Nutrients and normal blood sugar control

The body needs three main nutrients to function properly—carbohydrate, protein, and fat. These nutrients are digested into simpler compounds. Breads, grains, vegetables, and sugary foods are carbohydrate that is converted to glucose, one of many types of sugar molecules produced when carbohydrate is digested in the stomach and intestines. Similarly, the body breaks down protein into amino acids and fat into fatty acids, all to store energy for the body.

After a meal, the blood sugar (glucose) level rises as carbohydrate is digested. This stimulates the beta cells of the pancreas to release insulin into the bloodstream. Insulin helps glucose enter the body's cells to be used for energy. If all the glucose is not needed for energy, some of it is stored in fat cells and in the liver as glycogen. As sugar moves from the blood to the cells, the blood glucose level returns to a normal between-meal range.

Several hormones and processes help regulate the blood sugar level and keep it tightly within a safe range (80 mg/dL to 120 mg/dL). When the blood sugar level falls below the desirable range, which may happen between meals, the body has at least three ways of responding:

• Cells in the pancreas release glucagon, a hormone that stimulates the body to produce glucose from glycogen in the muscles and liver and release it into the blood.
• Once glycogen is used up, muscle protein itself is broken down. The liver uses the resulting amino acids to create glucose through a series of biochemical reactions (gluconeogenesis).
• Fat stores are also used for energy, forming compounds called ketones.

Other hormones may also intervene to raise the blood sugar level, including epinephrine (also called adrenaline) and cortisol released by the adrenal glands and growth hormone released by the pituitary gland.