Download Summary of Chapter 4 – Lipids

Summary of Chapter 4 – Lipids
Lipids in the body not only serve as energy reserves but also protect the body from temperature extremes, cushion the vital organs, and
provide the major material of cell membranes.
The predominant lipids both in foods and in the body are triglycerides, which have glycerol backbones with three fatty acids attached.
Fatty acids vary in the length of their carbon chains and their degree of saturation. Those that are fully loaded with hydrogens are
saturated; those that are missing hydrogens and therefore have double bonds are unsaturated (monounsaturated or polyunsaturated). Most
triglycerides contain more than one type of fatty acid. Fatty acid saturation affects the physical characteristics and storage properties of
fats. Hydrogenation, which makes polyunsaturated fats more saturated, gives rise to transfatty acids, altered fatty acids that may have
health effects similar to those of saturated fatty acids. Linoleic acid and linolenic acid are essential nutrients. In addition to serving as
structural parts of cell membranes, they make powerful substances that help regulate blood pressure, blood clot formation, and the
immune response. Phospholipids, including the lecithins, have a unique chemical structure that allows them to be soluble in both water
and fat. In the body, phospholipids are major constituents of cell membranes; the food industry uses phospholipids as emulsifiers. Sterols
include cholesterol, bile, vitamin D, and the sex hormones. Only animal-derived foods contain significant amounts of cholesterol.
High intakes of saturated or trans fats contribute to heart disease, obesity, and other health problems. High blood cholesterol,
specifically, poses a risk of heart disease, and high intakes of saturated fat contribute most to high blood cholesterol. High intakes of
trans-fatty acids also appear to raise blood cholesterol. Cholesterol in foods presents less of a risk. Polyunsaturated fatty acids of the
omega-6 and omega-3 families protect against heart disease. When monounsaturated fat such as olive oil replaces saturated and trans fats
in the diet, the risk of heart disease may be lessened. Though some fat in the diet is necessary, health authorities recommend a diet
moderate in total fat, and low in saturated fat, trans fat, and cholesterol.
Fats in foods contribute to sensory appeal—enhancing the flavor, aroma, and texture of foods. Fats in foods deliver fat-soluble vitamins,
energy, and essential fatty acids. Though some fat in the diet is necessary, the Dietary Guidelines for Americans 2005 recommend
limiting fat intakes in order to limit intakes of saturated fat and trans fat. Fats added to foods during preparation or at the table are a
major source of fat in the diet. The choice between whole and fat-free milk products can make a big difference to the fat, saturated fat,
and cholesterol content of a diet. Meats account for a large proportion of the hidden fat and saturated fat in many people’s diets. Most
people consume more meat than is recommended. Most vegetables and fruits naturally contain little or no fat. Grain products such as
croissants and biscuits can be high in saturated fat, so consumers need to read food labels to learn which foods in this group contain fats.
Consumers today can choose from an array of fat-reduced products, and many bakery goods and other foods made with fat replacers
offer less than half a gram of fat, saturated fat, and trans fat in a serving. Some products use artificial fats such as olestra, while others
use conventional ingredients such as water or fat-free milk to reduce fat and kcalories. Food labels list total fat, saturated fat, cholesterol,
and trans fat, as well as fat kcalories, per serving.