Slowly-digested sugars (slow sugars)/ Rapidly-digested sugars (fast sugars), a totally mistaken idea

For years carbohydrates have been classified in two categories:

  • Fast sugars or rapid-absorption carbohydrates
  • Slow sugars or slow-absorption carbohydrates.

This distinction was based on what was presumed to be the time taken for our bodies to assimilate these sugars. People believed that glucose, after the carbohydrate had been digested, was absorbed more or less rapidly depending on the complexity of the carbohydrate molecule.

Numerous studies carried out during the past 20 years have shown that this classification is absolutely false. It has been proven that it takes our intestine the same lapse of time, approximately half an hour, to absorb glucose regardless of the complexity of its molecule.

“Fast sugars” and “slow sugars”, a false distinction!

As of the distinction between “simple sugars” and “complex sugars”, nutritionists were convinced that “simple sugars” (fruit, honey, powdered sugar and sugar cubes …), made up of one or two molecules, were rapidly and easily digested. People were, in fact, convinced that, since they required little modification by our intestine, simple sugars were rapidly turned into glucose and quickly absorbed by our intestinal wall to be made available for our blood stream. They thus classified them as “rapid-absorption carbohydrates” or “fast sugars.”

Comparatively, it was assumed that our digestive enzymes took much longer to transform “complex sugars” (cereals, pulses, tubers, roots…) —whose starch molecule is made up of hundreds of glucose molecules— into individual glucose molecules. People thought that this took a long time and that the absorption of this glucose was a slow and gradual process. This is why “complex sugars” were called “slow-absorption carbs” or “slow sugars.”

This classification was in fact elaborated on purely theoretical bases. Needless to say, it would have been an excellent idea to verify if in fact this theory coincided with what really happened when these nutrients entered our bodies.

Decades after dietitians, the press and many others had been sustaining this theory any which way, researchers started wondering at the contradictions and decided to look into the facts. They questioned the assumption that complex sugars’ long starch chain took longer than simple sugars to be absorbed by our small intestine.
In fact, gastric drainage speed, which in effect varied from one carb to another, was being confused with the time lapse required for glucose to show up in our blood stream.

Studies carried out by Wahlqvist show that the time lapses for glycemia peaks to appear are nearly the same for all carbs regardless of whether their molecules are simple or complex.

Thus, as can be seen in the above curve, all carbs (regardless of the complexity of their molecules) eaten by themselves and on an empty stomach are absorbed in 25 to 30 minutes. This 5 minute difference is insignificant if we consider total digestion time which is approximately 3 hours.

This is why it is important to realize that the time that elapses between the moment that we ingest a carb and the moment the glycemia peak appears (when the maximal glucose is absorbed) is exactly the same for all carbs whether they are simple or complex.

This fact, which was discovered in the 1980s, has been the subject of numerous publications and articles. Just to quote some of those published in France, we could mention Doctors Jean-Pierre Ruasse, Dr. Nelly Danan and notably Professor Gérard Slama.

For the past 10 years, Professor Slama has struggled to share this finding with as many nutritionists and specialists as possible. Through his publications and conferences in nutrition conventions (Notably DIETECOM), he has called on nutritionists and other dietitians to stop using concepts which have no physiological foundation and only serve to confuse the issue.

People, however, do not seem to be willing to listen. Nutritionists, the food industry and the Medias still keep on referring to the outdated idea of “slow sugars” and “fast sugars.” People in the sports field seem even more bent on continuing to apply this concept, acting blindly upon it.

We cannot fail to see how this unscientific approach casts a shadow on the seriousness of the field of nutrition. Many of the people in the field are, in effect, unwilling to revise their approach and adapt to these findings, which they should already have been applying for quite a while now. This reluctance to accept scientific progress is what gives the public the impression that there is a great degree of improvisation in the matter of nutrition. In fact, the opposite is true, scientific knowledge is there for one and all, it is just a matter of putting to use.

Conclusion : carbohydrate classification according to the notion of slow / fast sugars is totally misleading. Professor Slama has clearly proven that this distinction does not correspond to physiological reality. For the past 20 years, this notion has been overturned by the concept of Glycemic Indexes which, by measuring carbs’ potential to increase blood sugar levels, allow people to foresee the possible effects of carb consumption on their metabolism and avoid negative impacts and risks.

Michel Montignac was the first nutritionist to apply the concept of Glycemic Indexes for people wanting to lose weight. He did so in the 1980s and it has been one of the basic principles behind the Montignac Method since then and it has widely proven its effectiveness.

For further information on the Glycemic Index Concept

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