Glycemic index

Athletes are tend to speak of ‘slow sugar’ or ‘quick sugar’ but it must be understood that these concepts mean nothing. Indeed, as I demonstrate with my article on maltodextrin, there may be some sugars which have high, medium or low glycemic index, but what do that mean?

What is glycemia?

Blood sugar is the rate of glucose (sugar) in the blood. It varies depending on the individual activity (sedentary, sports…), on their food (starches, vegetables, sandwich, fast food…), the effectiveness of insulin regulating blood sugar (it lowers blood sugar).

What is that glycemic index?

The glycemic index measures the ability of a carbohydrate to raise blood sugar levels after a meal compared to a standard reference which is pure glucose. For the same meal in pure carbohydrate load, each food has a different elevation of blood sugar.

The glycemic index is calculated by considering the curve of glucose during the two hours after the absorption of the analyzed food and by making the calculation of the area under this curve, called « integral under the curve ». This surface will be compared with that obtained in pure glucose absorption, which represents the reference with a GI of 100. For example, a food that has a glycemic index equivalent to 50 has an integral under the curve twice less than that of glucose. The glycemic index is greater that the tested CARB-induced Hyperglycemia is strong.

The glycemic index measures the speed of absorption of carbohydrates and is used to measure the effect of a particular food. The more food increases blood sugar, the higher the glycemic index is. Thus, food with a high GI causes a rise in blood sugar quickly, in contrast to those having a low IG, where the climb is more progressive and the peak is lower. In no case we’ll talk « slow sugars » and « sugars » which are biased concepts: for example, current baguette type bread which is considered to be a ‘slow sugar’ has a high GI and fructose taken as a ‘quick sugar’ has a low GI. You guys follow me?

I recommend to limit food with high glycemic index between meals (see the list below).

Also the « quality » of the intake of carbohydrates has to be optimal. A varied diet brings complex carbs (legumes, cereals…) which will begin to be digested as they enter the mouth to the site of their assimilation in the form of simple carbohydrates, the intestine. The rise in blood sugar level shows the level of absorption of glucose and the digestibility of an individual complex carbohydrate (starch, maltodextrin…).

The main factors acting with the Glycemic Index:

Cooking

The more a food is cooked, the higher its glycemic index will be compared to its raw state.

The fat, protein and fiber content

This data of a food slows down the process of hydrolyzed and overall decreases the GI. A refined starchy food (white bread) has a glycemic index higher than wholemeal bread (rich in fiber ), (rich in lipids ) fried potatoes have a GI lower than potatoes to the oven or steamed. It is the case for leguminous plants (beans, lentils, peas…) which generally have a low glycemic index due to their richness in fiber and proteins.

The Texture

It acts on the Glycemic Index. The more an aliment is cut, chopped (etc.), the more its GI increases because it reates a better digestibility. A lentil soup causes a spike in blood sugar much more important than a lentil salad.

The aging

It increases the IG. This is the case when switching from green bananas to ripe bananas, new potatoes to stored potatoes.

For the athletes

It is recommended during the year to keep a diet with food with low to medium Glycemic Index, as well as before the effort. Focus during and after the effort on an alimentation with a medium to high potential glycemia, using in parallel:

Before the effort

I recommend a drink rich in carbohydrates and especially in fructose. Indeed, as explained previously, the fructose has a low GI which means that sugar is consumed « in offbeat. » To sum up, it will be used by the body potentially during exercise. Moreover, this allows to avoid hypoglycemia during the effort that would be caused by an intake of carbohydrates with high GI. Small reminder on the malto, this drink is not a slow sugar as some brands claim! Here is the demonstration with my article on maltodextrin .

During the exercise

Your sports drink should contain glucose, fructose and maltodextrin. The ideal is to have glucose in majority because it is directly assimilated by the body but beware, there is a difference between having the main part and having just that! Carbohydrates variety is still the best form of contribution!

After the exercise

Choose a recovery drink with a low glycemic index including carbohydrates (glucose, fructose, maltodextrin), (plant preference) proteins and lipids (omega 3 type).

Some foods according to their Glycemic Index rankings

Low GI foods (GI < 55)

0% yogurt, fructose, grapefruit, whole milk, dried apple, cooked green lentils, raw carrots, dried apricots, soy milk, skim milk, cooked split peas, cooked chickpeas, sweetened 0% yogurt, pear, apple, Plum, apple juice with no added sugar, cooked green peas, peaches, oranges, cooked pasta, cooked sweet potatoes, bread, whole grain, pineapple juice with no added sugar, grapefruit with no added sugar, brown rice, orange juice with no added sugar, Kiwi, boiled sweet potato, light cereals.

Medium GI (55 ≤ IG ≤ 69 ) foods

Banana, natural fruit Cocktail, canned sweet corn, cooked semolina, Muesli, cooked Brown rice, fresh apricots, honey, syrup, cooked rice, cooked new potatoes, dried figs, apricots in syrup, dried grapes, rye, melon, saccharose, fresh pineapple, beer, croissant, polenta, wholemeal bread.

High GI (≥ 70 IG) foods

White bread, boiled potato, wholemeal bread, effort dietary drink (medium size), fries, beans, gummies candy, mashed potatoes, Corn flakes, cooked carrots, puffed rice, potatoes in the oven, gluten free bread, White baguette, Glucose, Maltose.

Conclusion

I always recommend meals or snacks including macronutrients protein, lipids, carbohydrates, fibers in balanced quantities and with a modified texture. Limit canned or « light in fat and sugars » food in order to limit the ingestion of additives (Conservatives, sweeteners, flavor enhancers, agent in charge…) detrimental to athletic performance and health of the athlete in general, when consumed regularly and in greater or lesser quantities. Thus, the more natural is a product, the more organoleptic qualities and micronutritionals are preserved (fibres, vitamins, minerals, trace elements).

Sportingly,

Nicolas AUBINEAU
Sports Dietitian Nutritionist