Complex Carbohydrates – Polysaccharides

The polysaccharides are many units of monosaccharides held together by different kinds of chemical bonds. These types of bonds affect the ability of the body to digest polysaccharides and are the reason for the classification of polysaccharides as complex carbohydrates. There are two main types of complex carbohydrates, starch and fiber.

Starch, or starchy foods, all come from plant sources. Starch is the storage form of plant carbohydrate. The strings of glucose that form starch are broken down by the digestive tract to provide glucose. Food sources of starch include grains, legumes and some vegetables and fruits. Of the foods that provide complex carbohydrates grains are the best source for starch and provide more carbohydrates then any other food source. Grains include the following food types; wheat, oats, barley, rice, corn, and rye. The overall health value of processed grain products depends on their sugar, fat, and fiber content.

Breads, bagels, breakfast cereals, pasta, pancakes, grits, oatmeal and other cooked cereals provide high-quality complex carbohydrates. These grain products may also contain fiber if made with whole grains. Depending on the spreads and toppings served, they may also be low in fat. Main dish items such as pizza, rice, casseroles, and pasta mixtures create another category of complex carbohydrate foods. Other foods such as crackers, cakes, pies, cookies, and pastries also provide carbohydrates but often contain considerable amounts of added sugar and fats; they should be eaten in moderation.

Legumes, such as beans and peas, are another significant source of complex carbohydrates. They are low in fat and are also an excellent source of fiber, iron, and protein. Available dried, canned, or frozen, beans can be easily incorporated into commonly eaten foods.

Multicultural influences have expanded our exposure to inexpensive and versatile legumes. Mexican foods feature kidney beans as an ingredient of taco fillings and chili. Puerto Rico and Caribbean meals highlight rice and beans in savory sauces. Hearty Italian style soups often depend on white and kidney beans combined with pasta. An African influence is reflected in dishes that combine black-eyed peas with meats or green vegetables. Hummus, a chickpea paste dip of Middle Eastern Heritage, is often served with pita bread or vegetables.

Potatoes lead the way when it comes to vegetable sources of starch. We consume potatoes in many different ways and as a root vegetable the potato is unmatched in the amount of complex carbohydrates, fiber and vitamins it can provide. They even contain some protein. Unfortunately, some of the ways we prepare potatoes undo their positive health benefits. Most potatoes are processed into products loaded with fat and sodium. Nutritionally, potato chips have little in common with baked potatoes. The best health value is to eat potatoes in the least processed form. Instead of French fries, choose a baked potato or prepare mashed potatoes with skim milk and a small amount of margarine.

Other starchy root vegetables include parsnips, sweet potatoes, and yams. Sweet potatoes and yams provide the same nutrients as white potatoes plus significant amounts of beta-carotene. Carrots and some varieties of squash such as acorn and butternut also provide starch and beta-carotene. Beta-carotene, a substance the body can convert into vitamin A, may have a protective effect against some forms of cancer.

Fiber, like starch, also consists of strings of simple sugars. Unlike starch, however, human digestive enzymes cannot break down fiber. Dietary fiber consists of substances in plant foods including carbohydrates and lignin that, for the most part, cannot be digested by humans. We do not produce digestive juices strong enough to break down the bonds that hold the simple carbohydrates of most plant fibers, so fiber passes through our bodies without providing calories or nutrients. Its texture provides bulk that thickens chime and eases the work of the gastrointestinal muscles that regulate the movement of the food mass.

Although human digestive juices cannot digest fiber, micro flora that normally reside in the colon use fiber as a medium for microbial fermentation, resulting in the synthesis of vitamins and the formation of short chain fatty acids. The bacteria that reside in the colon synthesize several vitamins, including vitamin K, biotin, B12, folate, and thiamin. Only vitamin K and biotin can be absorbed in sufficient amounts from the colon to be significant; the other vitamins are absorbed from the small intestine so that the synthesized vitamins are not bioavailable. The short chain fatty acids that are produced can be absorbed and used for energy by the mucosa of the colon, thereby maintaining the health of the colon epithelial cells. Short chain fatty acids also increase fecal matter bulk.

Dietary fiber actually refers to several kinds of carbohydrate substances from different plant sources; all serve similar functions in the human body. Dietary fibers are divided into two categories based on their solubility in fluids. Soluble dietary fibers, which dissolve in fluids, include pectin, mucilage, psyllium seed husk, guar gum, and other related gums. Soluble fiber thickens substances. Insoluble dietary fibers do not dissolve in fluids and therefore provide structure and protection for plants. Some insoluble dietary fibers are cellulose and hemicellulose. Lignin, considered and dietary fiber, is composed of chains of alcohol rather than carbohydrate.

Foods are sometimes classified based on the predominate type of fiber they contain. Oatmeal is a good source of soluble fiber because oat bran, part of the whole oatmeal grain, is particularly high in soluble fiber. But the whole grain is a good source of insoluble fiber as well. Many fiber rich foods contain both soluble and insoluble fiber. An apple provides cellulose, an insoluble dietary fiber that forms the structure of the apple and gives it its apple shape. It also contains pectin, a soluble fiber that is part of the inside stuff of an apple.