For years, lactose has been one of the least considered carbohydrates in sports nutrition. Its presence in dairy products and the high prevalence of intolerance have led many athletes to directly associate it with digestive discomfort or poorer performance. However, the most recent scientific research raises an interesting question: could lactose play a different role when used strategically during exercise?
The answer is not yet definitive, but studies published in recent years show promising results. Lactose not only provides glucose but also galactose, two monosaccharides that follow different metabolic pathways after absorption. This characteristic has piqued the interest of researchers specialized in sports nutrition, who are studying whether this combination could help increase carbohydrate availability during prolonged efforts.
In this article, we analyze what the current evidence says about lactose and sport, why many runners and cyclists avoid it, what role it could play in modern nutrition strategies for endurance events, and how we at FANTÉ have considered it a plausible option.
What is lactose and why does it matter in sports nutrition?
Lactose is the main naturally occurring sugar in milk and dairy products. It is composed of a glucose molecule and a galactose molecule, linked by a bond that must be broken by the lactase enzyme before both sugars can be absorbed in the small intestine.
Once hydrolyzed, glucose and galactose enter the bloodstream and can be used as an energy source. Glucose is the preferred fuel during moderate- and high-intensity exercise, while galactose follows a different metabolic pathway before being incorporated into energy metabolism.
It is precisely this difference that has sparked research interest. For years, most strategies to increase carbohydrate intake during exercise have been based on combining maltodextrin and fructose, as they use different intestinal transporters and allow for an increase in the total amount of carbohydrates absorbed per hour.
Luis Martínez, nutritionist and founder of FANTÉ, points out that modern strategies must adapt to the characteristics of each athlete and that the goal is to optimize energy supply by using different intestinal absorption pathways when the duration and intensity of exercise require it.
In this context, a new line of research emerges: to study whether the combination of lactose and maltodextrin can become an interesting alternative for certain endurance athletes.
Why endurance athletes avoid lactose (and when they are right)
The relationship between lactose and sport has traditionally been marked by mistrust. This is not coincidental, as gastrointestinal problems are very common during endurance events, and any food associated with digestive discomfort is usually eliminated from the nutritional plan.
Research shows that between 30% and 90% of runners, cyclists, or triathletes experience some gastrointestinal symptoms during long training sessions or competitions. Nausea, bloating, abdominal pain, urgency to defecate, or diarrhea can affect both performance and the ability to maintain an adequate carbohydrate intake strategy.
However, attributing all these discomforts exclusively to lactose would be an oversimplification. The appearance of symptoms depends on numerous factors, such as exercise intensity, reduced intestinal blood flow, mechanical stress, hydration, the amount of carbohydrates ingested, and individual tolerance.
Therefore, more and more researchers argue that nutritional strategies should be trained just like physical capacity, allowing the digestive system to progressively adapt to larger amounts of carbohydrates during exercise.
Lactose intolerance vs. sensitivity during exercise
One of the most common mistakes is to confuse lactose intolerance with the digestive discomfort inherent in exercise.
Lactose intolerance occurs when the body produces too little lactase enzyme and cannot fully hydrolyze this sugar. As a result, some of the lactose reaches the colon undigested, where it is fermented by intestinal microbiota, producing gas, abdominal distension, or diarrhea.
In contrast, an athlete may experience gastrointestinal discomfort during a competition without having intolerance. Intense exercise temporarily alters digestive function and reduces blood flow to the intestine, favoring the appearance of symptoms even with foods that are normally well tolerated.
For this reason, current evidence recommends individualizing nutritional strategies and avoiding generalizations. A food well tolerated by one athlete may not be for another, especially when carbohydrate intake exceeds 90 grams per hour.
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The real problem: absorption speed, not the sugar
For many years, it was thought that the main limit to ingesting large quantities of carbohydrates was the type of sugar used. Today we know that the true limiting factor is usually found in the intestine's ability to absorb and transport them.
When all carbohydrates use the same intestinal transporter, it can become saturated, reducing the absorption rate and increasing the amount of carbohydrates that remain in the intestine, favoring the appearance of digestive discomfort.
For this reason, mixtures of maltodextrin and fructose emerged, which utilize different transporters. Studies published by Odell and collaborators now raise the possibility that glucose and galactose derived from lactose could represent a distinct metabolic pathway that deserves further investigation.
Although more studies are still needed to confirm its practical application in competition, this hypothesis has opened a new line of research within lactose and sport, especially in strategies aimed at athletes seeking to ingest very high amounts of carbohydrates during several-hour efforts.
Lactose and sport: how it acts as an energy source
Until a few years ago, most sports nutrition strategies focused on combining glucose, maltodextrin, and fructose to increase the amount of carbohydrates the body could use during exercise. However, recent research has begun to explore new alternatives to further optimize energy supply in prolonged efforts.
In this context, the relationship between lactose and sport has aroused growing interest. Once lactose is hydrolyzed by the lactase enzyme, it releases glucose and galactose, two monosaccharides that can be incorporated into energy metabolism through different pathways. This characteristic has led to research into whether the combination of lactose with other carbohydrates could offer advantages in advanced nutritional strategies.
It is important to note that, as of today, this hypothesis is still under investigation. Although the published results are promising, more studies are still needed in athletes and under real competition conditions before establishing general recommendations.
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The hypothesis: lactose + maltodextrin as a different combination from maltodextrin + fructose
Most current energy gels use combinations of maltodextrin and fructose because they utilize different intestinal transporters. This allows for an increase in the total amount of carbohydrates absorbed and subsequently oxidized as an energy source during exercise.
Studies by Odell and collaborators (2020) demonstrated that exogenous carbohydrate oxidation obtained from lactose was comparable to that observed with sucrose during exercise. Subsequently, the same research group found that glucose and galactose ingested together could also be effectively oxidized during prolonged efforts (Odell et al., 2022).
These results do not mean that lactose is superior to traditional strategies. What they suggest is that it can represent an additional pathway to expand carbohydrate supply options, especially for athletes who seek to ingest high amounts per hour and who tolerate this sugar correctly.
This approach aligns with the concept of personalized sports nutrition advocated by Asker Jeukendrup, according to which the optimal strategy depends on the type of exercise, duration, intensity, and digestive response of each athlete.
Can lactose help preserve muscle glycogen in prolonged efforts?
One of the main objectives of consuming carbohydrates during an endurance event is to maintain blood glucose availability and reduce the utilization of muscle and liver glycogen stores.
Scientific evidence has shown that increasing the availability of exogenous carbohydrates helps maintain performance during prolonged exercise. However, there is not yet enough evidence to state that lactose preserves muscle glycogen better than other carbohydrate combinations.
What is being investigated is whether the incorporation of glucose and galactose from lactose could help increase the total availability of carbohydrates when combined with other energy sources.
Therefore, the current hypothesis is not to replace traditional strategies, but to expand the possibilities for athletes who tolerate lactose well and want to train for high carbohydrate intake during long-duration competitions.
Endurance athlete and lactose: who can benefit?
Not all athletes will respond the same way to a lactose-based strategy. Digestive tolerance remains one of the most important factors when planning nutrition during training and competitions.
An endurance athlete consuming lactose can obtain very different results depending on their ability to digest this sugar, the amount ingested, and prior training of the digestive system.
The profiles that could benefit from this line of research are mainly:
- Feeling of energy depletion: the sudden drop in available glucose causes that characteristic sensation of "hitting the wall."
- Premature fatigue: the muscle lacks the necessary substrate to maintain effort intensity.
- Poor digestive tolerance: irregular or late intake makes absorption difficult and can cause gastrointestinal discomfort.
- Need to ingest too many gels too soon: without an established guideline, the athlete resorts to gels reactively, compromising the nutritional strategy.
In all these cases, the objective is to progressively increase the digestive system's capacity to tolerate large amounts of carbohydrates, while reducing the risk of gastrointestinal discomfort.
However, athletes with diagnosed lactose intolerance should exercise greater caution. The response varies greatly among individuals, and scientific evidence recommends testing any nutritional strategy during training before using it in competition.
Furthermore, it should be remembered that digestive discomfort during exercise is not always due to lactose. Factors such as exercise intensity, heat, dehydration, competitive stress, or excessive carbohydrate intake can also trigger gastrointestinal symptoms.
Precisely for this reason, international guidelines recommend training the gut in the same way that aerobic capacity is trained, progressively adapting the amounts of carbohydrates ingested during long training sessions.
FANTÉ's GEL 120 Lactose: the first gel that leverages this CHO for performance
With the aim of continuing to research new sports nutrition strategies, FANTÉ has developed GEL 120 Lactose, an experimental product designed within the FANTÉ LAB PROJECT 01 research project.
Unlike conventional gels made exclusively with maltodextrin and fructose, this product incorporates lactose as part of its formulation to study its behavior during exercise and evaluate its gastrointestinal tolerance in endurance athletes.
Each gel provides 30 grams of carbohydrates and 200 mg of sodium, integrating into individualized nutritional strategies for long-duration training and competitions.
It is important to note that the product's objective is not to demonstrate an already confirmed benefit, but to contribute to generating scientific evidence on a line of research that is attracting growing international interest.
If you wish to delve deeper into this research, you can consult the study on lactose and performance developed by FANTÉ LAB, which explains the project's objective and how interested athletes can participate.
If you are looking for other solutions to train your nutritional strategy during competition, you can also discover the entire range of FANTÉ energy gels.
Bibliography
The information presented in this article is based on the scientific evidence available to date on carbohydrate metabolism, sports nutrition, and digestive physiology during exercise.
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