What are Complex Carbohydrates?

Carbohydrates are classified as simple or complex. The classification depends on the chemical structure of the particular food source and reflects how quickly the sugar is digested and absorbed. Simple carbohydrates have one (single) or two (double) sugars while complex have more.

Examples of single sugars include fructose (found in fruits) and galactose (found in milk products). Lactose (found in dairy products), sucrose (table sugar) and maltose (found in certain vegetables) are double sugars.

Complex carbohydrates often referred to as starch, include foods like whole grain bread and cereals, starchy vegetables and legumes. Complex carbohydrates are made up of sugar molecules stuck together in long complex chains. These carbohydrates are turned into glucose in the body and are used as energy. Glucose is used in the cells of the body and in the brain. Any unused glucose is stored in the liver and muscles as glycogen for later use.

Complex carbohydrates foods provide vitamins, minerals, and fibre that are important to the health of an individual. The majority of carbohydrates should come from complex starches and naturally occurring sugars, rather than processed or refined sugars, which do not have the vitamins, minerals, and fibre that are found in complex carbohydrates. Refined sugars are often called “empty calories” since they have little or no nutritional value.

Carbohydrates must be digested and absorbed in order to transform them into energy that can be used by the body. Food preparation often helps in this digestion process. When starches are heated, they expand and thus making it easier for the body to break down.

The actual absorption starts in the mouth. The enzyme amylase, which is contained in the saliva, mixes with food products and breaks down some starches into smaller units. Once the carbohydrates reach the acidic environment of the stomach, the amylase is inactivated. After the carbohydrates have passed through the stomach and into the small intestine, key digestive enzymes are secreted from the pancreas and the small intestine where most of the digestion and absorption actually occurs.

Pancreatic amylase breaks down starch into disaccharides and smaller polysaccharides, and the enzymes of the small intestine wall break any remaining disaccharides into monosaccharides. Dietary fibre is not digested by the small intestine. Instead it passes to the colon unchanged and undigested.

Sugars such as galactose, glucose and fructose that are found naturally in the food or are prepared by the breakdown of polysaccharides enters into absorptive intestinal cells. After absorption, they are transported to the liver where galactose and fructose are converted to glucose and released into the bloodstream. The glucose may be sent directly to organs that require energy; it may be transformed into glycogen through the process known as glycogenesis for storage in the liver or muscles, or it may be converted to and stored as fat.