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The insulin index is a way of quantifying the amount of insulin that the body produces in response to a variety of foods. This concept is similar to the glycemic index, which calculates the rise in blood sugar, or blood glucose levels, induced by certain foods. First introduced in a 1997 article published by the American Journal of Clinical Nutrition, the insulin index was the work of a graduate student, Susanne Holt, at the University of Sidney. Basically, 38 foods were fed to healthy study participants, finger blood samples were taken every 15 minutes for the following two hours, and insulin levels were measured at each time point.
Although there is a high correlation between the glycemic index and the insulin index measurements, there are some exceptions. Several high protein foods that measured low on the glycemic index measured high on the insulin index. Examples of such foods with discrepant glycemic and insulin measurements include milk, yogurt, cheese, beef, fish, and baked beans.
The rise in insulin levels after a protein-rich meal is explained by the fact that insulin is a hormone that promotes the storage of nutrients. Although insulin is best known as the hormone released in response to a high carbohydrate meal to signal certain tissues to take up glucose from the blood, the body also releases insulin as a signal to store ingested protein. Insulin induces the uptake of amino acids, which are the breakdown products of proteins, for storage in tissues.
Insulin resistance means that a person’s cells have a lowered capacity to respond to insulin, so there will be a generally reduced level of glucose transport from the blood to the tissues. Many issues can cause insulin resistance, such as pregnancy, certain prescription drugs, smoking, and even a high stress lifestyle. This condition is usually first treated with lifestyle changes but may eventually require medication if the situation does not improve.
The insulin index may be most useful for people who have, or are in danger of developing, insulin resistance. While many people with insulin resistance probably avoid the foods that have classically been associated with insulin release, such as foods and drinks high in sugar, many of these same people may not realize that high-protein foods can also cause a rise in insulin levels. For these people, the insulin index can help guide them as to which additional foods they should avoid. Finally, because excessively high insulin levels are associated with a higher risk of developing serious conditions such as heart disease, the insulin index can guide people with insulin resistance on which foods to avoid, or eat sparingly, to ensure their best health.