Figure Websites With Reliable Nutrition Information

http://www.healthfinder.gov

This is a gateway to reliable consumer health and human services information developed by the U.S. Department of Health and Human Services. http://www.eatright.org

This is the website for the American Dietetic Association. It contains information on many nutrition topics and issues.

http://vm.cfsan.fda.gov

The Center for Food Safety and Applied Nutrition contains much information on food safety issues, nutrition labels, and other topics. http://www.usda.gov/cnpp

The Center for Nutrition Policy and Promotion of the USDA has the Dietary Guidelines for Americans and lots more nutrition information. http://www.nal.usda.gov/fnic

FNIC's (Food and Nutrition Information Center) website provides a directory to credible, accurate, and practical resources. FNIC is part of the USDA. http://www.foodandhealth.com

Food and Health Communications provides reliable nutrition information, as well as clip art, in many areas.

http://www.mayoclinic.com

This is the web site of the Mayo Clinic, which has much information on many health topics.

http://nccam.nih.gov

This is the website for the National Center for Complementary and Alternative Medicine.

http//www.acsm.org

This is the website for the American College of Sports Medicine. http://nutrition.gov

This government website has many links and much information.

they cannot establish that a particular factor causes a disease. This type of observational study may compare factors found among people with a disease, such as cancer, with factors among a comparable group without that disease or may try to identify factors associated with diseases that develop over time within a population group. Researchers may find, for example, fewer cases of osteoporosis in women who take estrogen after menopause.

A third type of research goes beyond using animals or observational data and uses humans as subjects. Clinical trials are studies that assign similar participants randomly to two groups. One group receives the experimental treatment; the other does not. Neither the researchers nor the participants know who is in which group. For example, a clinical trial to test the effects of estrogen after menopause would randomly assign each participant to one of two groups. Both groups would take a pill, but for one group this would be a dummy pill, called a placebo. Clinical studies are used to assess the effects of nutrition-education programs and medical nutrition therapy. Unlike epidemi-ological studies, clinical studies can observe cause-and-effect relationships.

When reading or listening to a news account of a particular study, it is helpful to have a few key questions in the back of your mind not only to help evaluate the merits of the study but also to determine whether it is applicable to you. Look to news reports to address the following:

  1. How does this work fit with the body of existing research on the subject? Even the most well-written article does not have enough space to discuss all relevant research on an issue. Yet it is extremely important for the article to address whether a study is confirming previous research and therefore adding more weight to scientific liefs or whether the study's results and conclusions take a wild departure from current thinking on the subject.
  2. Could the study be interpreted to say something else? Scientists often reach different conclusions when commenting on the same or similar data. Look for varying conclusions from experts, because certain issues they address may be important in putting the findings into context.
  3. Are there any flaws in how the study was undertaken that should be considered when making conclusions? The more experts are quoted or provide background in a news story, the more likely that potential flaws will be described.
  4. Are the study's results generalizable to other groups? Not all research incorporates all types of people: men, women, older adults, and people of various ethnicities. Also, a study may have been conducted on animals and not humans. If study results are applicable only to a narrow group of people, that should be reported as such.

Here are some websites that will help you separate fact from fiction:

www.quackwatch.com (Quack Watch) www.ncahf.org (National Council Against Health Fraud)

Figure 2-29 lists websites with reliable nutrition information.

Source: With permission, this Hot Topic used sections of "If It Sounds Too Good to Be True ... It Probably Needs a Second Look" from Food Insight, published by the International Food Information Council Foundation, March/April 1999.

urtesy oWRhotoDisc, Inc.

Carbohydrates

Carbohydrates

Functions of Carbohydrates

Simple Carbohydrates (Simple Sugars) Monosaccharides

Disaccharides Added Sugars Health Issues

Complex Carbohydrates

Starches

Health Effects of Starches Fibers

Health Effects of Fibers

Whole Grains

Digestion, Absorption, and Metabolism of Carbohydrates

Dietary Recommendations for Carbohydrates

Ingredient Focus: HighFiber Grains and Legumes

Grains

Chef's Tips Legumes Chef's Tips

Food Facts: The Facts about Low-Carb Foods

Hot Topic: Artificial and

Reduced-Kcalorie

Sweeteners

  • CARBOHYDRATE A large class of nutrients, including sugars, starch, and fibers, that function as the body's primary source of energy.
  • PHOTOSYNTHESIS A process during which plants convert energy from sunlight into energy stored in carbohydrate.
  • SIMPLE CARBOHYDRATES Sugars, including monosaccharides and disaccharides.
  • COMPLEX CARBOHYDRATES (POLYSACCHARIDES) Long chains of many sugars, including starches and fibers.

Carbohydrate LITERALLY MEANS HYDRATE (WATER) of carbon. The name was created by early chemists who found that heating sugars for a long period in an open test tube produced droplets of water on the sides of the tube and a black substance, carbon. Later chemical analysis of sugars and other carbohydrates indicated that they all contain at least carbon, hydrogen, and oxygen atoms.

Carbohydrates are the major components of most plants, making up 60 to 90 percent of their dry weight. In contrast, animals and humans contain only a small amount of carbohydrates. Plants are able to make their own carbohydrates from carbon dioxide in the air and water taken from the soil in a process known as photosynthesis. Photosynthesis converts energy from sunlight into energy stored in carbohydrates. The plant uses the carbohydrates to grow and be healthy. Animals are incapable of photosynthesis and therefore depend on plants as a source of carbohydrates. Plants, such as wheat and broccoli, supply the carbohydrates in our diets.

Carbohydrates are separated into two categories: simple and complex. Also called sugars, simple carbohydrates include sugars that occur naturally in foods, such as fructose in fruits and glucose in honey, as well as sugars that are added to foods, such as white sugar in a cookie.

Carbohydrates are much more than just sugars, though, and include the complex carbohydrates starch and fiber. Another name for complex carbohydrates is polysaccharides (poly- means many), a good name for starch and most fibers because both consist of long chains of many sugars.

After completing this chapter, you should be able to:

  • Identify the functions of carbohydrates
  • List important monosaccharides and disaccharides and give examples of foods in which each is found
  • Identify foods high in natural sugars, added sugars, and fiber
  • List the potential health risks of consuming too much added sugar
  • Identify food sources of starch and list the uses of starch in cooking
  • Distinguish between the two types of dietary fiber and list examples of food containing each one
  • Describe the health benefits of a high-fiber diet
  • Identify foods as being made from whole grains or refined grains
  • Describe how carbohydrates are digested, absorbed, and metabolized by the body
  • State the dietary recommendations for carbohydrates
  • Discuss the nutrition and use of grains and legumes in a menu

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FUNCTIONS OF CARBOHYDRATES

Carbohydrates are the primary source of the body's energy, supplying about 4 kcalo-

ries per gram. Glucose, a simple carbohydrate, is the body's number-one source of energy. Most of the carbohydrates you eat are converted to glucose in the body.

ries per gram. Glucose, a simple carbohydrate, is the body's number-one source of energy. Most of the carbohydrates you eat are converted to glucose in the body.

  • GLUCOSE The most significant monosaccharide; the body's primary source of energy.
  • GLYCOGEN The storage form of glucose in the body; it is stored in the liver and muscles.
  • KETONE BODIES A group of organic compounds that cause the blood to become too acidic as a result of fat being burned for energy without any carbohydrates present.
  • KETOSIS Excessive level of ketone bodies in the blood and urine.

Protein and fat can be burned for energy by our cells, but the body uses glucose first, in part because glucose is the most efficient energy source. The brain, spinal cord, and red blood cells are almost solely dependent on glucose as a source of energy.

Some glucose is stored in the liver and muscles in a form called glycogen. This way the body has a constant, available glucose source. Glycogen is stored in two places in the body: the liver and the muscles. An active 150-pound man has about 400 kcalories stored in his liver glycogen and about 1400 kcalories stored in his muscle glycogen. When the blood sugar level starts to dip and more energy is needed, the liver converts glycogen into glucose, which then is delivered by the bloodstream. Muscle glycogen does not supply glucose to the bloodstream but is used strictly to supply energy for exercise.

If you run out of glycogen and do not eat any carbohydrates, the body will break down protein in muscles to some extent. Protein can be converted to glucose to maintain glucose levels in the blood and supply glucose to the central nervous system. Carbohydrates spare protein from being burned for energy so that protein can be used to build and repair the body.

An inadequate supply of carbohydrates can cause the body to convert some fat to glucose, but this is also not desirable. When fat is burned for energy without any carbohydrates present, the process is incomplete and results in the production of ketone bodies. Ketone bodies can be used by the brain for energy, but too many can cause the blood to become too acidic (called ketosis), a condition that interferes with the transport of oxygen in the blood. Ketosis can cause dehydration and may even lead to a fatal coma. Carbohydrates are important to help the body use fat efficiently.

You need at least 100 to 150 grams of carbohydrates daily to prevent protein (and fat) from being burned for fuel and to provide glucose to the central nervous system (brain and spinal cord) and red blood cells. This amount represents what you minimally need, not what is desirable (about two times more). We obtain 50 to 60 percent of our energy intake from carbohydrates. Therefore, if you eat 2000 kcalories per day, you take in 1000 to 1200 calories of carbohydrates, which represents 250 to 300 grams.

Carbohydrates are part of various materials found in the body, such as connective tissues, some hormones and enzymes, and genetic material.

Fiber, a complex carbohydrate, promotes the normal functioning of the intestinal tract and is associated with a reduced risk of developing heart disease and type 2 diabetes (a disease characterized by high blood glucose levels).

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