What are Carbohydrates?


Carbohydrates (or carbs) are macronutrients, the elements from which the organism is able to obtain energy. Depending on the carbohydrate source, they will also provide other important substances called micronutrients, also known as vitamins and minerals. They may also provide fiber as well depending on the molecular structure.

All you need to know about carbs

Carbohydrates are formed by molecules called saccharides, their main unit is glucose or a monosaccharide; depending on the type, they may have a structure formed by a single molecule (glucose directly) or formed by several molecules, polysaccharides (several monosaccharides) or even chains of them.

When one of these last types of carbohydrates is consumed, our digestive system must reduce them to the molecular unit, which is glucose. It will then be transported through the bloodstream to be used as the main source of energy for the brain, muscles, and other tissues and cells.

Function of Carbohydrates

Their main function is to provide energy, that is, they are an energy source or substrate that provides support for certain activities, depending on the intensity and duration of these activities.

But their role does not end here, they also intervene in other processes and thanks to their properties they produce other benefits:

Energy supply and regulation of glucose in blood

Glucose is the form in which the carbohydrates provide energy to the body (glycolysis). Therefore, since we start off with a superior molecular structure made of glucose chains, it will first have to be broken down into the smaller units.

Performance carbs Regulating the levels of glucose is one of the numerous metabolic functions in which the liver is in involved. When we consume food, a signalling system is triggered that is in charge of detecting the increase in glucose levels in the blood which results in an insulin release. Insulin can bind to a multitude of cells that have the appropriate receptors and it will make the absorption of glucose possible in the liver as well as the glycogen synthesis.This action is performed by the digestive system and the enzymes from the liver. Blood glucose levels should remain stable constantly, due to its great importance for the cell function.


There is another hormone, glucagon, which is discharged in the bloodstream when the glucose levels are low. It inhibits the absorption of glucose by the cells and stimulates the use of hepatic glycogen to be poured in the bloodstream. On the other hand, glucagon also produces a physiological phenomenon called gluconeogenesis, which consists on the synthesis of glucose from certain amino acids.

The liver has a limited capacity to supply glucose, so that after a period of not more than 24 hours, it is necessary to use other glucose sources.

During fasting periods, the fatty acids are transported from the adipose tissue through the blood flow to the skeletal muscle which will begin to use them as substrate to obtain energy. However, our brain cannot use this resource, since the fatty acids cannot cross the blood-brain barrier. The next stage will be that the muscle tissue will supply amino acids that will be transported to the liver to produce new glucose (gluconeogenesis). If the fasting continues for more than a day, the body can enter a state called ketosis, which is motivated by a lack of glucose, and the need for the body to “keep on working”.

Avoid Ketosis

Although the body can find other ways to obtain glucose, or work with another type of “fuel” instead, like in the case of ketosis (where ketones are used), it is not very advisable, specially for athletes.

Moreover, a regular intake of carbohydrates will avoid the use of proteins in order to synthesize new glucose (reducing gluconeogenesis).

In regard to ketosis, our brain can adapt to the use of ketones as a source of energy, although it prefers glucose. We must consume a minimum of carbohydrates (approximately >50g) in order to guarantee the glucose supply and prevent ketosis. If we want to adapt to the use of ketones, the first symptom that we will suffer will be headaches.

Carbohydrates are not Essential

As we have just explained, carbohydrates are not necessary to stay alive, unlike proteins and fats which provide essential amino acids and essential fatty acids respectively. This is because the body has the proper mechanisms to produce glucose from other sources, such as proteins and fats.

However, the most advisable, and above all, efficient option to obtain glucose is from carbohydrates so that we can produce energy and store it.

Add flavor

This is a minor function. There are receptors in the tongue that detect the sweet taste and send a signal to the brain. Sweeteners can be classified in two types: nutritive or non-nutritive.

The first ones supply calories, which are metabolized and used as energy. Within this type we can distinguish: sucrose, glucose, fructose, high fructose corn syrup, and lactose (we will elaborate this point later on). On the other hand, non-nutritive sweeteners do not supply calories, but they do produce the same sensation in our brain. Some of them are saccharin, cyclamate, xanthan gum, sucralose, and acesulfame.

Fiber supply

Carbohydrates are a source of fiber from different elements: cellulose, hemicellulose, pectin, and mucilage. Fiber makes the elimination of waste products much easier, since dietary fiber is both non-digestible and attracts water, the stool will be bigger and softer, which will facilitate its evacuation (with less pressure). If there is a considerable amount of pressure this can lead to certain problems in the gut, such as diverticula, or hemorrhoids.

The consumption of fiber can prevent weight gain due to the relation between the space it occupies in the stomach and its low calorie supply, the consumption of a small amount of this type of carbohydrate will provide us with a greater sense of fullness and satiety.

Fiber reduces the Glycemic Index, GI, from food (a concept explained below) and the absorption of cholesterol.

Carbs are a source of energy

Insulin and Carbohydrates

Insulin is a hormone that enables the use of glucose by the body. It is secreted by the pancreas when the body detects the presence of glucose in the bloodstream, and it will either store it or use it as energy. Insulin helps to maintain the sugar levels in blood stable, which avoids hyperglycemia (high glucose levels) after eating, and hypoglycemia (when there is a decrease of glucose levels), after physical activity, for example. Because of this, insulin helps to balance glucose in blood and keep it at the right levels. If the sugar levels increase, the pancreas will produce more insulin.

There are two concepts to relate insulin and the content and type of carbohydrates: the Glycemic Index and the Glycemic Load.

Glycemic Index

The Glycemic Index (GI) is a value assigned to food based on how fast it can increase glucose levels. In the GI food table, the higher the rate, the faster the release of glucose into the bloodstream will be. Therefore, the greater the stimulation of the pancreas will be, which will consequently increase insulin secretion.

On the other hand, food that has a lower GI, will offer more sustained energy properties, in contrast to those with high index, which can cause “an insulin peak”, which is a very sharp increase of this hormone, with a short energy use.

This is the classification of GI for food:

  • Low GI: <55
  • Medium IG: 56-69
  • High GI: >70

Glycemic Load

The other factor that is used to understand the physiological effect that the food with carbohydrates has on us, and which may be more complete, is the Glycemic Load (GL) because it addresses several features: it will take into account the GI, and the grams of carbohydrates per serving.

Like this, a food can have a high GI, and a low GL, that is, it does not have a high amount of carbohydrates that can produce a drastic increase of insulin.

To calculate the GL:

  • GL = (GI x grams of carbohydrates) / 100

The GL table will be classified as:

  • Low GL: <10
  • Medium GL: 11-19
  • High GL: >20

Remarks on GI and GL

The two concepts are relevant when it comes to eating food that exclusively contains carbohydrates, since the presence of other macronutrients, such as proteins and fats, can alter their response.

The conclusions that are drawn from the two concepts is that both of them are necessary to know how we are affected by carbohydrates, so that we can use them for our own benefits in the sport field. With regard to GL, despite having a low value, we can increase it if we consume a higher amount of said food.

Types of Carbohydrates

There are 2 types of carbohydrates: simple and complex. The difference between the two lies on their molecular structure and how fast they are absorbed and digested. Simple ones will be treated much faster than complex ones.

Simple Carbohydrates

They have a simple structure, formed by a single molecule, whose simplest form is glucose. They are known as simple sugars or monosaccharides. The word monosaccharide means “mono” one, and “saccharide” sugar.

Due to its molecular structure the body can process them very quickly, from which we obtain a brief energy response, which ends with a descent that coincides with the end of its use. The term “sugar” as such is a name given to a group of these carbohydrates which have a short chain, cyclic structure, and with the characteristic sweet taste.

Lack of Carbs

Within this group we can find several types:

Types of Sugars or Monosaccharides

  • Glucose: The main sugar that our body metabolizes for energy.
  • Fructose: The sugar from fruit. It is the sweetest and most water-soluble of all sugars.
  • Galactose: Normally found in large quantities in nature, it also combines with glucose to form milk lactose. It is usually found in legumes. After being absorbed by the body, galactose is transformed  into glucose in the liver. It is much less sweet than glucose or fructose.

Most of the sugars that we consume are disaccharides, because they are a mixture of two of the above monosaccharides. The properties of sweetness, absorption speed, and how they affect our body depends on which sugars are combined.

In this way, we will be able to find the following types:

Types of Disaccharides

  • Sucrose: Also known as table sugar, is formed by a combination of glucose and fructose. Although sucrose can be found in plants, only cane sugar, which grows in tropical climates, and sugar beet, which grows in colder regions, have enough amounts to make its extraction viable.
  • Inverted Sugar: It is similar to sucrose, but while the glucose and fructose molecules are bound together in sucrose, they are free in the case of inverted sugar. That is why its taste is sweeter than that of sucrose.
  • Lactose: The sugar in milk. It is a type of disaccharide formed by a combination of glucose and galactose. The molecular binding they form is called the beta-glucosidic bond, which can be difficult to digest for some people, and therefore it may cause stomach problems to many people with lactose intolerance.
  • Maltose: Maltose is found mainly in germinating grain, particularly barley, and it is less sweet than glucose, fructose, or sucrose. It consists on two molecules of glucose.

Complex Carbohydrates

They are polysaccharides, that is, they are made of a large number of glucose units. For this reason, they allow the storage of large amounts of glycogen. Starch is the main form of carbohydrate storage in plants, and we can find it in grains, seeds, and root vegetables.

Starches are a key part of the diet. About 50% of our carbohydrate intake comes from there. The main sources of starch are potatoes, beans, bread, pasta, rice, and other bread products.

Two types of starch

Starch can be divided in two types: amylose and amylopectin, each one with different properties. Amylopectin makes up about an 80% of the starch. Amylose has a colloidal structure in suspension while amylopectin is insoluble in water. While amylose is a straight chain polymer, amylopectin is highly branched.

Glycogen is stored in the liver and muscle. Although glycogen is structurally similar to amylopectin since they are both polysaccharides, the former has more branches and they are also shorter. Amylopectin can form stable starch gels that are capable of retaining water, while amylose is unable to do so.

After explaining both types of carbohydrates, depending on the physical activity, and especially its duration, we can benefit from one or the other.

Benefits of Carbohydrates for Sports

All the energy we need for life is provided by the food and liquids we eat. These nutrients are acquired from carbohydrates, fats, and proteins. Each of these categories is related to a certain health function, and in general terms, we should try to consume all of these food sources. Although the ratio and proportion of each one should be measured according to individual needs.

This time we are going to focus on the role of carbohydrates in sports and the benefits they provide.

More efficient energy source

This macronutrient is the most efficient energy source for athletes and sportspeople, no matter the type of discipline that is being performed, since they will provide energy for muscle contractions. When ingested, if they are complex, they must be digested and metabolized to the glucose unit, that is, to the monosaccharide structure, which will reach the cells to be used by them. If we ingest glucose directly, it can go to the reserves located in the liver and muscle, or be used directly as energy.

The form in which glucose is stored is called glycogen, so we can speak of hepatic and muscular glycogen. Glycogen will be present in any activity that exceeds an intensity threshold, especially if it is explosive and has a limited duration. In the case of longer activities the energy substrate will be a different one, like fat for example. However, there will always be an overlap of all substrates.


A proper supply of carbohydrates will help us to avoid using proteins as an energy source, which are not the most efficient way of obtaining energy. The function of proteins is to build and support the tissues that make up the body: muscle, bones, skin, hair…, so if we limit the consumption of carbohydrates, this will involve not having enough protein to carry out its own tasks. Also, if we want to produce glucose from proteins, it will cause extra stress to our kidneys and other systems involved, because this process produces metabolic waste products that must be excreted.

Energy from Carbohydrates

Each gram of carbohydrates provides 4kcals of energy. Additionally, they take water with them when they are stored, under 3g approximately. This means that if we consume carbohydrates once we finish our workout, our weight may increase, but it will be due to the fact that the storage of glycogen is retaining water in the muscle tissue.

Glycogen is a limited energy source, which means that the body has a limited deposit. Certain activities that are very intense and long can lead to the expenditure of glycogen. At these moments it is imperative to restore them or else we will not be able to carry on with the activity or we will not perform at desired levels.

In this context, it is common to find the expression “the wall” which means that the athlete has used up, or almost emptied his or her glycogen deposits, which forces them to cease the activity.

Carbohydrate Loading

Athletes and sportspeople resort to the “carbohydrate loading” strategy, which consists on loading the reserves to their maximum, before a planned glycogen expenditure  that is going to happen in a sports event, for example. In this situation, the carbohydrate intake is increased in much higher proportions than in a conventional diet. To facilitate this task, we use carbohydrate supplementation.

Carbohydrates during the workout

As we have previously mentioned, the carbohydrates deposits are limited and despite a carbohydrate load, we might need to restore this energy during the event depending on how long it lasts.

In these circumstances, carbohydrate supplements are the most efficient and optimal way to continue with the intensity of the activity.

Carbohydrate Supplements

We have described the fundamental aspects of Carbohydrates, and above all, their influence in the field of sports. Now, we will go on to list and explain what kind of carbohydrates we can find as sport nutritional supplements, why they are beneficial, and when and how to use them.

Carbohydrates Shake

Carbohydrates for our Daily Diet

This section shows the types that we would no include in the field of sports, carbohydrates used in food recipes, since their purpose is different. As we have seen in the description, this type of products are related to maintaining health:

Oat Flour

Oat flour is a ready-to-use flour obtained from oats. It provides a low GI, therefore, the release of glucose into the blood will be carried out slowly and progressively, and the glycogen load will increase gradually. The ideal moments to consume it would be for breakfast, or with the meal before our workout. It has a great versatility and range of recipes: protein shakes, pancakes or biscuits…

Rice flour

Rice flour has a similar function to the previous product, but its GI is higher, so it would be beneficial to use it before or after training. It also offers the possibility of being used as an ingredient to make recipes or mixed with protein shakes.


Fiber favors the digestive process, the intestinal tract movement, helps to fight certain diseases, and it is also needed to perform certain tasks.


Sucralose is a non-caloric sweetener that can be used to sweeten any recipe.

Xanthan gum

Xanthan gum is a type of polysaccharide that is used for certain recipes because of its thickening properties.

Carbohydrates for Sport Nutrition

In this section, we will list the different supplements focused on the peri-workout (explained below), which are a valuable resource for athletes. They will achieve certain improvements for the physical performance, such as:

  • Effective energy supply
  • Allowing to maintain the intensity of the activity
  • Prolong the activity
  • Facilitate recovery

What is the Peri-workout?

The Peri-workout is the period of time that encompasses the moments before, during, and after physical activity. It is a temporary line that we can set according to when we will perform our workout. Thus, we can place the Peri-workout in the morning, noon, or afternoon.

We can distinguish two types, depending on the time we have before the physical activity:

  • Outside the Periworkout
  • During the Peri-workout

The meals that are outside of these times, and according to our diet, should have Complex Carbohydrates.


Palatinose is a type of carbohydrate obtained from sugar, but with the peculiarity that, unlike sugar, it has a low GI. This will allow us to administer a sustained energy supply. It is ideal to combine it with other supplements with a higher GI because it will generate an energy backup if we are going to perform a long activity. Therefore, it can be consumed within the Peri-workout. Otherwise, if our goal is carbohydrate loading, it can be eaten at any other time of the day.


Amylopectin provides a series of characteristics that can be used as a carbohydrates-drink for training:

  • High molecular weight, which will help to generate an optimal recharge of the glycogen deposits, thanks to the easy energetic availability provided by the glucose units
  • Low osmolarity, which will provide a rapid transit and gastric emptying

Amylopectin has a high GI, however, it will facilitate an efficient recharge of the glycogen deposits due to its properties.

Carbohydrates Gel


Cyclodextrins are an enzymatically modified type of amylopectin to get a superior product. It is the best type of carbohydrate available for sport because it provides a faster carbohydrate recharge, and without causing any stomach upset.


Maltodextrin is a type of polysaccharide carbohydrate, that provides a high GI, but due to its molecular structure (formed by glucose chains branches) it can maintain the energy supply in a sustained way, since the bonds must be broken before, in other words, it has to be broken down into the final glucose units.


Dextrose is a type of monosaccharide, which means that it will provide glucose directly. The benefits of dextrose are interesting if we are looking for a sharp increase in insulin, like after the workout, or in combination with a carbohydrate with a lower-response during the workout.


The gels are ready-to-drink carbohydrate formulas that are meant to be used during the workouts in order to provide a fast energy response. It should be noted that after this rise in glucose there may be a drop in blood glucose, which means that you may need to use another gel to stabilize the levels. It is usually advisable to use it in the intervals in a competition when the energy reserves are at minimum levels, or after a long period of time. They can also be used just before a maximum effort, such as a mountain pass climb, or a speed test.

Carbohydrates for the Pre-Workout

In this period we are looking for a supply that will provide energy throughout the entire workout. We must establish the amount of carbohydrates depending on the time of the day, the meals we have eaten, the grams of carbohydrates in these intakes… It is always better to produce a mild insulin response, to avoid any type of hypoglycemia.

The most appropriate carbohydrates supplements for this moment would be:

  • Cyclodextrins
  • Amylopectin

Carbohydrates for the Intra-Workout

Due to the circumstances of this moment, using supplementation is possibly the most viable choice: our body is immersed in the exercise, and the blood is distributed around the periphery of the body, which is why ingesting solid food could cause stomach discomfort.

The most recommended carbohydrate supplements for this moment would be:

  • Cyclodextrins
  • Amylopectin
  • Maltodextrin
  • Dextrose
  • Gels

Carbohydrates for the Post-Workout

At this moment, the best option is to use a high GI carbohydrate to favor the increase of insulin and to quickly supply glycogen. In such a case, any of these supplements could be perfectly combined, and can be used along with supplements of Protein Shakes, Amino Acids, and/or Creatine.

The most recommended carbohydrates supplements for this moment would be:

  • Cyclodextrins
  • Amylopectin
  • Maltodextrin
  • Dextrose
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