Unit 2
General Principles of Research in Nutrition

Nutrition is a rapidly expanding science. The last 25 years have seen an explosion of knowledge in the area. Often, though, today’s “discovery” is tomorrow’s discredited idea. For example, the role of dietary factors affecting colon cancer (fat), the common cold (vitamin C), obesity (a high energy intake), and hyperactivity (food additives) have been both “proven” and “disproven.” Why is there such confusion? The perennial problem of nutrition is that it is not an exact science: rarely does it have the precision of physics or chemistry. Nutrition science is often like a mystery, where clues are gathered from many sources. Nutrition researchers may not be able to use scientific research methods that provide direct evidence through “gold standard” intervention trials.

In this unit, we look at how nutrition research is conducted to enable you to make your own assessment of claims and to sort the wheat from the chaff.

The main part of this unit explains different nutrition research methods, including a discussion of the advantages and disadvantages of each method.

Objectives

After completing this unit, you should be able to

1. describe types of studies used in establishing the role of diet in disease and their advantages and disadvantages. These studies include epidemiological studies (including population, historical, case-control, and cohort studies), intervention studies, animal studies, biochemical and physiological studies, as well as anecdotal evidence.
2. determine whether each type of study shows causality or association, and describe the potential for incorporating study conclusions into nutrition recommendations.
3. discuss at least five factors of a well-balanced intervention study.
4. assess nutrition information for reliability.