Digestion helps the body absorb nutrients from food for nourishment, energy and cell tissue repair, according to the National Institute of Diabetes and Digestive and Kidney Diseases, or NIDDK. Food must be broken down by digestive enzymes before the molecules can enter the bloodstream to deliver essential nutrients to cells.
Digestive organs extract carbohydrates, proteins, fats, vitamins and minerals from food. Carbohydrates in fruits, vegetables and grains are broken down into simple sugars and absorbed into the bloodstream for energy, changing the body's blood sugar level, according to the Merck Manual Home Health Handbook. Fluctuations in blood sugar influence hunger and insulin production.
Carbohydrates also contain fiber, which the body does not digest. Fiber satisfies hunger by slowly passing through the digestive tract, and it aids waste in moving through the digestive and excretory systems, as explained by MedlinePlus.
Proteins are broken down into amino acids, mixed with digestive juices and absorbed through the lining of the small intestine, according to the NIDDK. The bloodstream carries protein molecules throughout the body to stimulate cell growth and repair damaged tissue, as explained by the Merck Manual Home Health Handbook.
The pancreas and liver release enzymes to extract fatty acids and glycerol from fats. Some fat molecules are converted to energy, and others are used to absorb and store vitamins, according to the NIDDK. When a person consumes too many carbohydrates or proteins, the excess molecules are also converted to fats and stored in the cells to use as energy in the future, according to the Merck Manual Home Health Handbook.