Unit 6
The Lipids: Fats, Oils, Phospholipids, and Sterols

Dietary lipids have gained much attention in recent years because of growing evidence of their association with chronic lifestyle diseases such as heart disease, cancer, and obesity. Despite bad press, dietary lipids have an essential role. They provide the most concentrated form of energy (nine kilocalories per gram of fat) and are the source of essential fatty acids and omega-3 fats, EPA, and DHA. As with all nutrients, over-consumption of lipids will result in adverse health effects. In our affluent society, most people tend to consume too much fat—especially the types that may contribute to chronic diseases.

In this unit, we examine the chemical and physical characteristics of various types of lipids and discuss their sources. While there are over 50 types of fatty acids in the diet, this unit will focus on 10 of them. We will study the processes of digestion, absorption, and transport of lipids, and review the functions of lipids and the effects of diet on blood cholesterol. Then, we will look at trends in fat consumption by Canadians, the current recommendations for fat intake, and the effects of food processing on dietary lipids.

Objectives

After completing this unit, you should be able to

1. identify the chemical characteristics of triglycerides, phospholipids, and sterols.
2. describe seven functions of lipids in the body.
3. describe the process of digestion, absorption, and transport of dietary lipids.
4. identify the two families of essential fatty acids.
5. describe nine roles of essential fatty acids.
6. describe the problem of lipid oxidation, and explain how it can be prevented.
7. discuss three purposes for hydrogenating fats and four nutritional composition changes resulting from hydrogenation.
8. identify the major sources of different types of dietary lipids and fatty acids discussed in this unit.