By Kristin Sheppard
How much caffeine do you drink daily? I know that my daily intake is relatively high compared to some of my friends, but low compared to others. In the morning I make myself 12 ounces of coffee and mix it with 2 packets of hot chocolate mix to help me wake up (it’s my own cheap version of a mocha!). By midday I’m feeling tired again so I either get a latte from the library patisserie or a bottle of soda. And at night I have another soda to help me focus on my homework. According to the “Caffeine Content in Common Drinks and Foods” chart created by the University of Washington, I’m drinking about 320mg of caffeine daily, not counting any chocolate I may eat. It turns out, this amount of daily caffeine intake is fairly normal, and considered to be safe by the Food and Drug Administration (the FDA). The FDA reports that many doctors consider a moderate amount of caffeine consumed daily to be safe, but what is a moderate amount of caffeine? According to the doctors that the FDA consulted, it’s about 200mg of caffeine daily (oops, I guess I’m a little over) and a dangerous level is about 600mg of caffeine daily.
|Caffeine Content in Common Drinks and Foods|
But what does caffeine do to your body? It has been found in mice that caffeine binds to certain receptors in neurons and heart tissue. Remember that neurons are cells that are involved in your nervous system and the receptors are part of what allows cells to communicate with each other. One of these receptors is A1-adenosine receptor. A1-adenosine receptors are known to be located in many different parts of your body, including your brain and your heart. When this receptor is stimulated it is known to stop the release of excitatory neurotransmitters in the brain, meaning that it is less likely that the neuron with the A1-adenosine receptor will communicate with the next neuron. However, when caffeine binds it stops the activity of these A1-adenosine receptors. This means that when caffeine is present, more excitatory signals will be fired between neurons. Binding of caffeine to these receptors in the heart also leads to a change the strength, rate and conductivity of the heartbeat.
There have been a number of studies on caffeine and how it affects hypertension (high blood pressure) in adults and adolescents, arrhythmias (problems with the rate or rhythm of your heart beat), and several other cardiovascular diseases. In every study and review that I have read, it shows that administering 200-300mg of caffeine in pretty much any form has no long-term affect on any individual of any age group (excluding very young children and infants, there have not been many reports on this age group). The closest thing to a dangerous result was reported in a study done in 2011 by Arthur Euman Mesas et al; they found that administering 200-300mg of caffeine to adults who already have hypertension, but do not regularly drink caffeine, have a sudden, short-term increase in blood pressure lasting approximately 3 hours. However, similar results were not found for individuals who had hypertension and drank coffee daily for 2 weeks, nor did they find any link between long-term coffee consumption and heart disease.
|Moderate amounts of coffee have been shown to be safe for daily consumption|
Although these studies are useful for telling me that I’m not going to have a heart attack from drinking my daily coffee and soda, they do have their limitations. Every study I have read relies on self-report of how much caffeine an individual drinks or the people they study are only administered a moderate dose of caffeine. However, people can only be administered what is thought to be a safe dose of the drug by scientists who are studying the effects. It is unethical to knowingly deliver something that may be dangerous to the individuals participating in the study. This means that in humans a direct cause-and-effect for too much caffeine cannot be studied. We must rely on those reports from individuals who have claimed to have adverse reactions to high doses of caffeine to try and find a relationship between caffeine and these undesirable symptoms.
So what happens when you start getting to those dangerous doses? Just like any other drug, you can overdose. Symptoms of caffeine overdose in adults can include trouble breathing, irregular heart beat, rapid heart beat, muscle twitching, hallucinations, changes in alertness, confusion, sleeping trouble, convulsions, diarrhea, dizziness, fever, increased thirst, increased urination, or vomiting.
Although these symptoms can be frightening, it is easy to think that it would be fairly difficult to consume that much coffee or soda in one day, and this may be true. But the fairly recent introduction of energy drinks and caffeine pills increases the risk of overdose. One of the more popular energy drinks that I see people drinking is “Monster Energy.” Did you know one 24-ounce can of “Monster Energy” contains 240mg of caffeine? That means that after one can of this stuff you should be done with caffeine for the day. So what about if you drink two or three cans? According to the FDA there have been 40 alleged adverse event reports since 2004 related to "Monster Energy" products alone. These reports include everything from non-serious illnesses to life threatening hospitalizations, and even five cases of death. Those numbers pale in comparison to the 92 reports (including 12 deaths) allegedly related to the also popular “5 Hour Energy” that have been filed with the FDA since 2005.
|Popular energy drinks available at most grocery and convenience stores|
So what can we take away from all of this? I think that the best thing to remember is that even though caffeinated beverages may be delicious and deliver that extra boost you need to get through the day, try to keep it in moderation. Although a moderate amount may be appetizing and pleasurable, too much can be dangerous.
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Green, R.M., and G.L. Stiles. 1985. Chronic Caffeine Ingestion Sensitizes the A1 Adenosine Receptor-Adenylate Cyclase System in Rat Cerebral Cortex. The Journal of Clinical Investigation. 77:222-227.
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Shi D., O. Nikodijevic, K.A. Jacobson, and J.W. Daly. 1994. Effects of Chronic Caffeine on Adenosine, Dopamine and Acetylcholine Systems in Mice. Archives Internationales de Pharmacodynamie et de Therapie. 328(3):261-287.
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2012. CFSAN Adverse Event Reporting System, Voluntary and Mandatory Reports on 5-Hour Energy, Monster Energy, and Rockstar. U.S. Department of Health and Human Services, Food and Drug Administration. <http://www.fda.gov/downloads/AboutFDA/CentersOffices/OfficeofFoods/CFSAN/CFSANFOIAElectronicReadingRoom/UCM328270.pdf>