The levels of glucose in the blood (glycaemia) are not constant, but follow a curvilinear trend; phases of growth alternate with others of decrease, depending on meals and their composition. The minimum values are reached on an empty stomach, for example in the morning before having breakfast, while the glycemic peak is maximum after about an "hour - an hour and a half" from meals, especially if they are rich in simple sugars.
The trend of glycemic levels after a meal is influenced by the quantity and quality of the food eaten. In figure 1, for example, it can be seen how the glycemic peak reached following the ingestion of a solution of 75 grams of glucose, arises long before a normal meal (figure 2), where carbohydrates (starches) must first be digested, then broken down into glucose.
In FIG.1 it is noted that too high glycemic peaks are characteristic of diabetes and of the stages of reduced glucocidic tolerance that precede it; to learn more about the clinical significance of the test, see the article OGTT: Oral glucose load test.
As anticipated, when the meal is mixed, the glycemic peak is reached approximately one "hour, one" hour and a half after ingestion; for adults, this peak should be less than 180 mg / dl (renal glucose threshold), even if the optimal values are below 140 mg / dl. In teenagers the glycemic peak is more consistent (<200 mg / dl), as well as in school-age children (<225 mg / dl) and in infancy (<250 mg / dl). These values also represent the reference parameters for diabetic patients on drug therapy.
In this last image we can see the difference in the entity and in the amplitude of the glycemic peak following the intake of foods with a high (left) and low (right) glycemic index (glycemic index GI). Glycemia rises very and rapidly when a meal is mainly composed of large quantities of simple carbohydrates (with a high glycemic index), while it gradually increases if the carbohydrates are complex and associated with proteins, fats and fibers (see concepts of index and load glycemic). Examples of foods with a high glycemic index are glucose, honey, white bread, potatoes, crackers, breakfast cereals, grapes, bananas, and polished rice. Those with a low glycemic index include yogurt, peas, apples, most of the vegetables, beans, nuts, parboiled rice and milk. The fundamental importance of avoiding too high glycemic peaks - through a "careful choice of foods - is illustrated in the" article dedicated to the relationship between blood sugar and weight loss.
