What is glycemic index?
The glycemic index is a measure to determine the effect of a carbohydrate-containing food on blood sugar levels. In some cases, the name GI is used for this purpose or the abbreviation GI (symbol NCI or nGlyx). The higher the value, the higher the blood sugar levels.
A similar parameter is the insulin index, which indicates the direct impact on insulin levels instead of carbohydrates.
The concept of the glycemic index was introduced in the 1980s as part of the diabetes research. Thus it was found that about white bread can raise blood sugar after eating more than table sugar. But the difference could not be explained by the structure of carbohydrates (ie, complex or small molecule).
Meanwhile, there are several diets that attach to the GI meaning, for example, the Montignac Method, the Low-glycemic diet and the Logi method.
Recent research results have shown that the glycemic index, for example, plays only a minor role in weight gain and is individually very variable.
Determination
The glycemic index is in numbers to the blood sugar-increasing effect of carbohydrates or foods. The blood glucose-increasing effect of glucose serves as a reference value (100). It so much dextrose or as much of the test food is eaten from a subject that each 50 g carbohydrates are contained in the consumed portion. The picture shows the change in blood sugar is shown as a black line (here a simplification!). The glycemic index is (mathematically the integral) defined by the ratio of the areas under the curve of blood glucose levels during the first two hours after meals consumption.
A GI of 50 indicates that the integrated over time blood sugar increase the assessed food only accounts for half of the increase in glucose, in this case the yellow area is half the size of the red area.
Carbohydrate foods that cause a rapid and high blood sugar levels, but not necessarily have a high glycemic index. If the blood sugar levels namely after the fast, high rise rapidly again, the index may be low despite the short-term high blood sugar levels. And food, according to their pleasure, the blood sugar level increases slightly or slowly, do not necessarily have a low glycemic index. Does the small increase that is long on, the index may still be high. For a reliable statement about the effect of a food on blood sugar levels of a person therefore the blood sugar level chart is decisive and far more meaningful than the index.
Caution is advised in search of GI values about on the internet. Especially in America are tables in circulation, put the GI in relation to white bread, which then has a GI of 100. The values can, however, convert into each other by a factor of 0.7.
At what value of GI is to be regarded as high, are valued differently at different diets.
In general, the following classification is used:
-A high GI is greater than 70
-GI values are means from 50 to 70
-A low GI is less than 50th
This classification is applied, for example, in the Low-glycemic diet and Logi method.
Another classification uses the Montignac method. Here are foods with a GI value greater than 50 poor, between 35 and 50 well and in a GI value less than 35 very well.
Importance of GI for athletes
Main factor to influence the GI is the training condition. What food is eaten, is secondary.
The findings about the GI of foods contributed to a better understanding of the energy supply for during exercise. This knowledge is used by both endurance and strength athletes from. Studies have shown that an intake of foods with a high GI leads to a time of 30 to 60 minutes before exposure to premature fatigue. It then comes namely after an insulin spike right at the beginning of the load to a drop in glucose levels and an emptying of the Glykogenspeichers, and a rapid reduction of free fatty acids. Instead, strong carbohydrate-containing foods should be consumed with an average GI to ensure a steady supply of energy from carbohydrates, which is just by the absence of a high insulin level possible. It has also been found that taking a not overly large amount of high-GI carbs is low immediately after physical exertion, because this very quickly gets into the blood and also the absorption of calcium and magnesium ions in the intestine accelerated, leads to a very rapid replenishment of energy reserves. These are not meant for the next load, but the body will just be available during recovery.
Importance of GI for Obese
Foods with a high GI lead to a sharp increase in blood sugar levels, which then leads to a strong release of insulin. This in turn leads to an increase in the uptake of glucose into muscle and fat cells and also stimulates the storage of fat and carbohydrate in the form of storage of glycogen. Therefore, some authors assume that (low blood sugar) resulting as a consequence of consumption of foods with a high GI after about 2 to 4 hours a shortage of energy sources in the blood. This in turn actively eating such foods, which increase blood sugar quickly, and run for allegedly in a vicious cycle and eventually to obesity. In fact do not occur hypoglycaemia in healthy but because of the glycogen stores if necessary carbohydrates can be released again. There are conflicting studies on this theory.
In general, however, assumed that the sharp drop in blood sugar levels in foods with a high GI to changes in the digestive process, including a hunger and thereby leads to renewed food intake, switching to foods with lower GI and glycemic load (GL) appear in overweight effective represent a therapeutic measure. It is in addition to the impact on obesity, especially on the direct connection of GI with type 2 diabetes mellitus (adult onset diabetes) and cardiovascular diseases, especially in children and adolescents, pointed.
Criticism
-The GI was developed for research purposes as a laboratory parameters and is less practical for the everyday diet. Namely, it describes the blood glucose response to the supply of 50 g of carbohydrates, which are fed over a certain food, and not the reaction on 100 g of food.
For example, the GI of cooked carrots (carrots) is 70 (more recent studies give a lower value). Since carrots are very low in carbohydrates, 800 grams of carrots should be eaten so as to supply 50 g carbohydrates. Unlike in carbohydrate-rich foods: baguettes also has a GI of 70, but already low 104 g of which are sufficient to supply the required amount of 50 g carbohydrates. Based on the GI of 70 is the scientific statement thus: The ingestion of 104 g baguette bread leads to the same increase in blood sugar, such as the inclusion of 800 g carrots.
-An adaptation of the GI represents the so-called glycemic load (GL). It takes into account the respective GI and the carbohydrate content of each food, but not fat and protein.
-Additionally, the actual blood glucose response greatly depends on what foods are consumed at a meal together. The GI values of individual foods may not be simply added together, which leads to incorrect results.
-There is considerable individual variation: the same food does not cause in different persons the same rise in blood sugar levels. Even in the same person already different values have been measured in studies.
-The fat content of a food has little effect on blood sugar levels. It reduces the GI value therefore distinctly, but plays an important role for the calorie intake.
-With a reduction in carbohydrate intake will inevitably either eaten more protein or more fat.
-One also frequently mentioned criticism is that for the erection and dismantling of adipose tissue ultimately not the insulin levels, but only the energy balance is crucial. Thus the basic idea of a GI-restricted diet would be invalid: To troubleshoot preponderance of GI would indeed be irrelevant. This is also the position of the German Nutrition Society.
-The Consumer Advice Centre North Rhine-Westphalia said in a statement: "It is not scientifically justifiable to implement the concept of GI and, for example, the consumption of potatoes and (wholemeal) discourage cereal products with high GI and high GL. The influence on the reduction of obesity is controversial and have hardly been investigated systematically. "
In an intervention study of the pan-European Diogenes (Diet, Obesity and Genes) project, it was shown that a diet with a low glycemic index is no advantage in terms of (re) increase in body weight.
-Another point of criticism of the concept is that the GI changed significantly by the type of processing. Heating, cooking and crushing can increase the GI. Noodles, which were cooked just five minutes, have less influence on the response of the blood sugar as noodles (GI: 37), which were cooked 10-15 minutes (GI: 44) or even 20 minutes (GI: 61). Precise information on GI in processed products is thus hardly possible.