The Effect of Caffeine on Human Blood Pressure
Created by Bryanne N
6th grade SOAR
The purpose of this experiment was to determine if caffeine affects the blood pressure of 6th grade girls.
I became interested in this idea from watching the news and word of mouth. I had heard that caffeine affected many bodily functions but I didn’t know if it affected blood pressure or how. I also know that having high blood pressure is a heath problem.
The information gained from this experiment could be used to warn people not to drink too much caffeinated pop, as it may raise the blood pressure.
My hypothesis is that when caffeine is consumed in large amounts it will increase the blood pressure.
I base my hypothesis on my research that said caffeine affects many bodily functions and it also increases heart disease.
The constants in this study were:
The amount of Diet Pepsi each girl drinks,
How much time I wait between trials,
What the girls do while waiting to have their blood pressure taken,
The person taking the blood pressure,
Using the same blood pressure cuff and gauge for each girl.
The manipulated variable was the amount of caffeine the girls drank. The first time I took their blood pressure they had no pop in their system. The second time I took their blood pressure they had had one can of Diet Pepsi. The third time I took their blood pressure they had had two cans of Diet Pepsi.
The responding variable was the blood pressure, both systolic and diastolic.
To measure the responding variable a registered nurse used a blood pressure cuff 50 minutes after the subject drank the Diet Pepsi.
QUANTITY ITEM DESCRIPTION
Sphygmomanometer, an instrument that measures blood pressure, using an inflatable blood pressure cuff and gauge.
Girls from the Selah Middle School SOAR Program
Cans of Diet Pepsi
1. Make sure all the materials are available and that every girl has her permission slip in, and is present. Each should have eaten some breakfast. None of them can have consumed any tea, pop, coffee, or other caffeinated substances.
- At eight forty-five, in the morning, take each of the girls’ blood pressure, record the order.
- Record each blood pressure of each girl as B.P.0.
- Right after the blood pressure is taken, have each, girl, drink a full can, 355 ml. (12 fluid ounces,) of Diet Pepsi within 5 minutes.
- Wait 45-55 min from when each girl finishes the Diet Pepsi, and then take her blood pressure again, using the same order. Record the numbers as B.P.1.
- Immediately have each drink another 355ml. can of Diet Pepsi.
- Again wait another 45-55 min. until testing the blood pressure, in the same order.
- Record their blood pressure as B.P.2.
- Calculate each girl’s blood pressure change. The change is the difference between the blood pressure with no caffeine and with 1 can of Diet Pepsi, and the difference between no caffeine and two cans of Diet Pepsi.
My project is the Effect of Caffeine on Blood Pressure. At the beginning of this project I knew only that caffeine affects a lot of things, but not exactly what. Through reading I found out what it affects and a lot more. Below you will read almost everything that I found out.
Caffeine is a bitter white crystalline alkaloid. Its chemical formula is CaH10N4O2. Caffeine is a drug that affects the human body.
What Does it Raise?
It raises the heart, respiration, and basal metabolic rate. These things are all called a "lift." But these things differ from person to person. It matters if a person reaction time is different, and how much is taken in.
What, Where, When, How, The Side Effects Start?
The side affects can start as early as 15-45 min. after entering the body. It will always have an affect as long as it is in the blood. Caffeine affects the central nervous system; it can affect anywhere because it is carried in the blood. A common symptom, like a headache, can start about 18-24 hours after the last dose of caffeine. A few other symptoms are drowsiness, yawning, nervousness, depression, etc.
Oh No! An Overdose!
Once again the sensitivity and effect varies from person to person. An overdose of 2-7 cups can cause restlessness, nausea, headaches, tense muscles, sleep disturbances and irregular heart beat. An overdose of 7 cups or more can cause ringing ears, light flashes, etc.
Are Pregnant Women in Danger if They Drink Caffeine?
Yes, pregnant women can contribute to their baby’s birth defect if they have too much caffeine. It has been known that caffeine can pass through the placenta and also pass into the mother’s milk. In 1980 the FDA advised pregnant women to reduce the amount of caffeine that they drink. A birth defect can happen if 56-87 cups of caffeine are taken in all at once. But if 4-28 cups are drank it should cause no birth defect.
Can You Decrease the Effects?
A few things that can decrease caffeine’s negative affects are to dilute coffee or tea with milk, watch for effects and once you see one stop. If caffeine causes you problems, please consider gradually changing to decaffeinated coffee, tea, pop or another kind of beverage.
If caffeine is consumed 30-60 minutes before going to bed, it can cause restlessness and trouble getting to sleep. Also, a tendency to be awakened more easily by sudden noises can occur.
Caffeine or other ingredients may increase heartburn, ulcers, heart problems, and Fibrocystic Breast Disease.
"Researchers at Johns Hopkins Medical Institution recently found heavy coffee drinkers (about 5 cups of more) are two to three times more likely to have, or get, a heart disease than nondrinkers."
The Blood Pressure Cuff
To measure the blood pressure you must use the blood cuff, which is attached to a pressure gauge. You would need to listen for two things, the systole and the diastole. The systole is the top number and is the first beat that you will hear. It is also when the ventricle contracts forcing the blood through the arteries. The diastole is the bottom number and is the last beat that you hear. It is also when the ventricle relaxes and fills up with blood. The pressure is given in millimeters of mercury. The following statement shows how to read a blood pressure reading.
BP = Systolic/Diastolic = 110/80 = ventricle contracting/resting beat
Caffeine raises a lot of bodily functions but the things that it raises differ from person to person. These things are called a "lift."
The side effects can start as early as 15-45 min. after entering the body. It will always have an effect as long as it is in the blood. You can only get a minor affect with 2-7 cups. A bigger effect can happen when you drink 7 or more cups of caffeine.
Pregnant women can only have a birth defect if she drinks 56-87 cups all at once. So if she drinks 4-28 cups she will not have an effect.
There are ways to decrease effects; one way is to, dilute coffee or tea with milk.
Caffeine can increase your chances of getting heartburn, having heart problems, etc.
If caffeine is consumed 30-60 minutes before going to sleep, it can cause restlessness and trouble getting to sleep.
The original purpose of this experiment was to determine if caffeine effects the blood pressure of 6th grade girls.
The results of the experiment varied from person to person. The data showed no clear pattern That’s true because of the person. Their weight, height and other different things, play a part in the result. When I calculated the change between blood pressure 0 and blood pressure 1, in systolic, five of the girls’ blood pressure went up a lot, five went down a lot and a few stayed the same. For the same change but, in diastolic five went up a lot, three went down a lot and five stayed the same a little. When I summed out the change between blood pressure 1 and blood pressure 2, in systolic, about four went up, three went down and a few went nowhere or stayed the same. For the same change, but, in diastolic three went up a lot, two went down a lot and eight stayed the same or went down a little or up a little.
My hypothesis was that when caffeine is consumed in large amounts it would increase the blood pressure.
I base my hypothesis on my research that said caffeine effects many bodily functions and it also increases heart disease.
The results indicate that this hypothesis should be rejected. It is difficult to make my conclusion because the results vary so much from girl to girl. It is true that some subjects showed an increase but too many did not.
Because of the results of this experiment, I wonder if there will ever be an experiment done that will give a more accurate answer. That experiment, though, will take a lot of time.
If I were to conduct this project again to get a more accurate answer, I would give the girls a longer time to drink the Diet Pepsi. The amount of caffeine that they got to drink was not nearly enough to give me a pattern. I would also need a bigger sample size. With that I would also need to control their weight.
Bayer, Barbara "Caffeine" World Book Encyclopedia, 1994, Vol. 3, pg. 14.
Seachrist, Lisa "Coffee May Not Be So Bad " Newsweek, Nov. 25, 1995, Vol. 126, issue 20, pg. 87
Gilbert, Richard "The Encyclopedia of Psychoactive Drugs Caffeine, the Most Popular Stimulant", New York, Chelsea House Publishers, 1986, pg. 73-110