Diet and Glycemic Index

(GI) is a parameter that, referring to food, meals or diet in general, evaluates its ability to increase blood sugar (amount of glucose in the blood).

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The function of the glycemic index would be to predict the short-term metabolic impact of energy nutrients, or of one or more foods, allowing to draw up a nutritional program that monitors glycemic fluctuations and their consequences for the body.

"In theory", all this would allow:

• decrease the "hunger crises" or the sense of weakness due to the reflex hypoglycemia;
• lowering chronic hyperglycemia in sick subjects (type 2 diabetes mellitus) and its consequences (such as protein glycation);
• facilitate weight loss (in overweight subjects, especially insulin resistant).

As we will see, however, that of the glycemic index is a less relevant parameter than one might believe, even if the logic supporting a "possible therapeutic utility would seem to be flawless (apparently).

Let's go into detail.

, increases and then decreases blood sugar*>>.

* Blood glucose concentration measurable in mg / dL or mmol / L.

This index is expressed as a percentage (%), which refers to a specific test food, to which a value of 100% is attributed.

The measurement is done by feeding a portion of a food containing the same amount of carbohydrates as the test - therefore, not the same portion as the test.

There are two distinct equations, both available in the literature, different from each other because they are based on different test foods.

The most used one uses a solution of water and 50 g of glucose as a comparison parameter. The other instead, 50 g of white bread.

Since glucose in solution is 1.37 times faster than white bread, to obtain the conversion from one index to the other it is sufficient to multiply or divide the value of the second or first scale by 1.37.

The "glycemic trend, which graphically would draw a bell curve, is observed for a period of time equal to 120" (2 hours).

For example, a food with a glycemic index of 10 (%) is capable of increasing blood sugar at a rate equal to 1/10 compared to the glucose solution.

According to the logic of the glycemic index, foods can be divided into 4 categories:

• A very low GI up to 40;
• Low GI from 41 to 55;
• Medium GI between 56 and 69;
• High> 70.

"- exocrine secretions (saliva, pancreas), motility of the digestive tract, state of the mucosa, enzyme density, absorption capacity, etc.

Even the metabolic state in acute can give very flexible values. First of all, the same subject who is tested several times, even allowing glycemic normalization, before and after offers different numbers between them. This, of course, respecting identical procedural crimes. This is due to subtle extra- and intracellular mechanisms of "sensitivity" which, deducibly, require a longer time to normalize than the glycaemia.

Regarding the metabolic set in acute, there is "it must be said that the" glycemic trend - remember having a "2-hour observation - of a subject" emptied "of his muscle and hepatic glycogen reserves, with a high post-workout oxygen debt. , which participates in opening a "wide metabolic window, is completely different when observed under conditions of general homeostasis.

Discussing instead of metabolism in the chronic, the same subject with a different body composition (perhaps observed at different times of life) will give inconsistent results. When sedentary and overweight (probably insulin resistant), vice versa normal weight, muscular and active, the subject will have a totally different metabolic management of glucose.

Nutritional problems of the glycemic index

The glycemic index is influenced by the overall nutritional composition of the food or meal.

In fact, if a test such as the glucose water solution disregards any other aspect of composition, it is not so simple for foods.

• Fibers, fats and proteins reduce the glycemic index;
• The ripening of the fruits increases the glycemic index;
• Type of carbohydrate in question; glucose has the highest glycemic index, while fructose the lowest. Raw starch (polysaccharide) is indigestible and all starches have a different structure, with different glycemic indexes. Resistant starch has a very low glycemic index;
• State of hydration, since "dry" carbohydrates are not very digestible, hydrating them increases the glycemic index. Too much, however, can have the opposite effect;
• The cooking of carbohydrates hydrolyzes them, making them more easily digestible and quickly absorbed, increasing the glycemic index. However, if the composition is mixed, there may be factors that reduce protein digestibility, glycation, etc .;
• Cooking the fibers makes them more soluble, therefore less indigestible but more capable of gelling the digestive content. The impact is controversial.

For further information: Glycemic Index: What is it? Depends on what? For further information: Low Glycemic Index For further information: Low Glycemic Index Foods , in particular of glucose or short polymers of the same - such as maltodextrins.

On the other hand, it decreases if the meal also contains a lot of fat, protein, fiber, too much or too little water. Among sugars, fructose and galactose have a lower glycemic index - the same goes for their digestible polymers - since they must first be converted by the liver into glucose.

Paradoxically, a very large meal can have a lower glycemic index than a medium-small one.

But how could this be an advantage? It is not. This makes us understand the nonsense of taking the glycemic index as a reference when what really matters is the caloric amount of the diet - given by the glycemic load of all meals, but also by the amount of protein and fat. The metabolic impact, on the other hand, referring above all to the release of insulin (index and insulin load), deserves a separate discussion and will not be dealt with in this short article.

The glycemic index increases with deep cooking, although parallel factors such as water absorption, protein glycation, etc. may take over. It is lower, however, in the case of starch, if it remains raw or if it undergoes inversion (starch resistant).

Attention! The factors that increase or decrease the glycemic index must be appropriately contextualized, in the sense that even if they have an impact, they may not do so in a significant or decisive way.

reserve) in the liver and muscles;

Depresses the consumption of fats (lipolysis) and neoglucogenetic amino acids (neoglucogenesis);

It promotes liposynthesis (synthesis of fatty acids and triglycerides) starting from the excess of carbohydrates and dietary proteins, and the deposition of fats in the adipose tissue;

In conditions of muscle fatigue, it promotes the regeneration of damaged fibers;

It inhibits the action of glucagon;

It stimulates the secretion of leptin by the adipose tissue - which promotes the feeling of satiety.

Regardless of the glycemic index, what drastically increases blood sugar and insulin is the excess of carbohydrates, therefore of glycemic load.

In addition, AIG carbohydrates can find a very useful use in sports. For example, after a very intense and prolonged activity, which favors the depletion of glycogen stores, the body needs a certain amount of carbohydrates to restore (replenish) muscle and liver reserves. High glycemic index carbohydrates are especially helpful in replenishing these supplies as efficiently and quickly as possible.

Foods with High Glycemic Index and High Caloric Density Foods with Medium and High Glycemic Index Foods with a Low Clicemic Index Sugar White bread All fruit and vegetables (excluding exceptions) Certain refined grains (puffed rice, bag fries, wafers, cornflakes) Cookies Milk and yogurt Sweets and cakes Potatoes Fructose Sweetened drinks (carbonated drinks, "summer" drinks, iced tea, etc.) Croissant Whole grains (especially oats and barley) Foods containing "sugar" or "glucose syrup" in the ingredients Raisins Pasta cooked al dente   Certain types of fruit and vegetables (carrot, melon, pumpkin, etc.)   consequently, the evaluation of the GI has the purpose of understanding and evaluating which foods can be considered "recommendable" and which ones are not.

On the other hand, it is now known that blood sugar "spikes" more, rather than in response to the intake of high GI foods, after consuming a high glycemic load (CG). This "other parameter corresponds to the quantity of glucose that a food, in a standard portion, is capable of pouring into the plasma - an aspect which, not surprisingly, is also related to the caloric density of the product.

C "it must also be said that the glycemic load should be evaluated as a whole; moreover, what matters, on balance, are the total calories.

While considering the daily distribution of energy into several meals (for various reasons), absurdly, if our daily requirement were 2000 kcal and we only took 1800 kcal with a single meal, we would lose more weight than by making 5 the sum of which reaches a total of 2000 kcal.

Also on the glycemic load of the single meal, there would be a separate chapter to open. Will it really be wrong to drastically increase or decrease that of a single meal? It depends, above all, on what has been done before and what will be done after this meal.

In fact, if we were talking about unhealthy people, therefore insulin resistant and obese, we could say that it is always advisable to moderate the glycemic and insulin index (when possible of course), giving priority to the glycemic load and total calories.

Conversely, considering an endurance athlete, we could also find it profitable to create a maxi-glycemic load to be administered immediately after the performance, or even add up the entire carbohydrate quota by spreading it over the 2 hours of pre-intra- and post-workout.

It's not over. Thanks to the neoglucogenesis process, even foods containing mainly proteins (neoglucogenic amino acids) and triglycerides (glycerol) are able to increase blood sugar.

Furthermore, amino acids and fatty acids also have insulin stimulating properties. This means that not only carbohydrate-rich foods, but also others, can increase insulin, both in a glycemic-dependent and independent manner. .

- Powell K, Holt SH, Brand-Miller JC. HumanNutrition Unit, School of Molecular and Microbial Biosciences, University of Sydney, NSW, Australia - Am J Clin Nutr. 2003 Apr; 77: 994) a new and updated glycemic index table was published.

The novelty of this publication was the introduction of the concept of variability. In fact, it was discovered that the glycemic index of a food can vary according to:

• Varieties (for example, different varieties of a fruit have different glycemic indexes)
• Degree of ripeness (an unripe fruit has a different glycemic index than a very ripe fruit)
• Geographical area of ​​production (e.g. an apple grown in Denmark or Italy)
• Method of production (for example the various "industrial" products)
• Fat and protein content (e.g. ice cream)
• Fiber content (e.g. real corn flakes, rich in fiber, vs. higher calorie corn flakes much more similar to biscuits)
• Preservation and drying
• Cooking method (for example boiling or baking varies the glycemic index)
• Duration of cooking (for example pasta al dente or slightly overcooked)
• Other ingredients of the recipe (pasta with pesto will have a different glycemic index than pasta with tomato sauce).

For further information: Table of the "Glycemic Index

Click on the image to view the GLYCEMIC INDEX TABLE.

, the insulin index (II) and the insulin load (CI) - which as we have said also concern foods without carbohydrates - to establish the most adequate portions of foods rich in carbohydrates such as pasta, bread and sweet fruit.

Preferring pasta to rice or potatoes unnecessarily restricts our possibilities of variation, pushing us towards orthorexia. Orthorexia is a real obsession with healthy eating, comparable to anorexia and bulimia with the difference that these two pathologies they are related to quantity, orthorexia to food quality.

Those who already follow a balanced diet, integrating the concept of glycemic index, would not add anything useful to their eating behavior. In fact, in a healthy diet, the breakdown of macronutrients is calculated as a percentage of the subject's caloric needs. A normal-calorie diet consisting of about 55-60% carbohydrates, 25-30% fats and the rest in proteins, appropriately distributed over the course of the day, does not require anything.

The concepts of glycemic index and glycemic load, related to the resulting insulin load and index, are particularly important in diseases such as type 2 diabetes mellitus and related complications, the consequent hypertriglyceridemia and obesity.

In fact, by compromising the functionality of LDL (cholesterol transport lipoproteins), chronic hyperglycemia increases cholesterolemia and promotes the atherosclerotic process - responsible for serious cardiovascular events. It can also damage nervous and ocular tissue.If that weren't enough, by decompensating insulin production and function, it promotes overweight, leads to impaired glucose tolerance due to insulin resistance, etc.

Common sense and good nutrition education remain the most useful precautions. Eating everything but in moderation is in fact an optimal system for keeping the glycemic index, the glycemic load, the insulin index and the insulin load of the diet under control.

Overweight and metabolic pathologies are not caused by occasional transgression, but by bad daily habits. A healthy person can indulge in a small dessert at the end of each meal as part of a healthy diet, as long as a neutral calorie balance is respected.

In any case, it would be an excellent precaution to reduce the use of sugar to sweeten drinks, limit the consumption of sugary drinks (caca cola, fruit juices and so on) by drinking more water. To this it is advisable to associate an appropriate protocol of physical motor activity, which it allows you to better control your weight and, above all, to optimize the metabolism of dietary carbohydrates.