Changes of Heart Rate Due To the Consumption of Chocolate

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Changes of Heart Rate Due To the Consumption of Chocolate

How does the heart works? “The heart is a specialized muscle that pumps blood around the body. Blood carries oxygen and nourishment throughout the body and transports waste products to several organs to eliminate them. The heart is divided into two pumps which work together to make the heart work appropriately. Blood coming back from the organs and tissues of the body enters the right side of your heart which later pumps to the lungs. In the lungs the waste carbon dioxide from the blood is removed and blood is recharged with oxygen. The oxygen-rich blood returning from the lungs enters to the left side of the heart, which then pumps it to all the parts of your body, including the heart. This process ensures that the oxygen and nourishment is enough for the body to work efficiently.”(Heart Failure Matters) With this procedure, the heart can work perfectly and give the body enough oxygen to work properly in each activity humans perform. Yet, the way the heart works varies a lot, because of the people´s daily routine, age, medical treatment, or simply because of the type of food they consume. Normally the heart gives 50 to 100 beats per minute, but how fast or slow it beats depends on the amount of oxygen the heart needs. The amount of oxygen needed will depend on what humans consume, ingest and do with their organism.

There are many factors that affect the heart rate of a person. It can be during exercise or at rest. Those factors include exercise, medication and substances ingested. Not all humans do exercises, but all of them consume different substances, just like caffeine, at the time of eating breakfast or drinking something after a long day of work. “Caffeine has been implicated in a wide range of cardiovascular condition from heart disease to hypertension…Caffeine increases blood pressure within the first hours and will remain slightly higher for more than 2 hours.” (Goldberg pg. 247) Caffeine is found in different food adults, teenagers and kids eat. For example, coffee is mostly consumed by adults, and it contains high concentrations of caffeine which affects the way their heart work every day. Chocolate is another product highly consumed by teenagers and kids. This product contains cocoa, a powder made by cacao beans which have caffeine. Even though, chocolate contains caffeine, it affects the heart rate of a person in a good way.

Chocolate is one of the most famous candies in the world. The Theobroma Cacao is the tree used to produce this candy. It usually grows in hot, rainy tropics and need bigger trees to protect them from the wind and the sun. “Chocolate has a lot of versatile uses that fall outside of the traditional confectionary restrictions. In the past it has been used as a medicinal remedy and a currency; now it is sometimes molded into large chocolate sculptures or melted into chocolate fountains, or even used in extreme examples of fashion wear.” (Bradbury) This delicious candy has many uses but it has been settled as bad for the health of people, as well, due to all the components it has such as sugar, fat, caffeine, and cocoa, but in fact the chemicals it contains help the organism to work in a better way. Some of those chemicals are good for the heart, the brain, blood and other parts of the body.

There are different types of chocolates and all of them contain substances that help the organs. The most common types of are milk, dark and white chocolate. Dark chocolate helps blood to move faster throughout the brain and heart, which can improve the cognitive function. It also helps reduce the risks for stroke and contains chemical compounds that have positive effect in the person´s mood. One of those chemical compounds is phenylethylamine (PEA), which is the same element the brain produces when someone is starting to fall in love. PEA makes the brain reduce endorphins, making the person who is eating chocolate happier. Dark chocolate also contains theobromine[1], which has been proven to harden the tooth enamel, meaning that this type of candy can reduce the risk of having cavities as long as the consumer has a proper dental hygiene.[2] Sweet dark-chocolate and bittersweet chocolate have the similar benefits as dark chocolate due to the fact that they contain similar percents of cocoa. Milk chocolate doesn’t have the same benefits as dark chocolate, because it contains less amounts of cocoa, but it also helps the heart and brain, as well as the bones due to the addition of milk. “White chocolate is made from a mixture ofmilksolids, cocoa butter, and sugar. Unlike dark chocolate, it neither contains cocoa solids nor liquor. The reason why it has become popular than other types of chocolate is that it is free from caffeine.” (BenefitsOf) White chocolate is not really considered a pure chocolate due to the lack of cocoa; still it has cocoa butter, which is a replacement of real cocoa. It contains some of the compounds that help the body. White chocolate also has milk, which is a great source of calcium. This chocolate is perfect for people that can’t consume caffeine but still want to enjoy this candy. There also exist placebos[3] of chocolate made of vegetable oils, and fats with a physical quality just like cocoa butter, but don’t contain real cocoa. Sugar, coloring and flavoring are other ingredients added to make the placebo look and taste like real chocolate.

High amounts of caffeine may cause different heart rate irregularities, but chocolate doesn’t contain much of it. “Caffeine in chocolate that is unsweetened or is semi-sweet usually contains about five to 10 milligrams of caffeine per ounce of chocolate. Caffeine in chocolate with milk added is usually measured at five milligrams or less per ounce. Generally, caffeine in chocolate is present in higher amounts, as the chocolate gets darker.”(wiseGEEK) During the process of making chocolate, the amount of caffeine, contained in the cacao beans, is lowered due to the addition of other substances that have proteins and help the organism. A great example of this would be white chocolate, because it is not darker at all and the substances added do not contain real caffeine. Yet, it is not consumed frequently due to the addition of more sugar than the other types of chocolate. People tend to avoid eating too much chocolate due to the ideas they have such as that it causes acne, gives people headaches, hyperactivity and some allergies. Ingredients like sugar, fat and caffeine can affect the body, but chocolate also has ingredients that help our body work properly.

All chocolates contain cocoa in high or low amounts and that’s the powder that has all the benefits, this delicious candy provides to consumers. “The cocoa flavanols[4] are able to limit the progressions of cardiovascular diseases by exerting anti-platelet (anti-blood clotting), anti-inflammatory and antioxidant activities. (Beckett pg. 205) Flavanols work as antioxidants in the body, meaning that chocolates with high levels of flavanol can help the organism to prevent many diseases. All chocolates, especially dark chocolate, contain antioxidants, nutrients and vitamins the body needs, so eating a chocolate can help the body to be healthy. Those antioxidants help to stimulate the immune system of cells. Flavanoids are consumed in chocolate, which decreases risks of heart attack or other heart diseases.

Yet the consumption must not be exceeded, because not all the ingredients of chocolate are good, such as cholesterol, which in high levels can affect the body, or fat, which can make a person increase their weight. Calories in high amounts increase the weight of the body, making some organs not work in the right way. As mentioned before, chocolate has certain amounts of caffeine, and as it gets darker more caffeine it has, so its consumption must be balanced, so the body doesn’t get affected by it.

With this experiment we want to test how does chocolate affect the heart rate of the students of The Notre Dame School? The students will be exposed to different types of chocolate with different amount of ingredients, to find out which one affects the most their heart rate. We will determine if chocolate does or doesn’t affect the heart rate of those students. The universe of this experiment will be 16-17 year old students, with healthy hearts and body. The students´ heart beats will be measured with a heart rate monitor. “A typical heart rate monitor consists of several useful functions. The average heart rate function lets you know your total average heart rate from the moment you first turn the receiver on until you turn the receiver off. Two of the most important benefits of using a heart rate monitor are the accuracy and ease of using and measuring your heart rate during exercise. The heart rate monitor is capable of hands-free operation and therefore is more accurate.” (Spickler) A heart rate monitor is usually used to measure the pulse of people during exercise, but in this experiment it will be used to see the changes of heart beat after consuming chocolate. Heart rate monitors are more accurate, because they measure heart beats at every moment, letting you know how fast or slow you heart is working. With this apparatus, people no longer have to try to find their pulse with their hands, which can be difficult, so it will be easier to perform this experiment and be precise.


If different types of chocolates are given to 16-17 year old students, then dark chocolate will increase the heart beats in a better way, because it contains high concentrations of cocoa which is a stimulant that will help the blood travel around the heart and brain in a faster way, making it work better.


Independent: Types of Chocolate given

  • Dark chocolate
  • White Chocolate
  • Milk Chocolate
  • Sweet dark-chocolate
  • Bittersweet Chocolate
  • Single Bean Chocolate
  • Placebo

Dependent: How many heart beats are produced after students consume chocolate (this will be measured using a heart rate monitor)


  • Amount of chocolate given (40g)
  • Heart rate monitor (the same apparatus will be used the heart beat of all students to make sure, they get accurate results)
  • Age of students (16-17 years old)
  • Amount of time we let chocolate make the reaction (7 min)

Materials and Method:


  • Chocolate (7 different types of chocolate)
  • Heart rate monitor ( )
  • Chronometer
  • 16-17 year old students (30 people)
  • Notebook
  • Same environmental conditions
  • Same room temperature


  1. First, use the heart monitor to calculate the normal heart beat of each student.
  2. Then, cut one type of chocolate in 14 pieces of 16g each. (14 pieces because the population of this experiment is of 14 students).
  3. Make each student eat a piece of chocolate.
  4. Wait for 5 minutes for the chocolate to make any reaction in the circulatory system
  5. Calculate the heart beats of each student with the heart monitor.
  6. Record results and determine the difference of heart beats made by each person before and after eating the chocolate
  7. Repeat steps 2 – 6 with the 7 different types of chocolate.

(It is better to work out the experiment with one student at the time due to the amount of time it takes for each chocolate to react and for the reaction to come to an end.)



  • Anonymous. “How Does the Normal Heart Works?” Heart Failure Matters. January 8, 2014.WEB.


  • Bradbury, Kate. “Uses of Chocolate.” Chocolate Expert. 2000-2014. October 11, 2012. January 8, 2014. WEB.


  • Spickler, Brian. “What Does a Heart Rate Monitor Measures.” November 10, 2013. January 9, 2014. WEB.




  • "Placebo."The American Heritage® Dictionary of the English Language, Fourth Edition. 2003. Houghton Mifflin Company 26 Feb. 2014


  • Anonymous. “Heart Health Benefits of Chocolate.” Cleveland Clinic. 1995-2014. January 9, 2014. WEB.



  • Goldberg, Raymond. “Drugs Across The Spectrum.” 2010. Yolanda Cossio.PRINT.
  • Beckett S.T. “The Science of Chocolate.”Great Britain. Royal Society of Chemistry.2008. PRINT.

[1] Theobromine:

diureticdrugandmajoralkaloidalconstituentofcocoa.Theobromine isaxanthinealkaloid, amethylxanthine,asarecaffeineandtheophylline,butitdiffersfromtheminhavinglittlestimulatory actionuponthecentral nervous system. <>

[2] FitDay.


[3] Placebo:

An inactive substance or preparation used as a control in an experiment or test to determine the effectiveness of a medicinal drug. <>

[4] Flavanol: the main type of flavonoid found in chocolate and cocoa. Flavonoidshelp protect plants from environmental toxins and help repair damage…it appears that we also benefit from this "antioxidant" power. <>