EFFECTS OF CAFFEINE ON HEART RATE

EFFECTS OF CAFFEINE ON HEART RATE

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EFFECTS OF CAFFEINE ON HEART RATE

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EFFECTS OF CAFFEINE ON HEART RATE

Stephanie ThompsonGeorgia State University

Problem

The purpose of this study is to find out the effects of caffeine on an individual’s heart rate. The reason this study was completed was to see if different levels of caffeine affect the heart rate differently. This study was also completed to be able to educate students in life science classrooms when they are studying the body systems, specifically the circulatory system, on the effects of different factors to help them link healthy habits to life science.

Background Information

The heart rate, or the pulse, is known as the number of times your heart beats per minute (“All About Heart Rate,” 2014).  An individual’s resting heart rate is the point where the heart pumps the lowest amount of blood needed for your body to function because there is no activity going on. Most adults have a resting heart rate between 60 to 100 beats per minute (bpm).  An individual can check his/her heart rate at any of the following locations: the wrists, inside of the elbow, side of the neck, at the top of the foot, as well as on the chest near their heart (“All About Heart Rate,” 2014).  There are various factors that can affect an individual’s resting heart rate such as activity level, body size, mood, and medication.  People who are very active will have a lower resting heart rate because their hearts do not have to work as hard to complete daily activities.  This is a result the conditioning gained through activity. It is important to note this only occurs when the individual participates in vigorous activity several times a week over a number of years. An individual who is considered obese, not just overweight, can have a higher resting heart rate due to the fact that the heart has to work harder to circulate blood throughout the body. Only those who have a body mass index over 30 would be considered obese.  It is noted even with the increase, their heart rates still should not be over 100bpm. A person’s mood can raise the heart rate as well.  If an individual is extremely happy, sad, stressed, or anxious, a rise in the resting heart rate may be present.  Some individuals take medications to increase their heart rate, but sometimes medications people take may include increased heart rate as a side effect. Anti-depressants, amphetamines, norepinephrine bitrates, bronchodilators, and illicit drugs such as cocaine and ecstasy are known to increase heart rates.

Caffeine is an alkaloid found in various plants such as coffee beans, tea leaves and cocoa beans and “it is one of the most ingested pharmacologically active substances in the world” (Narwot, 2002).  Caffeine can be found in multiple sources at varying doses. Some of the sources of caffeine include candies, chocolate, energy drinks, coffee, tea, pain relievers, and cold medicine.  Caffeine has been found to enter almost every part of the body including placenta, breast milk, semen, and across the blood-brain barrier. It is recommended that an individual who is consuming caffeine should only intake less than 400 milligrams of caffeine a day. After being ingested, caffeine is absorbed through the gastrointestinal tract and carried in your bloodstream throughout the body and the effects from caffeine can be seen as quickly as 15 minutes after ingestion.   It is metabolized primarily in the liver and remains in the body anywhere from 3 to 7 hours. Caffeine's effects on your heart rate occur indirectly, as a result of its effect on your nervous system (K. Meininger, 2014). Studies have been conducted to find the effects of caffeine on heart rate. Many studies have stated that caffeine is a stimulant and can cause an increase in heart rate at higher does. In one study completed by James and Green they found that a change of heart rate can be seen when the dosage of caffeine is higher than 150mg. The study showed the subjects’ heart rates decreased. They also noted that a tolerance can be formed through continual usage of caffeine at these high levels.  Once an individual forms a tolerance, the change can no longer be observed or it can be so small causing it to be irrelevant. Astrup, Toubro, and Cannon completed at study on thermogenic, metabolic, and cardiovascular effects in healthy volunteers and found that caffeine can have multiple effects on heart rate.  In a double blind study participants were given either a placebo, or one of 3 caffeine doses (100, 200, and 400mg) and they found after 15 minutes that the heart rate in participants that received caffeine would initially reduce.  They took a second measurement after an hour had passed and they found that the heart rate had now raised above the participant’s resting heart rate.  The amount of the increase was directly correlated to the amount of caffeine the participant consumed.  The researchers did find that participants who were given the 400mg dose experienced some side effects such as heart palpations, dizziness, headaches, and anxiety.  

Hypothesis

Based on the background information that was collected, if more than 60 milligrams of caffeine is consumed in a caffeine-based product, an individual’s heart rate will increase fifteen minutes after it has been ingested.

Experimental Design: Procedures and Materials

The independent variable in this research was the caffeine-based products and the dependent variable was the heart rate changing based on the product consumed.

The materials needed for the experiment included:

· Jet Alert caffeine pills

· Room temperature water (to help consume pill)

· NOZ energy drinks

· Starbucks Double-Shot Espresso coffee drink

· 6 volunteers

· Notepads and pens/pencils

· Pulse rate measuring device

· Timer

· Health survey

The volunteers that participated in the study were requested to fill out a health survey prior to completing the study to assure there were no underlying issues such as irregular heart beat that would create incorrect results. The survey included questions regarding their age, height, weight, current daily caffeine intake, stress level, activity level, and drug usage (prescription/non-prescription).Based on the survey the participants took, I decided to choose the three caffeine-based products to ensure if the participants had built a tolerance, the results would not be affected by choosing products with low levels of caffeine. During the process of the experiment, each subject had their resting heart rate taken three times while sitting down. After the heart rate is taken, they were given the caffeine-based product to consume; the individual has to remain seated during this time so activity does not indirectly affect their heart rate. After fifteen minutes, the individual’s resting heart rate was taken three times. This process was repeated over the course of three days with different products each day to assure time for the caffeine to exit the system. Safety measures were taken when the participants were taking the pill; it was ensured that the right pill was being taken because the oval-shaped pill was light yellow in color with 200 written on one side of it.

Data Collection

The data that was collected prior to completing the experiment was qualitative through the use of the health survey. The data collected during the course of the experiment was quantitative by gathering the heart rates of the participant for each caffeine-based product that was consumed. The heart rates were collected a total of the three times to calculate an average before the caffeine-based product was consumed and fifteen minutes after being consumed.

The following table shows the results for each participant for the health survey:

The following data table shows the three trials and the average before and after the use of the caffeine pill for each participant:

The following data table shows the three trials and the average before and after the use of the NOZ Energy Drink for each participant:

The following data table shows the three trials and the average before and after the use of the Starbucks Espresso Energy Drink for each participant:

The following data table shows the change in heart rate for each participant for each caffeine-based product that was consumed:

Data Analysis and Conclusion

Participant T was a 30 year old who weighed 189lbs. Her daily caffeine intake was 15-30mg per day who maintained an adequate amount of activity or exercise. Participant only experienced a significant difference in heart rate with the NOZ Energy drink as some of the other participants. Despite Participant B having one of the lowest daily caffeine consumption levels, the results showed very little change unlike Participant D whose range was significantly high when the NOZ Energy drink was consumed. Participant B also had the highest decrease in heart rate when the caffeine pill was consumed. Participant P and Participant H showed little difference compared to the other participants with the products. This could be because they had built some form of tolerance to a level of caffeine because their daily caffeine intake was 60-200mg.

The data that was collected proved a part of the hypothesis that was posed. Heart rate increases or changes based on an individual and his/her health data. The participants who consumed minimal amounts of caffeine generally experienced a greater effect in the way caffeine affected their heart rate. The heart rates did increase when the participants consumed the caffeine products except for the caffeine pill. The caffeine pill was the only caffeine-based product that was not in liquid form so it may have affected the results. It would be important to find out how long it takes for the caffeine pill to dissolve as well as ensure the temperature of the water the participants take to ingest the pill is the same for future studies. It was expected that the Starbucks Espresso drink would increase the heart rate more than the NOZ energy drink based on the amount of caffeine per fluid oz (Starbucks – 19.2mg/fl oz, NOZ – 10mg/fl oz), but the NOZ proved to be more effective. It is also important to note that other ingredients in the products could have possibly influenced the heart rate as well. A future study could focus on whether or not the concentration of the caffeine and the ingredients is a factor. All the participants that were used in the study were female; in the future, the experiment can be expanded to include both men and women to see if a specific gender experiences greater effects of caffeine. Also, it would be important to complete a study including more variables such as breathing rate and blood pressure using the proper materials. Another study than can be used to expand this experiment is how caffeine withdrawals affect an individual based on the information regarding how long it takes for caffeine to be removed from the system.

References

All about heart rate (pulse). 2014. Retrieved October 20, 2014, from http://www.heart.or g/HEARTORG/Conditions/More/MyHeartandStrokeNews/All-About-Heart-RateP ulse_UCM_438850_Article.jsp

Nevins, P. Medications that increase heart rate. 2011. Retrieved October 20, 2014, fro m http://www.livestrong.com/article/152643-medications-that-increase-heart-rate/

Meininger, K. How caffeine affects heart rate. 2014. Retrieved October 20, 2014, from http://getfit.jillianmichaels.com/caffeine-affects-heart-rate-1220.html

Astrup A., Toubro S., Canon S., Hem P., Breum L., and Madsen J. (1990). Caffeine: a double-blind, placebo-controlled study of its thermogenic, metabolic, and cardiov ascular effects in healthy volunteers. The American Journal of Clinal Nutrition, 51(5), 759-767.