One important measure of the nutritional value of foods is the glycemic index. In general, it refers to the ability of carbohydrate-containing foods to raise a person’s blood sugar levels (Mayo Clinic, 2020). It is worth clarifying that carbohydrates are one of several important biological classes of substances that form the basis of food, along with proteins, fats, and vitamins. Carbohydrates are not represented by sugars alone, and often the whole multitude of them is referred to by the combined term sugars. Among the carbohydrates that humans eat are fructose, glucose, sucrose, galactose, starch, lactose, and other types of natural sugars. In the human body, carbohydrates have multiple functions, and one of the most important of them is energy; thus, carbohydrates, in particular glucose, are used in the body’s metabolic processes, which results in energy production to support life processes. Every time a person consumes a carbohydrate-containing product, complex polymer chains are broken down in his blood to glucose. In this sense, the glycemic index is commonly referred to as the relative value that shows how much the body’s blood glucose content increases after eating a particular product compared to pure glucose (Mayo Clinic, 2020). It is reported that the glycemic index is commonly classified into three levels depending on the intensity of the increase in glucose content, namely:
- Low: 1 to 55
- Medium: 56 to 69
- High: >69
Different foods have different glycemic index values and thus differentially affect the increase in blood glucose levels. For example, according to the NHRMC (2021), foods with a low glycemic index should include most fruits, non-starchy vegetables, meat, and fish. Hence, consumption of these foods will lead to a minimal increase in blood sugar concentrations in the short term. In contrast, consumption of sugary drinks, starchy vegetables, breads, cereals, and snacks will cause a maximum increase in glucose. Foods with a high glycemic index tend to contain more processed carbohydrates and added sugars that can cause health damage. In contrast, foods with a low glycemic index are absorbed by the body much more slowly, so they result in lower glucose concentrations. For almost all foods, there are standardized index values calculated experimentally. Precisely, the index is measured among people who do not have diabetes and therefore have healthy pancreatic hormone function (Esther, 2019). Respondents are asked to consume 50 g of pure glucose powder, after which blood is drawn for several hours to analyze the dynamics of carbohydrate levels regularly. After recovery, respondents consume 50 g of a tested sample, for which peak blood glucose concentration changes are also determined. The value of the maximum level for the sample to the maximum level for pure glucose is the mathematical description of the meaning of the glycemic index.
In the study of the glycemic index, fiber plays a significant role as another essential component of foods. Fiber is classified into two types, soluble and insoluble, depending on the behavior of the molecules in the digestive tract. In the body, soluble fiber is converted by enzymes and fluids into a gel-like substance that requires energy to break down, which is derived from the conversion of glucose in the blood (NHS, 2020). In other words, consuming foods rich in the soluble form of fiber lowers the relative glycemic index of other foods.
References
Esther, E. (2019). What is glycemic index? Eat Right.
Mayo Clinic. (2020). Glycemic index diet: What’s behind the claims. Mayo Clinic.
NHS. (2020). The effect of soluble fiber on the glycemic index. Fiber Choice.
NHRMC. (2021). Low glycemic meal planning [PDF document].