Unit 3 – The Science of Nutrition

3.1 Introduction

Life is extraordinarily complex. That’s true whether you’re considering something as seemingly simple as a blade of grass or as complicated as the human body. However, when we feel the makeup of living things—from atoms to molecules to macromolecules to cells—we can see similarities and patterns that help us make sense of this complexity.


In this unit, you’ll learn about the scientific method because it forms the foundation for knowing what we know about nutrition. You’ll learn about the different types of research studies and their advantages and limitations. We’ll discuss various sources of information, such as scholarly and popular sources, how each can be useful in different ways, and how to evaluate them. We’ll also discuss careers in nutrition and the different types of skills that you’ll find among nutrition experts.


Because understanding nutrition requires a bit of chemistry and biology, we quickly review atoms and molecules,  the simplest substances in food and our bodies, then move to cells. Understanding these is required to appreciate how the human body uses nutrients.  The last sections of this unit focus on the digestive system, the site of food processing and nutrient extraction. And while it usually functions as an efficient and coordinated system, we’ll also consider some common ways that it can go awry, resulting in disorders and discomforts of the digestive tract or adverse reactions to certain foods.

Unit Learning Objectives

After completing this unit, you should be able to:

  1. Identify the sequential steps of the scientific method, and understand the importance of reporting research results in peer-reviewed journals.
  2. Describe the different types of research studies used in nutrition, including the quality of evidence, advantages, and limitations of each.
  3. Be aware of some of the limitations of nutrition research, including the challenges of studying complex dietary patterns and the influence of industry funding.
  4. Understand the differences between scholarly (peer-reviewed) and popular sources for nutrition information.
  5. Evaluate sources of nutrition information and distinguish between credible sources and junk science.
  6. Identify the qualifications of nutrition professionals and career opportunities in nutrition.
  7. Define and describe the levels of structural organization of the human body—from atoms and molecules to the whole organism—including the essential characteristics of cells
  8. Recognize the basic structure of molecules and that all nutrients are also chemical molecules.
  9. Identify and briefly describe the functions of the organs of the gastrointestinal (GI) tract, and discuss the five fundamental activities of digestion, giving an example of each.
  10. Describe several common disorders and discomforts of the GI tract, including their causes, symptoms, and approaches to treatment.


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Introduction to Nutrition and Wellness Copyright © 2022 by Janet Colson; Sandra Poirier; and Yvonne Dadson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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