Insulin Index (IS)

Insulin Index (IS) – determines the insulin response to a product, the energy of which equals 1000 kJ i.e. 239 kcal. This indicator is much more practical because it does not refer to the blood sugar concentration but directly to the concentration of blood insulin.

Insulin is a hormone secreted by the pancreas. It is essential for our body because it regulates blood sugar. If the level of blood glucose is too high, insulin is released, to redirect glucose into cells. Glucose can be stored both in muscles and liver as well as in the adipose tissue.

After consuming carbohydrates with high glycemic index (GI), there is a significant increase in blood insulin. By analogy, it could be assumed that low glycemic index products will cause a small increase in insulin levels and that fat and protein products will not rise this level at all.

Hence, there was a widespread belief that:

• high GI of the product = high increase in insulin level,
• low GI of the product = slight increase in insulin level.

Not really. This thesis was disproved by a group of Austrian scientists who developed the so-called insulin index. It has turned out that for some products with low glycemic index, a significant stimulation of insulin secretion has been observed! Not many people know that not only carbohydrate products contribute to fluctuations in blood insulin levels. According to the general thinking, if we took into account a carbohydrate-free product, the GI value would be 0. As the definition says, the glycemic index determines the increase in blood sugar after consuming 50g of carbohydrates, hence the protein or fat product will not raise the sugar level because there are no carbohydrates. And yet, it has been proven that after consuming a carbohydrate-free product, an insulin level in the blood can also rise. Consequently, an indicator has been developed showing the real level of insulin release after consuming a product. This indicator is called the insulin index.

It is usually the case that with the increase in blood sugar, the insulin level increases, but there are exceptions. A good example of the divergence of these indicators are dairy products. Milk, cheese, yoghurts according to the glycemic index table, have a low GI value, but they cause an elevated level of insulin in the blood.

Cambridge University Press (2005) published a study in which milk was compared in respect of glycemic index and insulin index. It was noted that the GI for milk was low i.e. 41 (0-100), while the insulin index was very high i.e. 148! For better understanding – IS for white bread is 100, while IS for eggs is only 31, so milk increased the level of insulin by 50% more than wheat flour!

This means that after the intake of milk, the blood sugar level rises slightly, in contrast to insulin, which reaches a very high concentration. I encourage you to read the table below, comparing the values of glycemic and insulin indices.

• Holt SH, Miller JC, Petocz P. An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods. Am J Clin Nutr. 1997
• Bao J. Atkinson F, Petocz P. Prediction of postprandial glycemia and insulinemia in lean, young, healthy adults: glycemic load compared with carbohydrate content alone. Am J Clin Nutr. 2011;
• Garrett Hoyt, Matthew S. Hickey and Loren Cordain* Department of Health and Exercise Science, Fort Collins, CO 80523, USA: Dissociation of the glycaemic and insulinaemic responses to whole and skimmed milk.