Chapter 5 Summary

5.7 Carbohydrates and Health

Eating fiber-rich foods may reduce your risk of obesity, type 2 diabetes, cardiovascular disease, and certain intestinal tract disorders. High-fiber diets, especially those with ample amounts of insoluble fiber, are associated with lower risk of constipation and hemorrhoids compared to diets that contain little fiber. Additionally, foods that contain soluble fiber may improve cardiovascular health by reducing cholesterol absorption. Plant foods generally contain both forms of fiber.

5.7 Carbohydrates and Health

Foods that contain a lot of added sugars and fats tend to be energy dense. Some nutrition scientists think high intakes of added sugars, especially in regular soft drinks, is largely responsible for Americans' rising rate of obesity.

5.4 What Happens to Carbohydrates in the Body?

Glucose is the primary end product of carbohydrate digestion. Hormones, particularly insulin and glucagon, maintain normal blood glucose levels. Insulin enables glucose to enter cells, where the sugar is metabolized for energy. Glucagon stimulates the liver to break down glycogen into glucose molecules and release them into the bloodstream.

5.1 Introducing Carbohydrates

Carbohydrates are an important source of energy for the body. Plants use energy from the sun to make carbohydrates from water and carbon dioxide. Some of the energy is stored in the bonds that hold the carbon and hydrogen atoms together. Cells break down those bonds, releasing the energy that powers various forms of cellular work.

5.7 Carbohydrates and Health

Diabetes mellitus is characterized by elevated blood glucose levels. Diabetes can result in cardiovascular disease, kidney failure, blindness, and lower limb amputations. There are two major types of diabetes mellitus, type 1 and type 2 diabetes. Type 2 diabetes is the more common form of the disease. People who are sedentary, have excess body fat, eat Western diets, and have a close relative with type 2 diabetes are at risk of developing this form of the disease.

5.5 Carbohydrate Consumption Patterns

People in industrialized nations tend to eat less complex, unprocessed carbohydrates and more highly refined sugars than people living in less-developed countries. Healthy Americans should consume diets that furnish 45 to 65% of energy from carbohydrates, primarily complex carbohydrates. Refined sugar is often blamed for causing obesity, diabetes, and hyperactivity, but tooth decay is the only health problem that is clearly associated with eating carbohydrates. Many adults are lactose intolerant because they do not produce enough lactase, the intestinal enzyme needed to digest the disaccharide.

5.3 Complex Carbohydrates

Starch, glycogen, and most forms of dietary fiber are polysaccharides. Although fiber is not digested by humans, soluble and insoluble fiber provide important health benefits.

5.6 Understanding Nutrient Labeling: Carbohydrates and Fiber

The Nutrition Facts panel provides information about total carbohydrate, sugars, and fiber contents of packaged foods and beverages.

5.8 Nutrition Matters: Glycemic Index and Glycemic Load

The glycemic index (GI) and glycemic load (GL) are ways of classifying certain foods by their effect on blood glucose levels. Results of some epidemiological studies suggest an association between high GI/GL diets and serious chronic diseases. However, more long-term research is needed before nutrition experts recommend low GI or low GL diets for the general population.

5.2 Simple Carbohydrates: Sugars

The three most important dietary monosaccharides are glucose, fructose, and galactose. Glucose is a primary fuel for muscles and other cells; nervous system and red blood cells rely on glucose for energy under normal conditions. Lactose and sucrose are major dietary disaccharides.