Insulin is a hormone produced by the pancreas and is central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen inside these tissues. In addition, Insulin stops the use of fat as an energy source and promotes glucose storage as fat
Insulin is provided within the body in a constant proportion to remove excess glucose from the blood, which otherwise would be toxic. The release of Insulin is rapidly triggered in response to increased blood glucose levels. When the glucose level comes down to the usual physiologic value, insulin release slows or stops. Meanwhile stress and stimulation of the sympathetic nervous system inhibits the release of insulin.
Tissues most strongly influenced by insulin and its effect in the stimulation of glucose uptake: muscle cells (myocytes) and fat cells (adipocytes). The former are important because of their central role in movement, breathing, circulation, etc., and the latter because they accumulate excess food energy against future needs
The actions of insulin (indirect and direct) on cells include:
- Increased glucose uptake from blood and increased synthesis of glycogen (the storage form of glucose)
- Increased fat and triglyceride uptake from the blood and increased synthesis of triglycerides in cells (adipose tissue)
- Decreased breakdown of protein, decreased breakdown of fat cell lipid stores into blood fatty acids, decreased breakdown of glycogen to glucose (gluconeogenesis )primarily in the liver
- Increased amino acid uptake by cells, increased potassium uptake from the blood, and increased relaxation of arterial wall muscles to relax which increases blood flow, especially in microarteries
- Increase in the secretion of hydrochloric acid by cells in the stomach and decreased excretion of sodium via the kidneys
Insulin Sensitivity occurs when all the functions of insulin are working. Thus, following dietary carbohydrate intake, the following occur due to insulin release into the blood:
- Sugar is taken up by the liver. Excess sugar is converted to triglycerides, cholesterol and glucagon
- Triglycerides and cholesterol are taken up by various cells in the body. Sugar is also taken up by cells.
- When all the sugar and fats are in the cells, blood sugar levels start to drop and insulin levels go back down. As a result, insulin levels rise after a meal and come back down again in between meals
After a high carbohydrate meal, excess insulin may be excreted leading to rapid uptake of sugar and fat into cells. This leaves less sugar in the blood, causing a rapid and dramatic drop in insulin levels (symptoms of hypoglycaemia and fatigue may result from the excess insulin being released)
The more insulin levels fluctuate high-highs and low-lows, the following symptoms are evident:
- Clammy skin; Heart palpitations; Insommnia; loose bowel movements
- Fatigue; foggy thinking; irritability; light-headedness; panic attacks; sugar cravings
Schwarzbein, D.(2002). The Schwarzbein Principle II: The Transition. Deerfield Beach, Florida, Health Communications, Inc.