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Another Can of Bull?

Do Energy Drinks Really Provide a Source of Energy?

Cheryl D. Davis
Department of Biology
Western Kentucky University
Nancy A. Rice
Department of Biology
University of South Alabama


This case is a “clicker” adaptation of a similarly titled case by Merle Heidemann and Gerald Urquhart of Michigan State University, “A Can of Bull?” The story introduces students to basic principles of metabolism and energy through a biochemical analysis of commonly available “energy drinks” that many students purchase at relatively high prices. Students learn to define energy in a biological/nutritional context, identify valid biochemical sources of energy, discuss how foods are metabolized to generate ATP, and critically evaluate marketing claims for various energy drinks. The case can be used in introductory level courses to introduce these principles or as a review of basic biochemistry and nutrition for upper-level students in nutrition, physiology, or biochemistry courses. The case is presented in class using a PowerPoint (~2.3MB) that is punctuated by multiple-choice questions students answer using personal response systems, or “clickers.”


  • Define energy in a biological / nutritional context.
  • Identify valid biochemical sources of energy.
  • Discuss how foods are metabolized to generate ATP.
  • Critically evaluate marketing claims for various energy drinks.


Energy drink; metabolism; food energy; glycolysis; stimulant; caffeine; nutrient; calorie; Krebs cycle; oxidative phosphorylation; cyanocobalamin; ATP; Citrus Blast; Red Bull; Adrenaline Rush; Impulse; advertising; marketing claims

Educational Level

High school, Undergraduate lower division, Undergraduate upper division


PDF, PowerPoint

Type Methods

Clicker, Interrupted



Subject Headings

Biochemistry Nutrition Physiology Biology (General)

Date Posted


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Robert Skinner, PhD
Professor of Neurobiology and Developmental Sciences
University of Arkansas for Medical Sciences
Little Rock, AR 72205

I anxiously opened this case expecting to find how the amount of caffeine and other ingredients affect one’s health. But, I only found a discussion on sugar. I looked up the Wikipedia article on one of the drinks, Red Bull, and found that the high content of caffeine in it acts on the inner surface of blood vessels, the endothelial lining, and also interferes with normal blood coagulation. Small amounts of cocaine have been found in it. These seem more significant than calories. The caffeine makes you feel energized and more awake and the cocaine, if enough to have an effect, may reduce normal pain sensations. So, how about revising this case to show the potential detrimental effects of the ingredients other than sugars. I noticed in the Wikipedia article the recommendations for athletes to keep hydration and such power drinks are not recommended.

Authors’ Reply

The purpose of the case is really to get students to realize the difference between what serves as energy-producing compounds and what are stimulants. The role of trace amounts of cocaine is not within the scope of this case study.

Ann Taylor
Wabash College
Crawfordsville, IN
Slide 18 shows the hydrolysis reaction of ATP, stating it provides energy to do work...but the number given has a positive value, suggesting the reaction is either endothermic or endogonic (it's not indicated if the value represents delta H or delta G).