Once the grain was stone ground and reduced to large particles. Although then it was passed through a sieve, the latter was summary and the flour that resulted remained all in all rather coarse (black flour).

The so-called “white bread” era had such a GI that went from 60 to 65, a fairly reasonable value. Today, among the rare types of bread that correspond to this standard, there is the famous bread “Poilâne” (famous French bread with stone-ground flour). This type of bread is particularly interesting in that it is made exclusively with natural yeast, which contributes even more to reduce the #glycemicindex.
The bread of the people, meanwhile, was once done with a coarse flour which retained all the required components of the wheat grain, hence the name “bread.” Since the particles were coarse, which contained a high proportion of fiber and protein and, as if that were not enough, was made with the yeast, the Glycemic Index was even lower (35 to 45).

With the invention of the cylinder mill in 1870, the manufacture of white flour has spread, at first in the West, then in all countries of the world. This new technical means obviously considered, even if wrongly, a “progress” would translate into an impoverishment of the nutritional quality of the bread.
Since then, thanks to increasingly sophisticated equipment in the milling, flour are becoming more “pure”, in the technical sense of the term. Which translates, nutritionally speaking: less fiber, less protein and micronutrients (vitamins, minerals, essential fatty acids …) and more fine particles. This results in an increasingly high glycemic index in all foods to which this hyper refined flour is a major component.
The physico-chemical properties of the starches constantly evolve under the influence of water, the variations of temperature and time.
Each treatment Hydrothermal, industrial or culinary, food causes a transformation that gives the property and a specific digestibility.
The result is a specific intestinal absorption that results in a relative glycemic response and insulin.
The glycemic index of a food is the result of several parameters, of which it is absolutely necessary to account for our nutritional choices.
Some starches or starchy foods, although complex, are more hyperglycaemic simple sugars. ” This happens for example in the case of French fries (GI 95), which are most hyperglycaemic sugar (GI 70).

Michel Montignac, the first nutritionist in the world to have proposed the use of the concept of glycemic index in weight loss, some fifteen years now, has actually been shown in all its works as the result of eating habits of the past 50 years, It has led to a dramatic increase in the prevalence of obesity in the World.