Insulin is a peptide hormone released from the pancreas in response to food being eaten. Insulin’s job is to carry the breakdown products of carbohydrate digestion – namely glucose in to the cells to be used for energy. Insulin also carries the breakdown products of protein digestion – namely amino acids in to the cells for a number of functions including protein synthesis. It seems that the breakdown product of fats in the diet – namely free fatty acids do not have an effect on insulin. Insulin can communicate with all manner of cells in the body – muscle cells, brain cells, liver cells and fat cells telling them to take in glucose and amino acids.
This mechanism works perfectly if there is a good balance of protein, fats and carbohydrates in the diet. The problem arises when there is excess carbohydrate in the diet, especially carbohydrates that release their glucose very quickly, which leads to sharp rises in blood glucose levels. Once the liver and muscle cells are full of the sugar they need insulin can no longer have an effect, however the fat cells happily take up the remaining sugar in the blood stream and an interesting thing happens. The glucose in the fats cells is metabolised to a substance called glycerol 3 phosphate, which in turn can be converted to triglycerides, essentially turning sugar in to fat.
In other words eating a high carbohydrate diet causes the release insulin and leads to the accumulation of fat in cells. Not only this but carbohydrate increases LDL cholesterol and triglycerides.
The research supports this, a study published in the Journal of the American Geriatrics Society demonstrated that fat intake was not associated with the condition metabolic syndrome – a condition that includes insulin resistance – but carbohydrate was. Another feature of metabolic syndrome is fatty liver – where fatty deposits accumulate in liver and cause damage. A study from the journal Gut demonstrated there was a significant increase in a liver enzyme called ALT, indicating liver damage that was associated to intake of carbohydrates, but not protein, fat or total calorie intake.
Not all carbs are the same
Now, not all carbohydrates are the same. Carbohydrate is an umbrella term that covers foods as diverse as fruit and vegetables, bread, potatoes, pasta, grains, chocolate, sweets and sugar. Obviously some of these carbohydrates are healthy – others are not. To help distinguish between healthy and unhealthy carbohydrates, three classifications of carbohydrates have been established – the Glycemic Index, Glycemic Load and the Insulin index. More on this tomorrow…