Dietary fat and carbohydrates are two of the major nutrients your body uses to generate caloric energy. The digestive system is responsible for breaking these nutrients down into their basic components, which are then absorbed and used as fuel or stored in the body. Although fat and carbs serve a similar function, these nutrients do not rely on each other for digestion. Each nutrient is metabolized by reacting with corresponding digestive enzymes produced in the body.
Digestive System
The food you eat follows a complex path through the body, entering at the mouth and exiting through the anus. Teeth begin the process of digestion by breaking food down into smaller components as you chew. The food is blended with the saliva in your mouth, then travels down the throat to into the esophagus, which deposits food into the stomach, where it is mixed with enzyme-rich digestive juices, cleared of harmful bacteria and further broken down. The small intestine reduces food to a thin, watery substance before releasing it to other areas of the body, while the liver and large intestine isolate waste products to be sent to the colon and rectum.
Carbohydrates
Carbs are broken down into basic building blocks, made of glucose, and are a faster source of energy than fats and proteins. Carb digestion takes place in saliva, pancreatic juices and the small intestine, where the enzyme amylase initially divides starch to form the simple sugar compound maltose. Simple sugars are then converted to absorbable glucose molecules by reacting with enzymes released from the lining of the small intestine. For example, the lactase enzyme is paired with lactose molecules, sucrase with sucrose and maltase with maltose. When you consume excess carbs, the body stores these molecules as fat or glycogen. Glycogen is an easily accessible energy source that the body relies on to sustain the muscles during intense exercise.
Dietary Fat
Fat is a complex mixture of fatty acids and glycerol, and as a result, passes through the body more slowly than carbs and proteins. Bile produced by the liver dissolves fat as the molecules blend into the watery substance in the small intestine. The pancreatic enzyme lipase then breaks down fat into its components and byproducts, including cholesterol. Modified compounds form as bile joins with fatty acids, helping to absorb the molecules into the intestinal lining for transport to other areas of the body. Fat is the densest provider of caloric energy, so the body maintains stores of this nutrient in the abdomen and beneath the skin to strengthen your body during periods of inadequate nutrition.
Complications
When your body fails to break down fats and carbohydrates properly, it can have a significant affect on your health. For example, various symptoms of conditions such as cystic fibrosis and celiac disease have been associated with low production of pancreatic enzymes. The University of Maryland Medical Center notes that treatments involving the oral ingestion of pancreatic enzymes helped overcome digestive limitations due to mucus buildup in saliva in patients with cystic fibrosis. Diabetes is another condition resulting from complications along the digestive tract. When the pancreas does not produce enough insulin, too much glucose passes into the bloodstream instead of being distributed throughout the body.
References
- Merck Manuals: Carbohydrates, Proteins and Fats
- Kids Health; "Your Digestive System"; June 2010
- National Digestive Diseases Information Clearinghouse; "Your Digestive System and How It Works"; April 2008
- University of Maryland Medical Center: Lipase
- "Nutrition"; Paul Insel et al; 2011
- PubMed Health: Diabetes
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