Insulin Index – What It Is and How to Use It

Insulin is a hormone secreted by the beta cells of the pancreas. One of its primary roles is to regulate blood glucose levels. No other hormone in the body exhibits the same effect. The pancreas releases insulin when blood glucose levels rise, causing an immediate increase in the hormone's concentration in the bloodstream after a meal. Insulin facilitates the transport of glucose to liver cells and muscle tissue. It also influences protein and fat metabolism, promoting fat storage and muscle protein synthesis. Additionally, insulin signals the brain about the body's energy status by inhibiting the activity of neurons responsible for food intake. There are two types of insulin secretion – basal and postprandial. Basal secretion remains consistently low, significantly lower than postprandial secretion. It follows a circadian rhythm, being higher in the morning than in the afternoon or at night.

Insulin is crucial for regulating blood glucose levels. For a long time, it was assumed that foods causing significant blood glucose spikes would also trigger substantial insulin release, while those with minimal glucose impact would have no effect on insulin. However, this is not always the case, as high-fat and high-protein foods also influence insulin secretion. The first comprehensive study on how meals affect insulin levels was conducted by S. H. Holt, J. C. Miller, and P. Petocz in 1997. Their research compared insulin responses after consuming portions of various foods providing 1000 kJ (approximately 239 kcal). The study included 38 products divided into six categories: fruits, confectionery, snacks, carbohydrate-rich foods, protein-rich foods, and breakfast cereals. White bread (FII 100%) served as the reference food. The findings revealed that protein-rich foods and sugary snacks with high fat content caused the most significant insulin release. Based on these results, the Food Insulin Index (FII) was developed to measure how a food affects insulin levels after consuming 1000 kJ of energy. Subsequent studies, including those by K. J. Bell and colleagues, demonstrated that meals with a low FII lead to reduced insulin secretion in both healthy individuals and type 2 diabetics, without altering blood glucose levels.

Currently, the insulin index has been established for 120 food items (J. Bao et al. 2009). Insulinogenic foods that trigger substantial insulin release with minimal blood glucose elevation include fruit yogurt, ice cream, potatoes, jelly, peanuts, chocolate bars, cooked rice, chips, and popcorn. A meta-analysis by A. Rietman et al. demonstrated that proteins exhibit insulinotropic properties, meaning they enhance insulin secretion. A high-protein diet lasting over six months (consuming protein exceeding 20% of daily caloric intake) may contribute to the development of type 2 diabetes mellitus. Particular attention should be given to amino acids such as arginine, alanine, and glutamine, which increase insulin secretion by over 200%. Conversely, fat promotes insulin secretion, but only in cases of a single, high intake of this macronutrient. Regular excessive fat consumption, however, suppresses insulin production. The table of the insulin and glycemic index of selected food products is based on research by S.H. Holt, J.C. Miller, and P. Petocz (1997) as well as A. Jeznach-Steinhagen et al. (2020).

The insulin index is one of the tools that can assist in dietary management for carbohydrate metabolism disorders, though its application remains limited due to insufficient knowledge. To date, it has only been established for a small selection of foods. Additionally, its interpretation is challenging because it is still unclear which insulin index values are considered low and which are high. Consequently, this parameter is not practically applicable. An increase in insulin levels in the body is directly linked to a rise in blood glucose levels. In cases of carbohydrate metabolism disorders, adhering to the principles of a diet with a low glycemic index and low glycemic load is sufficient, while also recognizing that proteins and large amounts of fats also stimulate insulin secretion.