Page 3 of 12



macronutrients link to fats link to carbohydrates link to protein
Click on the macronutrient above to jump to that section.
Carbohydrates are simple hydrocarbon chains in various lengths. Simple carbohydrates are mono and disaccharides - glucose, fructose, galactose, maltose, and sucrose. Complex carbohydrates are comprised of long chains of mono and disaccharides connected to form polysaccharides (starches and dietary fiber). The only difference between starches and dietary fibers is that humans lack the necessary enzymes required to break the beta linkages of fiber versus the alpha links connecting starches (alpha amylase vs. beta amylase). Carbohydrates yield approximately 4 kilocalories per gram and function in the body mainly as the primary source of energy. The brain and central nervous system can only use glucose as an energy source. How much carbohydrate do we need? It's estimated that approximately 100 gms of carbohydrate is required on average per day to prevent breakdown of protein to be used as energy (protein-sparing effect). What would you need to eat to get a minimum of 100 grams? Most of the world's populations ingest a carbohydrate- based diet for good reason - it's a readily available, inexpensive source of energy.

The case for fiber is not nutritional per se as it is indigestible. Fiber serves a number of functions, notably providing bulk to the stool, functioning as a substrate for healthy gut flora, and satiety in terms of hunger. Fiber can be classified into insoluble and soluble. Insoluble fibers act like sponges to absorb water and bulk up the stool. Have you ever seen bran in a bowl of milk after awhile? Insoluble fibers are beneficial to the GI tract in terms of increasing motility, diluting and promoting the exit of toxins in the gut, and preventing constipation, hemorrhoids, and the development of diverticulum.

foodGood sources of insoluble fiber include whole grains and wheat bran, raw fruits and vegetables, nuts, and seeds. Soluble fibers form gels in the gut and are useful in regulating stool consistency for both diarrhea and constipation. They also help lower blood cholesterol and slow the absorption of simple carbohydrates.

foodGood sources of soluble fibers are raw fruits and vegetables, dried beans and peas, foods containing pectin such as apples, gums, oat and rice bran, and psyllium seed.

Clinical Point: Whenever anyone is ingesting large amounts of fiber, soluble or insoluble, fluid intake needs to be increased to prevent ileus. Fiber should be increased gradually in the diet to avoid unpleasant side effects.

color bar

Content questions should be directed to: Marilyn.S.Edwards, Ph.D., R.D.
or Maggie McQuiggan, M.S.
Copyright © 2004 - present
, All Rights Reserved.
The University of Texas Health Science Center at Houston
Created by Beth Ardoin, M.Ed. in Academic Technology's Multimedia Scriptorium