



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