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Carbohydrates, blood sugar, and insulin: What is the link?

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Be it Muesli with fruit for breakfast, pasta at lunch, a light meal in the evening, or a piece of chocolate or chips as a snack in-between: We find carbohydrates everywhere. If you take a closer look at the topic of nutrition, and particularly at carbohydrates, sooner or later, you will come across terms such as “good” and “bad” carbohydrates. But which carbohydrates are “good” or “bad”, what foods contain them, and why is it so important to know the difference?

In the first part of the series on carbohydrates, we elaborated on the different qualities of carbohydrates. The chain length or complexity of carbohydrates play an important role. They affect blood sugar levels, satiety, energy supply, and the storage of body fat.

Beware of generalizations!

“Bad” carbohydrates, for example, usually refer to short-chained or “simple” carbohydrates. Sometimes whole foods are called “bad carbohydrates”. Fruits for example contain simple carbohydrates, but are far from “bad”. The contained carbohydrates are only one part of a fruit. Fruits contain many more nutrients, which, in turn, have a certain impact on your body. That is why macro-nutrients, especially carbohydrates, should always be considered in connection with the foodstuff and its overall composition, and vice versa, a foodstuff should not be condemned wholesale based on a single macro-nutrient.

What is the disadvantage of simple carbohydrates?

Simple carbohydrates reach the blood directly and quickly and are responsible for a steep rise in sugar – in the form of glucose – in the blood. For this reason, they are sometimes referred to as “fast” carbohydrates. Since too much sugar can be dangerous for several different systems of the body, it reacts with the distribution of large amounts of insulin, which cleans up the sugar from the blood. In turn, the rapid reduction in blood sugar level may lead to fatigue, weakness, difficulty concentrating, and an increased feeling of hunger.

High levels of sugar in the blood quickly saturate cells and excess glucose is transported to the liver, where it is increasingly converted into fat. Also, large amounts of glucose affect the processing of other nutrients, since the processing of carbohydrates is always of top priority for the body.

And what about complex carbohydrates?

Complex – colloquially known as ‘slow’ – carbohydrates, however, take much longer to reach the bloodstream, because their decomposition requires some more energy and time, resulting in the blood glucose level rising much more slowly and evenly. The consequences are a less explosive secretion of insulin and a long-lasting energy supply.

Assessing Glycemic Index and Glycemic Load

The Glycemic Index (GI) and the Glycemic Load (GL) units were introduced to predict the effect of a foodstuff on the blood sugar level.

Foods with a high Glycemic Index can rapidly increase our blood sugar level, whereas foods with a lower Glycemic Index cause a steady rise. Thus, the index refers to the aforementioned differences in the structure of carbohydrates. That’s the theory. A watermelon and a loaf of white bread – both evaluated based on the Glycemic Index – show the same values. Also, there are different views of what is regarded as “high” or “low”.

Since the Glycemic Index as a single point of reference may be misleading, the Glycemic Load is used as well. The Glycemic Load – in addition to the Glycemic Index – refers to the actual content of carbohydrates. As mentioned above, based on the Glycemic Index, a water melon and a loaf of white bread show roughly the same values. Based on a quantity of 100 grams, however, watermelon contains far fewer carbohydrates than white bread. Therefore significantly larger quantities of watermelon must be consumed to cause a corresponding increase in blood sugar level.

To evaluate the effect of the blood sugar level of a foodstuff, the Glycemic Index can only in conjunction with the Glycemic Load be a reliable value, as the latter set the food items mentioned above and the carbohydrates they contain in a corresponding ratio and considers also other specific factors, such as dietary fiber. These two values are therefore also used in many diets and in the diet of diabetics.

What is the role of dietary fiber?

Some foods such as potatoes are often simply referred to as carbohydrates. Foodstuffs, however, are not just equal to a kind of macro-nutrient but contain a mix of macro-nutrients, where a nutrient can have a significantly larger share – not to mention that they also contain micro-nutrients as well as fiber. Fiber is a special type of carbohydrate that cannot be processed by the body. It has a regulating effect on the blood sugar level, because it complicates the digestion of usable carbohydrates.

What foods should I choose?

Good sources of complex carbohydrates and fiber are whole grains, legumes and many types of vegetables. They are digested slowly, thus providing a long-lasting and even supply of energy and causing the body to feel satiated longer.

Simple carbohydrates are found primarily in processed foods in the form of various sugars and white flour. The problem with the latter is that it contains no nutrients and is thus broken down in a very short time, driving the blood sugar level up similarly to eating ordinary sugar.

If you choose primarily unprocessed foods in your diet and complement every meal with a large portion of vegetables, you will exclude a large number of foods that may affect you adversely and you won’t need to worry about the Glycemic Index and the Glycemic Load. Nevertheless, when selecting your foods, it doesn’t hurt to keep these units periodically in the back of your mind – especially since the preparation, in particular the heating of food, influences these two values (increase). To provide you with energy and power for your training, the focus in our Nutrition Coach is therefore on unprocessed foods containing complex carbohydrates.