As explained in the previous nutrition post, our body uses carbohydrates as main fuel to generate energy during exercise. These carbohydrates are primarily stored in the muscles and liver in the form of a long glucose units’ chain, a compound called glycogen. After 90-120 minutes of intense exercise, the glycogen stored in the liver begins to deplete. In order to continue with the exercise and maintain performance, the ingestion of carbohydrate is necessary. This carbohydrate intake can be accomplished with food and/or with sport supplements. Energy gelsare among these supplements.

Energy gels are a concentrated source of carbohydrates, as 65–75 % of their composition is carbohydrates. Each individual gel provides about 30 g of carbohydrates and 80-120 kilocalories. The use of these gels is highly recommended in ultra-endurance events such as the ones organized by Transiberica® as an aid to cover the race carbohydrate needs. The advantages of this type of supplements are that they are easily transportable as well as easily ingested and digested. However, care must be taken with these type of products as they can cause gastrointestinal discomfort that could affect performance. It is really important to include the experimentation of different nutritional strategies and products as part of your training routing in order to find the products and protocols that best suits you. In this article an analyse of the different types of gels available on the market is going to be made in order to find the most suitable gel or gels for these events.

It worth noticing that, apart from the supply of carbohydrates, commercial gels are starting to incorporate other compounds with the aim to increase performance and/or delaying fatigue. A brief summary of the composition of the gels is shown below:

Diagram showing Summary of the general characteristics of energy gels
Figure 1 Summary of the general characteristics of energy gels

1. Types of carbohydrates

Carbohydrate content is the most important compound that we must take into account when choosing our gel. After all, the main objective of the gels will be to obtain energy and replenish the body’s glycogen. It can sometimes be difficult to decipher what type of carbohydrate the gels we consume contain. This can be due to the different nomenclatures used and because there is not a very strict regulation regarding “sugar” and “carbohydrates”. The term “sugar”, for example, is a generic term that it is used in the nutritional tables of products and encompasses a lot of different compounds such as glucose, maltose, fructose, sucrose…

Therefore, we must look at the list of ingredients, which is not easily decipherable either. Let’s see what kind of carbohydrates we can find:

Simple carbohydrates:

Glucose (also listed as dextrose) and fructose.

Chemical structure of glucose and fructose
Figure 2 Chemical structure of glucose and fructose

Complex carbohydrates:

Isomaltulose(glucose + fructose), dextrins(a chain of glucose units) and maltodextrins (a chain of glucose units). In fact, dextrines and maltodextrines encompass a group of compounds. Maltodextrin can be a combination of between 3-17 glucose units unit by its carbons 1-4. Dextrins are combinations of between 3-20 glucose units that can be linked by its carbons 1-4 or 1-6. The result of the different linkages is that maltodextrins will form lineal chains while dextrin will be able to form both lineal and branched chains.

Diagram showing Chemical structures of maltodextrin, isomaltulose, lineal dextrin and branched dextrin
Figure 3. Chemical structures of maltodextrin, isomaltulose, lineal dextrin and branched dextrin

Carbohydrates created using new technologies:

Thanks to recent research and new technologies, there are two new artificial types of carbohydrates on the market: highly cyclic dextrins or the so-called Cluster Dextrin® and hydrogels.

Cluster dextrin ® is artificially created by modifying amylopectin to obtain a more cyclic structure molecule. This molecule is made up of 60-70 glucose units.

Diagram showing Cluster Dextrin formation
Figure 4. Cluster Dextrin ® formation

Hydrogels are a gel-like solution normally composed by a mixture of maltodextrin and fructose to which sodium alginate or pectin is added. Sodium alginate and pectin turns the mixture to a gel at acidic pH, as when the mixture contacts the stomach acid. In the image below there is a summary of the process that in the body when ingesting a hydrogel:

Diagram showing Hydrogel behaviour in the body
Figure 5 Hydrogel behaviour in the body (1,2)

Non-purified carbohydrates:

Glucose syrup and cane sugar will be included in this group, since they are complex mixtures of different carbohydrates which exact composition is unknown.

The definition given in the regulation for glucose syrup is as follows: concentrated and purified aqueous solution of nutritive saccharides obtained from starch and/or inulin (3). As you can notice, the definition mentions saccharides which means carbohydrates in general. The law requires that this syrup has at least 20% glucose on dry weight and that the solid content is at least 70%. This is all the information we will have. So, we must assume that this syrup will have carbohydrates of different glucose units lengths, without knowing which exact compounds they are.

The definition for cane sugar is: partially purified sucrose (glucose + fructose), crystallized from partially purified cane juice without further purification, but not excluding centrifugation or dehydration, characterized by sucrose crystals covered with a film of cane molasses (3). Molasses is a complex mixture containing sucrose, inverted sugar, salts, and other alkali-soluble compounds. Therefore, cane sugar will be a mixture of carbohydrates with a glucose:fructose ratio of 1:1.

Conclusion 1:
we will preferably choose gels in which the carbohydrate mixture is clear and we can ensure that it will always be the same. For this we will avoid unpurified carbohydrates such as syrups and cane sugar.

2. Choosing the best type of carbohydrate for energy gels

It can be believed that the type of molecule ingested has not importance. After all, the body will break down all the above-mentioned molecules and absorb them in the intestine as glucose or fructose to subsequently obtain energy from them. But each type of carbohydrate will behave differently throughout the digestive tract resulting on and faster or steadier energy boost. There are 3 main factors to take into account: the speed of passage through the stomach, the intestine absorption rate, and the transformation speed from the carbohydrate into energy.

Speed of passage through the stomach

The first difference between carb types will be how fast the different substances will pass through the stomach. There are different factors that affect gastric emptying as seen in Figure 6. In this case the difference will be stablished by each molecule osmolality.

Diagram showing factors that affect gastric emptying
Figure 6 Factors that affect gastric emptying (4).

Osmolality refers to the number of molecules of a substance per kilogram of solution. Briefly:

Diagram explaining Osmolality

Osmolality is negatively related to gastric emptying: the higher the osmolality, the slower it will pass into the intestine. Therefore, the 60 glucose units will pass much faster if they are grouped in the form of maltodextrin than if they are free. An additional problem with high osmolality is that the body will want to lower that osmolality by adding water to the stomach. If instead of 0.1 kg of water we drink 1 kg, the osmolality drops from 600 to 60 for the same amount of free glucose units. This effect will translate into a feeling of stomach bloating that you have probably already felt before after taking a gel composed mainly by glucose.

As we have just seen, the osmolality of simple sugars such as glucose and fructose is greater than that of molecules with longer chains such as maltodextrin. Therefore, more water is needed to make a mixture of simple sugars isotonic. This means that simple sugars have a higher risk of causing gastrointestinal discomfort since their gastric emptying is much slower and they retain more water in the stomach.

The acceleration of gastric emptying was precisely what the researchers focused on for the development of hydrogels. These hydrogels help carbohydrates escape the stomach undetected, leading to faster gastric emptying. The problem with this type of gel is that no research has shown gastric emptying to be the rate-limiting step for carbohydrate absorption (5). It is not surprising that no clear benefit has been so far found to the use of hydrogels on performance, total carbohydrate oxidation or gastrointestinal comfort compared to other traditional methods (6,7). No disadvantaged have been found either.

Cluster dextrin® is also designed to have high solubility and very low osmolality in order to pass quickly through the stomach and so minimize the risk of causing gastrointestinal upset (8).

Intestine absorption rate

The absorption in the intestine of the different carbohydrates is indeed the limiting step for the carbohydrate’s absorption (5). While glucose is absorbed at a rate of 60 g/h, fructose is absorbed at half that rate, 30 g/h. If the intake of these limits is exceeded, both excess glucose and fructose can cause gastrointestinal problems such as diarrhoea, bloating and gas. The intestine can be trained to slowly tolerate larger amounts of glucose and fructose.

The more complex carbohydrates cannot be absorbed directly, they must first be transformed into glucose and fructose units. A series of reactions are carried out in the intestine in order to “release” these units. The more complex the carbohydrates, that is, the more cyclized and branched they are, the longer it will take for the bonds to be broken down to release glucose and fructose. In the case of maltodextrin, it has been seen that it gives a glycaemic spike, that is, the speed which glucose reaches the blood from this molecule to be distributed to the muscles, at a very similar speed or even faster than ingesting glucose alone. This is due to the fact that its speed through the stomach is much faster and that, being a linear chain, the release of glucose molecules in the intestine is very fast.

On the opposite side, as Cluster dextrin®has different types of bonds between its molecules, it will release glucose molecules little by little and therefore lead to a slow but steady energy production.

Carbohydrate transformation into energy

Taking into account the osmolality of carbohydrates that will affect gastric emptying, their complexity which will affect the rate of intestinal absorption and that glucose can be used directly to obtain energy, while fructose must be previously processed by the liver into glucose or lactate in order to be used, we can estimate how long each carbohydrate takes to be available to the body to be transformed into energy, that is, to be in the form of glucose in the blood. This parameter is referred as glycaemic index. Carbohydrates that have a high glycaemic index raise the concentration of glucose in the blood quickly as well as quickly lower it. On the contrary, carbohydrates with a low glycaemic index increase the concentration of glucose in the blood slowly, maintaining it over time and with a much smoother decrease in concentration.

On the following table there is a brief summary of the parameters discussed on this section:

OsmolalityGastric emptyingIntestinal absorptionGlycaemic index
Glucose = dextroseHighSlowFastHigh
Cluster dextrinVery lowVery quickFastMedium
Hydrogels?Very quick??

Conclusion 2:
Depending on the immediacy of energy that we need, we will choose some gels or others. In general, in these ultra-distance races we are not going to need to do a sprint, so gels that provide us with long-lasting energy without large peaks will be the best option.

3. Carbohydrate ratios

Apart from the different types of carbohydrates, the gels will also differ in their percentages of each carbohydrate type. As discussed in the previous article, we must take into account the glucose (maltodextrin): fructose ratio, since if we want to ingest more than 60 g of carbohydrates per hour, we must look for gels that contain fructose. As mentioned, recent studies have shown that combining glucose or maltodextrin:fructose ratios of 1:0.5 increase carbohydrate uptake by up to 120 g per hour (9). Recently, it has been seen that increasing the amount of fructose up to ratios of 1:0.8 improves the efficiency of utilization of ingested carbohydrates, reducing the utilization of carbohydrates stored in the body. In addition, they could reduce the symptoms of stomach bloating and nausea associated with the intake of energy gels (10).

Conclusion 3:
We will preferentially choose gels with glucose:fructose mixtures of 1:0.5 or 1:0.8.

4. Other compounds to consider

Manufacturers are starting to add more and more ergogenic compounds, that is, compounds that help increasing sports performance, reducing fatigue or accelerating recovery. We must be cautious and not base our gel choice depending on the ergogenic effect that gels could have. Do not let yourself be carried away by the advertising or claims companies do towards their gels since, even though a compound has been identified as ergogenic, the dose and timing of administration are essential. Some of the compounds added in the analysed gels have been electrolytes, caffeine, citrates, antioxidants, nitrates or amino acids. Very briefly, the contribution of electrolytes and caffeine in gels during races can help us, on the other hand, there is no evidence that citrates, antioxidants, nitrates and amino acids can help us if they are taken during the race and in the dose that these gels currently contain.

Conclusion 4:
We must be careful when choosing gels, letting ourselves be carried away by the manufacturers’ advertising. Choose the gels depending on the carbohydrates and if you are interested in adding an ergogenic compound, it is better to investigate and take them separately and at the right time and dose.

5. Analysis of commercial energy gels

Next, I show you a table with the gels that I think are most commonly used. For the analysis I have taken into account the type of carbohydrate and the ratio of the different carbohydrates. The data appears per 100 g of product and per serving. One serving means a full gel. This makes easier the comparison between gels as different gels contains different amount of product.

As an extra, I have collected data on whether they contain sodium or other ingredients to take into account. The extra ingredients have been taken into account to lower the ranking position of the gel in cases when they do not really have ergogenic effect or are harmful additives.

PositionGELEnergy per
100g / portion
Amount of carbs per 100g / portion% carbsType of carbsfructose : maltodextrin
Sodium per
100g / portion
Other ingredients to take into account
(60 ml)
673/ 158 kcal66/ 40 g53%Maltodextrin and fructose0,8:15/3 mgCitrates
Gel 30
(60 ml)
171/ 128 kcal
40/ 30 gMaltodextrin and fructose0,8:10L-citrulina & L-arginina
GEL 100
(40 g)
250/ 100 kcal62,5/ 25 g60%Glucose and fructose0,8:150/ 20 mgNo
(32 g)
313/ 100 kcal72/ 23 g69%Maltodextrin and fructose0,5:1172/ 55 mgAmino acids (Leucine, Valine,
Isoleucine) and citrates
(45 g)
253/ 114 kcal64/ 29 g64%Maltodextrin and fructose0,5:1109/ 49 mgCitrates
Power GEL Original
(41 g)
252/ 103 kcal63/ 26 g63%Maltodextrin, fructose and glucose syrup0,5:1503/ 206 mg
(60 ml)
148/ 89 kcal37/ 22 g-Dextrose (D.E.6-D.E.19) and highly branched Cluster Dextrin®0:112/ 7 mgSucralose
Isotonic energy gel
(60 ml)
144/ 87 kcal36/ 22 g33%Maltodextrin0:10,4/0,4 mgAcesulfame K
7Santa Madre
(55 g)
121 kcal30 g-Maltodextrin0:140 mgBulking agent: glycerine
Acidulant: citric acid
Sodium chloride
Preservatives: Potassium Sorbate and Sodium Benzoate
L-ascorbic acid (vitamin C)
Natural flavours
Sweetener: Sucralose
(34 g)
294/ 100 kcal74/ 25 g73%Maltodextrin and cane sugar?265/ 90 mgCitrates
Long distance gel
(32 g)
280/ 88 kcal70/ 22 g69%Glucose syrup and maltodextrin0:1156/ 52 mgCitrates, vitamins E, B1, B6 y B12, amino acids (leucine, isoleucine, valine) caffeine
Energy gel
(35 g)
113 kcal
81/ 28 g
80%Glucose syrup0:10 mgVitamins C and B1, Preservatives
Female cyclist Nerea Pajares Moran

Nerea Pajares Morán

Graduate Biotechnology, Graduate Human nutrition and dietetics, Master Biomedical Research


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8. AKII, Hiroshi & Kometani, Takashi & NISHIMURA, Takahisa & Kuriki, Takashi & FUSHIKI, Tohru. (2004). A Sports Drink Based on Highly Branched Cyclic Dextrin Generates Few Gastrointestinal Disorders in Untrained Men during Bicycle Exercise. Food Science and Technology Research – FOOD SCI TECHNOL RES. 10. 428-431.

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