Glycemic Index and Glycemic Load - How to Utilize Them in Your Diet Planning?

The Glycemic Index (GI) is a measure that indicates the speed at which blood glucose levels rise after consuming 50 grams of easily digestible carbohydrates (glucose) in products compared to the increase in blood glucose levels after consuming the same amount of carbohydrates in the form of pure glucose. It is a method of measuring the speed at which the carbohydrates in the product are converted into glucose circulating in the body. It is assumed that the intake of 50 grams of glucose in carbohydrate-containing products (glucose) leads to a 100% increase in blood glucose levels, which means that the glucose content of the product has a GI of 100. The higher the GI of a product, the faster it is digested and raises blood glucose levels, leading to a high insulin level secreted by the pancreas. As a result, the glucose level often drops to levels below the initial level, leading to a state of reactive hypoglycemia. Reactive hypoglycemia is a state in which the blood glucose level drops below 55 mg/dl within 4 hours after eating. It can manifest as weakness, fatigue, confusion, cramps, dizziness, and fainting. To prevent such a state from occurring, the diet should be based on products with low and medium GI. Products with low GI are absorbed much more slowly due to slow digestion, avoiding extreme fluctuations in glucose and insulin levels. Based on the speed of the postprandial increase in blood glucose levels, food products are divided into three groups: products with low GI ≤55, products with medium GI 56-69, and products with high GI ≥70. It is recommended to choose mainly products with low and medium GI. Products with high GI can occasionally appear in the diet in small amounts and are best combined with products with low GI.

Factors that contribute to reducing the glycemic index include: - a high ratio of amylose to amylopectin, e.g. in legumes such as lentils, chickpeas, peas, beans, and barley; - the content of fructose (present in fruit) and galactose; - a high content of β-glucan (found in cereal grains such as oats, spelt, wheat, and barley, as well as in mushrooms and bamboo); - cooling (cooked potatoes should be placed in the refrigerator to form resistant starch, which lowers the glycemic index of the product; in this way, prepared potatoes can be included in the diet, although they are not recommended for people with diabetes and insulin resistance); - low maturity, e.g. green bananas; - a high content of lectins and phytates (found in legumes, nuts, tomatoes, eggplants, and peppers); - a high content of proteins, fats, and organic acids; - low milling (rice has a lower glycemic index than rice flour). Fats and proteins delay gastric emptying, digestion, and absorption of carbohydrates in the small intestine, which affects the reduction of the glycemic index. In practice, it is advisable to combine a carbohydrate-containing product (e.g. oatmeal) with a protein-rich product (e.g. cottage cheese) and fat (e.g. nuts) to lower the glycemic index of the entire meal. Similarly, with bread, which is a product with a high glycemic index - to lower it, it is recommended to eat bread with cottage cheese (protein source) and fresh vegetables (fiber source), sprinkled with sunflower seeds (fat source). Soluble fiber delays or inhibits the release of the enzyme (amylase) that breaks down sugar, which also leads to a decrease in the glycemic index. Insoluble fiber has no effect on the digestion and absorption of carbohydrates. Products containing organic acids (e.g. lactic acid) have a lower glycemic index, hence fermented dairy products such as yogurt, kefir, and natural yogurt have a lower glycemic index than milk. Resistant starch can also lower the glycemic index - the more of it in a product, the better; also because it is a food source for bacteria of the genus Lactobacillus and Bifidobacterium, which have a positive effect on the gut flora. To increase the amount of resistant starch in the diet, starchy products should be prepared at high temperature without water or with little water (baking or steaming) and served cold, with cold water poured over them.

The factors that increase the GI are: - low amylose-to-amylopectin ratios, e.g. in rice, potatoes and wheat flour; - high glucose content (either added during the production of the foodstuff or resulting from long storage of vegetables or fruits); - low β-glucan content; - roasting, extruding and cooking, such as corn, popcorn; - high maturity, e.g. ripe bananas and grapes; - low lectin and phytate content; - low protein, fat, and organic acid content; - fine grinding; - grain cleaning. Long cooking of starchy foods leads to a change in their structure. Under the influence of heat, bonds between starch molecules start to break and bind large amounts of water. The starch begins to swell and form a paste. The degree of paste formation depends on the amount of amylose in the product. The less amylose is contained, the faster the product is digested, which leads to a rapid increase in blood sugar levels. How can this knowledge be applied in practice? An example would be a porridge prepared in two different ways. The porridge made from quick-cooking oats and cooked for a long time in milk will have a higher glycemic index than the porridge made from coarse oats and topped with yogurt. There are several factors that increase the GI of the first porridge – the cooking, the fine grinding of the product, and the absence of organic acids. Long storage of root vegetables and tubers also increases their glycemic index – young potatoes will have a lower GI than those stored several months earlier.

When using the glycemic index, we do not take into account the amount of carbohydrates consumed in a given product, but only their quality and the rate at which they are absorbed into the glucose. However, there is another parameter, called the glycemic load (GL), which takes into account both the quality and quantity of carbohydrates consumed. The glycemic load is calculated by multiplying the amount of carbohydrates available in a portion by the glycemic index of the product and then dividing the resulting value by 100. GL = (available carbohydrates in the portion [g] × GI) / 100. Based on this parameter, food can be divided into three groups: foods with low glycemic load, foods with medium glycemic load, and foods with high glycemic load. It is also important to consider the glycemic load of the entire daily diet, which is also divided into three groups: a diet with low glycemic load, a diet with medium glycemic load, and a diet with high glycemic load. An example that can speak for the consideration of the glycemic load is watermelon. Although watermelon has a high glycemic index, its content of carbohydrates is low, which results in a low glycemic load. However, the condition for this is to eat about 100-150g of the watermelon. In addition, it is also important to properly compose meals by combining foods with low glycemic index with foods with medium glycemic index. A diet with low glycemic index and low glycemic load can help reduce weight, normalize blood sugar and lipid profile, and reduce the risk of many civilization diseases.