Defining Nutrition, Health, and Disease

Learning Objectives

  1. Define health, nutrition, and disease.
  2. List and describe the characteristics used to assess your health status.
  3. Differentiate among risk factors, signs, and symptoms.
  4. Define the word “nutrient” and differentiate among the six classes of nutrients essential for health.
  5. Explain how energy values of food are determined, and list the three energy-yielding nutrients and their energy contribution.
  6. Describe measures of food quality and be able to calculate and compare energy densities of foods.
  7. Describe the importance of research and scientific methods to understanding nutrition.
  8. Analyze sources of nutrition information for reliability and credibility.

Life depends on nourishment and the quality of life depends greatly on the foods you choose to eat. Any discussion of nutrition must begin with an understanding of nutrition, nutrients, and their overall relationship to health and well-being.

Defining Nutrition, Health, and Disease

The word nutrition first appeared in 1551 and comes from the Latin word nutrire, meaning “to nourish.” Today, we define nutrition as the sum of all processes involved in how organisms obtain nutrients, metabolize them, and use them to support all of life’s processes. Nutritional science is the investigation of how an organism is nourished, and incorporates the study of how nourishment affects personal health, population health, and planetary health. Nutritional science covers a wide spectrum of disciplines. As a result, nutritional scientists can specialize in particular aspects of nutrition such as biology, physiology, immunology, biochemistry, education, psychology, sustainability, and sociology.

Without adequate nutrition the human body does not function optimally, and severe nutritional inadequacy can lead to disease and even death. The typical Canadian diet contains adequate calories, but is lacking in many ways, from not containing the proper amounts of essential nutrients, to being too speedily consumed, to being only meagerly satisfying.

Nutrition and Health and Disease

Your ability to wake up, to think clearly, to communicate, to hope, to dream, to go to school, to gain knowledge, to go to work, to earn a living, and to do all of the things that you like to do are dependent upon one factor—your health. Good health means you are able to function normally and work hard to achieve your goals in life. In 1946, the World Health Organization (WHO) defined health as “a state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity.”[1] This definition was adopted into the WHO constitution in 1948 and remains to this day. A triangle is often used to depict the equal influences of physical, mental, and social well-being on health.

Disease is defined as any abnormal condition affecting the health of organisms and typically characterized by specific signs and symptoms. Diseases are broadly categorized as resulting from pathogens (i.e., bacteria, viruses, fungi, and parasites), deficiencies, genetics, and/or physiological dysfunction. Diseases that primarily affect physical health are those that impair body structure (as is the case with osteoporosis), or functioning (as is the case with cardiovascular disease). Mental illnesses primarily affect mental and social well-being.

The foods we eat affect multiple aspects of our health. For example, a teen with type 2 diabetes (a disease often brought on by poor diet and lack of physical activity) is first diagnosed by physical signs and symptoms such as increased urination, excessive thirstiness, and unexplained weight loss. But research has also found that teens with uncontrolled type 2 diabetes often have impaired thinking and may not interact well with others in school, thereby affecting mental and social well-being. This is just one example of a physiological disease that can affect physical, mental, and social aspects of health.

In the early twentieth century, most nutrition-related diseases and conditions were related to inadequate calorie consumption or deficiency of nutrients. In the latter part of the twentieth century nutrition scientists, public health organizations, and the Canadian public increasingly recognized that eating too much of certain foods is linked to chronic diseases.

The table below shows the top ten causes of death in Canada. As you can see, many of these causes are related to nutrition. We now know that diet-related conditions and diseases include but are not limited to cardiovascular (heart) diseases including hypertension (high blood pressure) and stroke, obesity, type 2 diabetes, several forms of cancer, and osteoporosis.

Canada: Top 10 Leading Causes of Death (2019 to 2022)[2]
 2019  2020  2021  2022  2019  2020  2021  2022
Number of Deaths Number of Deaths Number of Deaths Number of Deaths Rank Rank Rank Rank
Malignant neoplasms(cancer) 80372 81242 82822 82412 1 1 1 1
Diseases of heart 53364 54430 55271 57357 2 2 2 2
COVID-19 15890 14466 19716 4 4 3
Accidents (unintentional injuries) 15527 16818 19257 18365 3 3 3 4
Cerebrovascular diseases 13717 13761 13491 13915 4 5 5 5
Chronic lower respiratory diseases 12902 11844 11018 12462 5 6 6 6
Diabetes mellitus 6987 7654 7472 7557 6 7 7 7
Influenza and pneumonia 6945 6037 4115 5985 7 8 10 8
Alzheimer’s disease 6181 5788 5471 5413 8 9 8 9
Chronic liver disease and cirrhosis 3708 4199 4617 4530 11 10 9 10
Nephritis, nephrotic syndrome and nephrosis 3770 4065 3978 4234 10 12 11 11
Intentional self-harm (suicide) 4581 4152 3769 3593 9 11 12 13
Other ill-defined and unspecified causes of mortality 3378 6841 9471 16043
Total, all causes of death 285301 308412 311640 334081

references

Chapter 1, section 1.1 from Consumer Nutrition by Megan Grimsley and Susan Kazen published in 2021 under a CC BY-NC-SA license.

Author Notes
Portions of this chapter were taken from OER Sources listed below:

Tharalson, J. (2019). Nutri300:Nutrition. https://med.libretexts.org/Courses/Sacremento_City_College/SSC%3A_Nutri_300_(Tharalson)

Titchenal, A., Calabrese, A., Gibby, C., Revilla, M.K.F., 7 Meinke, W. (2018). Human Nutrition. University of Hawai’i at Manoa Food Science and Human Nutrition Program Open Textbook. https://pressbooks.oer.hawaii.edu

Zimmerman, M., & Snow, B. (2012). An Introduction to Nutrition, v. 1.0. https://2012books.lardbucket.org/books/an-introduction-to-nutrition/


  1. World Health Organization. (1946). Preamble to the Constitution of the World Health Organization as adopted by the International Health Conference. Official Records of the World Health Organization. https://www.who.int/about/who-we-are/constitution
  2. Statitics Canada. (2023, November 27). Top 10 leading causes of death (2019 to 2022). https://www150.statcan.gc.ca/n1/daily-quotidien/231127/t001b-eng.htm
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