Triathlon nutrition: what a 2005 review teaches about energy, hydration and gut discomfort

You can get out of the water within the planned, pedal well and still find a very different race from the one you trained. Between conditioning and the result there is a continuous task: to be able to provide energy and liquids to the body without turning food into another difficulty of competition.

This relationship is the center of Nutritional Considerations in Triathlon, a review published in 2005 by Asker Jeukendrup, Roy Jentjens and Luke Moseley in Sports Medicine magazine. The authors organized knowledge about food preparation, fueling during exercise, recovery and nutrition-related problems in triathlon. [1]

Reading helps to understand why a nutritional strategy needs to accompany the entire competition. But it requires attention to date: some numerical recommendations, especially on hydration, should not be transported directly to the present. In this editorial, the ideas of the article and subsequent contextualization are identified separately.

What kind of evidence does this article offer?

The work is a narrative review. The authors discuss already published research and propose interpretations and orientations. They did not recruit a new group of triathletes to test, in this article, a single feeding protocol.

This changes the way you read your results. There is neither a single review sample nor an overall percentage of improvement that represents all studies. The text brings together laboratory experiments, observations in competitions and research with endurance exercises, including cycling and running performed separately.

The review also does not present a search strategy and evaluation of studies in the form of a systematic review. Its contribution is to integrate mechanisms and applications; its limitation is that the discussion does not offer a single quantitative estimate nor a formal classification of the certainty of each recommendation. [1]

1. The problem starts with the available reservations

carbohydrate is mainly stored as glycogen in the muscles and liver. Muscle glycogen provides fuel to exercise; liver helps maintain blood glucose availability. These reserves are limited and participate in the ability to sustain effort.

The article places its reduction among the important factors for fatigue in triathlon. This does not mean that every fall of pace is a lack of carbohydrate. The review itself discusses the role of body temperature and recognizes difficulties in explaining long competitions only by calculations of exhaustion of glycogen. [1]

The teaching is that feeding needs to be planned before the difficulty appears. A strategy started only when the athlete feels a break tries to solve, during the exercise, a problem that was already being built.

Preparing the reserves does not require turning the eve into a test of resistance

The authors review the classic glycogen supercompensation protocol, which combined depletion exercise, few days carbohydrate and a later phase of high intake. They also present studies in which high reserves were achieved with less drastic manipulations. [1]

The conceptual lesson is to separate the purpose of the ritual. The objective is to reach race start with adequate fuel availability. A more exhausting sequence does not become superior just because it seems more elaborate. The protocols discussed in 2005 are part of the history of this investigation, and not an indication to insert a exhaustion training near the competition.

The article also draws attention to the meal prior to race start, especially after night fasting. The choice needs to consider availability of carbohydrates, time to start and digestibility. A meal theoretically enough may fail in practice if the athlete cannot tolerate it. [1]

2. Eating, absorbing and using are different steps

One of the most enlightening parts of the review is the discussion on the path of the carbohydrate ingested. It needs to cross the digestive system, be absorbed and become available for use. The amount consumed does not automatically correspond to the amount used by the muscles at that time.

In 2005, the article recommended approximately 60–70 grams of carbohydrates per hour during the competition, relying on the literature on the use of carbohydrates ingested. But it already discussed studies in which combinations of glucose and fructose increased the oxidation of the carbohydrate provided during the exercise. [1]

The explanation involves different mechanisms of intestinal transport. When the supply depends on a single route, increasing intake may not produce a proportional increase in delivery. Combining sources using different pathways can increase this availability.

There is an important scientific distinction: in that review, the authors also pointed out the need to investigate whether the higher oxidation observed would translate into better performance. Demonstrating a favorable mechanism is not the same as demonstrating a superior competitive result. [1]

Later context: 60–70 g/h is not a universal ceiling

The guidelines consulted by the Australian Institute of Sport differentiate the intake by duration: 30–60 g/h in efforts from 1 to 2.5 hours and up to 90 g/h in events above about 2.5–3 hours. For high rates, they highlight combinations of carbohydrates with different transporters and the practice of strategy in training. They are general references, not a mandatory goal for any athlete or session. [2]

This update helps situate the review historically. Its number should not be treated as a definitive limit, and a higher dose should also not be presented as a guaranteed benefit for all.

3. Cycling is an opportunity for fueling that needs to be organized

During swimming, the opportunities for ingestion are very limited. In running, movement and discomfort may hinder consumption. The bike offers an important opportunity to access and ingest liquids and food; the article highlights this aspect of logistics of the triathlon. [1]

The practical consequence is not trying to consume everything at once in cycling. It is recognizing that the strategy of a stage interferes with the conditions in which the next begins. If the athlete leaves the intake for the race, it can reach the segment with a difficult need to meet. If it concentrates a quantity that does not tolerate on the bike, it can carry the discomfort for the race.

Editorial example: turning a quantity into an executable strategy

Suppose, just to illustrate the calculation, that an individual plan already established provides 60 g of carbohydrates per hour on cycling. A drink with 30 g and a gel with other 30 g complete that amount. The sum, however, does not answer all the questions: can the athlete access the products safely? Tolerates the combination? Is the volume of liquid consistent with the conditions?

If the 60 g are in 500 mL of drink, the concentration will be 12 g by 100 mL, or 12%. If they are in 1 liter, it will be 6%. The amount of carbohydrate is equal, but the formulation and volume are different. This is a mathematical demonstration, not an indication to drink one litre per hour.

The review discussed drinks with 5–8% of carbohydrates as a range favorable to the compromise between liquid delivery and fuel. This does not allow us to conclude that any concentration above it will necessarily cause symptoms. It allows us to understand why evaluating only the grams per hour leaves a part of the strategy out. [1]

4. Intestinal discomfort is not a result detail

Nausea, cramps, vomiting and diarrhea may limit food and pace. The article discusses associations between symptoms and factors such as concentrated solutions, fiber intake, fats or proteins during competition, in addition to physiological conditions of exercise. These associations do not demonstrate that each component is an inevitable cause of discomfort. [1]

The collected studies have quite different frequencies of symptoms. A survey cited included more than 25 thousand competitors from different competitions; another investigated only 30 participants in a long distance competition. These contexts cannot be condensed at a single rate valid for all triathlete. [1]

The effort also redistributes blood flow to the muscles and, depending on the conditions, to the skin. The digestive system performs its task within this scenario. Therefore, the same feeding can be tolerated differently at rest, in a light training and in a demanding competition. [1]

A useful application is to test the strategy under conditions relevant to the competition and record the context. If there were symptoms, it is worth observing quantity, concentration, time of ingestion, intensity and environment. Changing all products simultaneously makes it difficult to identify what made a difference.

A plausible hypothesis still needs to be demonstrated

The review also discusses endotoxemia: the presence of bacterial components in circulation, investigated as a possible explanation for symptoms after prolonged exercises. The authors point out interpretation problems in some studies and report that, in an investigation of triathletes, the intensity of endotoxemia was not related to the incidence or severity of complaints. [1]

Learning goes beyond nutrition: finding a biological change after a non-competition competition that caused the symptoms. It is necessary to demonstrate the relationship, and the review recognizes this uncertainty.

5. Hydration: the point that most requires critical reading

The article emphasizes the possible damage of water loss and proposes to limit the reduction of body mass to approximately 1%. It also associates sodium drinks with the prevention of hyponatremia. These recommendations deserve context, especially because the text itself already recognized the risk of consuming excess liquids and discussed inconclusive results on the protection offered by sodium. [1]

Later context: sodium does not neutralize excess fluid

The international consensus of 2015 on exercise-associated hyponatremia identifies excessive consumption of liquids in relation to losses as a central factor, often combined with reduced ability to eliminate water. Sports drinks with sodium and salt supplements do not prevent the problem when there is excessive intake. The document highlights thirst as guidance to reduce this risk. [3]

This prevents treating the goal of 1% of the review as a universal obligation or forcing weight maintenance. The change in body mass during a prolonged competition does not represent exclusively lost sweat, a limitation that the article itself discusses. [1.3]

For the reader, the essential distinction is that fuel replacement and liquid intake need to be coordinated, but are not the same goal. Drinking more just to achieve a certain amount of carbohydrates can create another problem. AIS also recognizes that fuel and liquid requirements vary differently depending on the situation. [2]

6. Recovery also depends on how long there is until next training

In recovery, the review differentiates the scenario from a new session in a few hours from that in which there is a longer interval. When time is short, starting the replacement of carbohydrates early becomes important for the resynthesis speed of glycogen. In longer periods, the total amount consumed also plays a central role. [1]

This avoids turning post-training into an identical ritual for any activity. A triathlete that ends a session in the morning and will have another demanding in the afternoon faces a need for organization different from that of which it will not train again the next day.

The text also discusses the addition of proteins to carbohydrates. In some studies, it increased the replacement of glycogen; when the intake of carbohydrates was already high, this additional benefit did not appear. This conclusion refers to the outcome glycogen, not to the uselessness of the protein for recovery. The article itself distinguishes fuel replacement from the processes of protein synthesis and repair. [1]

The same care applies to liquids: Ingesting a volume and retaining it are different things. The review examines the role of sodium and feeding in restoring the water balance. Its experimental rehydration protocols should not be confused with an order to consume large volumes quickly after any session. [1]

What does this review allow to take for training?

The merit of the article is to show a chain of connected tasks. Getting there with proper reservations facilitates the start; an executable intake supports continuity; digestive tolerance allows maintaining the strategy; recovery prepares the next session.

To apply this reasoning, the athlete can discuss with his team five questions:

1. How am I gonna get to race start? Consider the previous food and the tolerance to the pre-competition meal.
2. Where will I be able to supply myself? Plan access, transportation and consumption in each segment.
3. What am I really consuming? Add the carbohydrates of drinks and food, without confusing this account with the need for liquids.
4. How do I respond to the strategy? Observe digestive comfort and execution in conditions similar to those of competition.
5. When will I need to be ready again? Organize the recovery according to the next demand.

The answers do not come out of an isolated number of the article. They arise from the combination of evidence, characteristics of competition, practice and individual follow-up. The lasting contribution of this review is to help the athlete understand the stages of the problem and ask better questions about his own preparation.

Limits and transparency

This is a critical and selective synthesis of a publication of 2005. The subsequent contextualization uses the sources [2] and [3], without constituting an exhaustive review of the current literature. There is no new statistical analysis, and the numerical examples of this editorial have not been tested by the article nor represent individual prescriptions.

In their thanks, the authors inform that their research received funding from GlaxoSmithKline Consumer Healthcare. This statement is relevant to the transparency of reading, but does not in itself demonstrate that the conclusions are incorrect. [1]

References

[1] Article analyzed: JEUKENDRUP, A. E.; JENTJENS, R. L. P. G.; MOSELEY, L. Nutritional considerations in triathlon. Sports Medicine, v. 35, n. 2, p. 163–181, 2005. DOI: 10.2165/00007256-200535020-00005. Full text analyzed from the PDF provided.

[2] Context on carbohydrate and logistics: AUSTRALIAN INSTITUTE OF SPORT. Sports drinks: how and when do I use it? Institutional guidelines. Consulted in 14 October 2026.

[3] Context on hydration: HEW-BUTLER, T. et al. Statement of the 3rd International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. British Journal of Sports Medicine, v. 49, n. 22, p. 1432–1446, 2015. DOI: 10.1136/bjsports-2015-095004.

Cada um no seu ritmo. Juntos no caminho.