The concept of “fast sugars” is called into question because of the development of the food industry, the variety of consumer products available on the market. The point with Claire Tournebize, sports doctor and Dominique Dumas, dietician-nutritionist.
Definition: what is a fast sugar?
“Today, we no longer speak of “fast sugar or slow sugar”, but of “food matrix”, it is the structure of the food, its arrangement and its resistance to absorption by the food wall which will interest usr“, underline Claire Tournebize and Dominique Dumas in the preamble. All the natural foodsexcept fat and animal matter, contain carbohydratesin the form of free sugars combined with fiber (not absorbable). These carbohydrates can be simple: composed of short chains of glucose, fructose, galactose like those included in fruits, vegetables, fresh dairy products, as well as industrial foods containing synthetic sugar. They can be complex, composed of longer chains including other non-absorbable carbohydrates (fibers) as in whole grains, pulses… “A carbohydrate becomes fast when its absorption/digestion is facilitated by subjecting it to a treatment modifying its structure (culinary preparation or industrial processing)“, they note. In this concept, sugar says “quick” to the ability to rapidly raise blood sugar : this concept takes into account the nature of the sugar present in the food but also the quantity of sugar contained in the portion (glycemic load). A food will therefore tend to behave like a “quick sugar” depending on different parameters such as the mode of consumption: raw, cooked ; the mode of presentation: whole, in pieces, mixed ; the mode of preparation: addition of proteins, fats or not… the method of production (ultra-processed food consisting of an amalgam of food extracts and additives). The higher the glycemic index like that of apple juice, the faster this sugar will be absorbed through the digestive tract, and the blood sugar level will rise instantly.
What foods contain fast sugars?
The glycemic index for the same food can be modified.
The glycemic index makes it possible to list foods: the higher the glycemic index of a food, the faster it will raise blood sugar. “For example, apple juice will almost instantly raise blood sugar levels.“, they add. Foods that contain sugars fast are:
- juiced fruit,
- fruit jellies,
- jams,
- honey,
- sugar,
- mashed potatoes (flakes +++),
- certain fruits, rich in glucose: grapes, very ripe bananas,
- cooked tapioca,
- white bread.
This list of foods is not exhaustive: it is necessary to refer to the glycemic index, but also to bear in mind that the composition of the food ingested and its processing, in particular industrial, will also have an impact. Foods, stripped of their fibers, or for some very cooked, release sugars which can thus pass more freely through the wall of our digestive system, making these carbohydrates very quickly accessible. “For example, the whole apple has a low glycemic index: due to its composition of simple sugar associated with fiber, it will be more slowly digested than apple juice, devoid of fiber“. The glycemic index for the same food can therefore be modified. It should also be noted that the combination of fats and/or proteins with a sweet food will slow down absorption and therefore lower the glycemic index : a light food (therefore less fat) can then behave like a fast sugar!
| Examples | Glycemic index |
|---|---|
| Skimmed milk | 32 |
| 1/2 skimmed milk | 30 |
| Whole milk | 27 |
| Whole milk yogurt | 24 |
What are the differences with slow sugars?
“Foods made from carbohydrates will raise blood sugar much more slowly in the blood due in particular to their more difficult digestion“. Foods containing fibers will offer greater resistance to our enzymatic system (food digestion) before sugar extraction and absorption, thus slowing gastric emptying and glycemic rise.
The differences between slow sugars and quick sugars are therefore based on the sugar complexity, food composition and absorption.
When to eat fast sugars?
“We have very few blood sugar reserves (1 g/l) knowing that we have 5 to 6 liters of blood in the body, the equivalent of a piece of sugar passing through the blood. On the other hand, we have significant reserves of muscle sugar in the form of glycogen which will depend on the diet followed upstream“, they explain. We can therefore use fast sugars in different situations which are:
► During continuous physical activity (an endurance sport) when it is more than 1 hour and/or that the person has not anticipated the energy demand by eating enough carbohydrates (low-sugar diet): it will be necessary to compensate by ingesting fast sugars;
► After a sustained workout in order to restore muscle glycogen reserves: the “metabolic window“, this is the period when the body is eager to renew its glycogen and protein reserves, particularly in the 2 hours following intense exercise. It is recommended to consume carbohydrates and proteins (for example a fruit combined with a milk protein such as natural yoghurt). Fruit fructose is slower than an industrial sugar and is nutritionally more interesting: “when we absorb a fast sugar, insulin will rise to allow the storage of sugar in the body : a large spike in blood sugar will be observed after drinking a soda or consuming sugar. This insulin peak can cause a call for sugar, a reactive hypoglycemia and therefore have the opposite effect: hypoglycemia can cause discomfort. The sugar is too quickly absorbed by the cells. This is why it is recommended to take a fruit instead“, they insist;
► In a special case of resugar to correct hypoglycaemia (person imposing a strict diet, skipping meals, diabetic condition, etc.).
What are the effects of fast sugars?
Fast sugars go fprovide energy quickly available to the organization. We are not talking here about harmful effects of sugar on health long-term : “fast sugars absorbed in too large quantities will have effects on the metabolism: risk of diabetes, obesity… generally due to excessive consumption of industrial fast sugars“.
Should we eat fast sugars before sport?
Eat fast sugars in the context of a sports competition, accompanied in particular by significant stress, can be interesting. “In this case, we can advise you a waiting drink with particular sugars limiting the effect of hyperglycaemia (glucose-fructose association for example)”. A balanced breakfast 3 hours before the race, or a snack 1 hour 30 minutes before exercise (very ripe banana, compote, etc.) before will have a real impact. Thus, the glycemic load will be sufficient to be able to start the race. “There is no need to add more: on the contrary, the intake of a sugary food can induce a reactive hypoglycemia causing discomfort and fatigueand eventually weight gain due to the need for resugaring“. The food program will be different depending on the sport practiced, whether in leisure or in competition. nutritionists and dieticians sports nutritionists can accompany you and advise you in your food choices according to your objectives.
What is the maximum amount of fast sugars per day?
For active sedentary people, ANSES (National Food Safety Agency) has issued recommendations limiting to: 5% the energy portion from simple added sugars (sugar, honey, jam, etc.) i.e. 100 Kcal (25 g) per day ; 100 g at most ideally, adding the part given by the plants. For the sportsman carrying out more than 6 hours of training per week and whose needs are increased, this can be very variable and according to his objectives: the best thing is to get closer to an authorized professional in order to to balance the ration as well as possible according to needs.
Thanks to Claire Tournebize, sports doctor and Dominique Dumas, dietician, graduates in sports nutrition, secretaries of the French Society of Sports Nutrition (SFNS)