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Triathletes have a reputation for being some of the most heavy supplement users among the vast realm of endurance athletes. Whether that’s because triathletes tend to be more educated or informed than your average endurance athlete or because they tend to have more disposable income than your average endurance athlete remains to be determined. Whatever the case, the right supplement regime can go a long way to optimising performance in the popular endurance sport of triathlon; traditionally considered the most demanding endurance sport.

Much like supplements for bodybuilding and strength training, supplements for triathletes can be divided into three categories, namely before exercise, during exercise and post-exercise. Because the energy demands of triathlon training and races can be very high (particularly in case of Ironman events), adequate fuelling before, during and after are all equally important. When faced with daily training sessions (often twice per day), your average competitive triathlete is always racing against time to adequately refuel for the next training session or race. The quality of recover invariably determines the quality of performance in the next training session or race.

Supplements Before Exercise

The particular type of supplement best suited to a triathlete before exercise depends on a number of factors. These include the timing of the intake proximal to exercise, the training phase an athlete is in (i.e. taper, heavy, overload) and the goals of the particular training session1.

3-4 Hours Before Exercise

Ingesting carbohydrate 3-4 hours before exercise is a useful practice when maximum performance is the goal of the exercise session or if an athlete is about to engage in prolonged exercise (i.e. longer than 2 hours)1. Alternatively, when a triathlete has just completed an intense or prolonged workout in the previous 12 hours, then intake of carbohydrate in the 3-4 hours prior to exercise can be crucial in replenishing muscle glycogen stores from the previous session2.

Carbohydrate Consumption <60min Before Exercise

There is some debate as to whether ingesting carbohydrates within 60 minutes of exercise is beneficial or not. When ingesting carbohydrates within 60 minutes of exercise, certain individuals are prone to a condition called reactive or rebound hypoglycaemia3. This phenomena occurs when there is a pronounced temporary fall in blood glucose (i.e. below normal levels) associated with the consumption of carbohydrate and the onset of exercise. It is thought to occur as the result of the combination of increased muscle glucose uptake and reduced liver glucose output associated with the onset of exercise. There is also concern that ingesting carbohydrates within 60 minutes of exercise can lead to hyperinsulinaemia, which inhibits fat oxidation and breakdown4. Despite these concerns, a study measuring the possible negative impact of ingesting carbohydrate in the 60 minutes prior to exercise on performance did not find any negative effects. So it appears that the choice of whether or not to consume carbohydrates in the 60 minutes preceding exercise is up to the discretion of the individual and their particular susceptibility to rebound hypoglycaemia.

Aside from carbohydrate ingestion prior to exercise, there are several substances that can provide added benefit for triathletes when consumed prior to exercise. These are covered below.


Caffeine is arguably the most tried and true pre exercise supplement for endurance athletes such as triathletes. Dosage ranges from 3-6mg/kg bodyweight and most studies have athletes take it 1 hour before exercise6. There’s also research showing it makes very little difference whether the caffeine is consumed in the form of coffee or just in pure supplemental form7. Some reviews have suggested that in endurance athletes, the ergogenic effect of caffeine can be enhanced by abstaining for a period of 7 days6. Something to consider if not addicted to caffeine!


Commonly dubbed as ‘nature’s EPO’, beetroot is a popular supplement among endurance athletes and is one of the few supplements that must be taken 1-2 hours before exercise for it to work properly. This is because nitrate from beetroot takes up to 2.5 hours to appreciably boost blood levels of nitric oxide. Studies have shown that beetroot improves endurance by reducing the oxygen cost of exercise at a range of training intensities8, 9. Some very recent studies have even hinted at the possibility of additive performance benefits when combining beetroot with caffeine12.


Supplemental protein prior to exercise is a consideration for triathletes engaged in low glycogen training sessions; popularly termed ‘Train Low-Compete High’. Studies have shown that consuming a protein supplement before such sessions helps to prevent the tendency for muscle breakdown that can occur when doing this type of training10, 11. Whey protein powders are the preferred type of supplements in these instances.

Supplements for Triathletes During Exercise

Intra workout supplementation is possibly the most important area of supplementation in triathlon, particularly in half Ironman’s and full Ironman races, where competitors can be exercising anywhere from 4 to 17hrs. It is also the most challenging area of supplementation because nutritional needs are highly individualised. One of the central issues with supplementation during triathlon is gastrointestinal function. Certain athletes are prone to gastrointestinal distress more than others. For such triathletes, it’s important to understand the factors that typically trigger gastrointestinal upset and to devise an appropriate supplement strategy prior to competition.

Factors Affecting Gastrointestinal Function During Exercise

Studies have documented the high incidence of gastrointestinal complaints that can occur during a half ironman and full Ironman triathlons13, 16. These studies found that gastrointestinal symptoms were more likely to occur with the ingestion of fibre, fat, protein and concentrated solutions13. In particular, sports/electrolyte drinks with a very high osmolality seem to be problematic.

Carbohydrate Mix and Absorption During Exercise

One of the key factors thought to affect absorption of carbohydrate during exercise is the particular mix of carbohydrates1. For example, glucose and fructose are two types of sugars/carbohydrates that are absorbed in the gut via different carriers1. As such, studies have shown that a greater rate of carbohydrate absorption can be achieved when a mix of glucose and fructose is used as opposed to just glucose14. However to make matters more complicated, there are a number of individuals for whom fructose ingestion seems to result in bloating and abdominal distention15. Such individuals are said to suffer from fructose malabsorption.

Therefore it is important that triathletes experiment with different sports drinks and energy gels during training to determine which ones work best. PowerBar Gels are one example of a gel that contains a 2:1 ratio of glucose to fructose and therefore is ideal for those triathletes who don't suffer from fructose malabsorption. On the other hand, GU Energy Gels are another popular gel which have a much lower content of fructose, and therefore may be better tolerated by those with fructose malabsorption.

Recommended Carbohydrate Intake for Triathletes During Exercise

Historically, sports scientists believed that humans couldn’t absorb more than 60g of carbohydrate per hour. This was until they discovered that including a mix of two different carbohydrates in the form of glucose and fructose increases absorption capacity. As such, studies have shown that some athletes can absorb over 100g of carbohydrate per hour when delivered in form of glucose and fructose (with a 2:1 ratio being the most studied). For training sessions or exercise lasting less than 2 hours, sports scientists still recommend that triathletes consume around 60g of carbohydrate per hour. However for longer events such as half and full-Ironmans, the recommendation is to consume up to 100g per hour. This is because after two hours of exercise, carbohydrate stores in the body (i.e. glycogen) become depleted and therefore triathletes need to ingest as much carbohydrate as can be tolerated so as to prevent the detrimental effects of depleted carbohydrate stores on performance.

Supplements to Imrpove Gut Function During Exercise

As highlighted above, endurance exercise is known to be associated with gastrointestinal complaints, especially when its prolonged in nature or performed with a high degree of intensity19. During maximal exercise, splanchnic (i.e. intestines) blood flow may be reduced by up to 80 % to provide sufficient blood to working muscles. For example, one study in the early 90’s found that in exhausting endurance events like triathlon, 30-50% of participants experienced one or more gastrointestinal symptoms17. This phenomena is thought to arise primarily because of reduced blood flow to the gastrointestinal tract19. Therefore, one of the target areas of supplementation in triathletes are those that can help to offset gastrointestinal upsets during exercise.


Citrulline has emerged as a promising agent for preventing the reduction in blood flow to intestines during exercise and the associated gastrointestinal dysfunction. Local availability of nitric oxide is known to be an important factor for enhancing circulation in the intestines. This is the precise reason why citrulline has been studied and shown to act as a more effective booster of nitric oxide than arginine. For example, a recent study published in 2014 showed that 10g of citrulline prevented the decrease in blood flow to the gut normally associated with intense exercise18. It also served to reduce markers of intestinal injury associated with prolonged intense exercise18.


Increased intestinal permeability is another key casue of gastrointestinal dysfunction during endurance exercise. Traditionally known for its immune boosting properties, colostrum has also been shown to prevent the increase in intestinal permeability associated with prolonged exercise in the heat20.

Nitric Oxide

As highlighted above, nitric oxide plays a key role in regulating blood flow in the intestines. As such, sports scientists believe that supplemental nitric oxide may be of value in alleviating the negative effects of prolonged exercise on gut function. However, with the exception of citrulline, there haven’t been any studies exploring this. Nitrate from beetroot is the most obvious candidate for study as it has reliably been shown to boost blood levels of nitric oxide.


Glutamine is reknowned for the critical role it plays in regulating the growth and health of enterocytes (the name given to the absorptive cells within the intestines). Glutamine also plays a key role in regulating intestinal barrier function and can improve the antioxidant status of enterocytes. While studies in humans regarding glutamine’s role in protecting the gut during exercise are skim, there are several studies in rat models that show it can be very effective. For this reason, it is included here as a key supplement for preventing gastrointestinal complaints during exercise.

Food Consumption Guidelines During Endurance Exercise

When it comes to food, there are some general guidelines that may help prevent gastrointestinal complaints. For example, fiber, fat, protein, and fructose have all been associated with a greater risk of developing gastrointestinal symptoms. Researchers from Belgium published a study back in 1992 showing that gastrointestinal problems were more likely to occur when triathletes ingested foods high in fiber, fat, protein and concentrated carbohydrate solutions during a half-ironman triathlon22. Most energy bars tend to follow these guidelines in terms of their macronutrient composition, but there are some which have a relatively high fructose content and therefore may pose a problem for individuals with fructose malabsorption. As with everything, its best to practice your nutrition strategy in training before race day.

Post-Exercise Supplements for Triathletes

Because of its prolonged nature, triathletes often have depleted or close to depleted glycogen stores after training or racing. As such, correct selection of post-workout supplementation can go a long way to improving recovery and performance for the next training session or race. As highlighted above, however, there is a emerging trend for endurance athletes to employ a train low-compete high approach, which typically involves abstaining from carbohydrate ingestion in the hours following a training session. In such situations, it is increasingly popular for triathletes to use a protein supplement which has been shown to stimulate muscle protein synthesis while not diminishing any of the favourable training adaptations shown to occur with low glycogen training.

Carbohydrate & Protein Supplements for Triathletes

A number of studies show carbohydrate and protein supplements following endurance exercise provide the best solution for simultaneously replenishing glycogen stores, aiding muscle repair and stimulating muscle protein synthesis. More specifically, whey protein hydrolysate supplements have been shown to confer additional benefits, particularly with regard to replenishing glycogen stores23-25. Studies show that whey protein hydrolysates stimulate a higher insulin release, which is thought to be a key mechanism by which it confers greater glycogen synthesis over normal whey protein25. In fact, when carbohydrate is consumed at a level of 0.8g/kg bodyweight together with 0.4g/kg bodyweight of whey protein hydrolysate, it seems to confer the same stimulus to glycogen synthesis as 1.2g/kg of carbohydrate alone23-25, 28, 29. Herein lies the advantage of a combined carbohydrate and whey protein hydrolysate, in that it allows triathletes to consume less carbohydrate without negatively impacting glycogen resynthesis while simultaneously repairing muscle damage and stimulating muscle protein synthesis.

Branched-Chain Amino Acids for Triathletes

While very popular for strength and power athletes, BCAA supplements can also be beneficial for endurance athletes such as triathletes. For example, one study has showed endurance athletes performed better when exercising in a glycogen-depleted state and supplemented with BCAAs26. Yet another study showed that use of a BCAA supplement for 7 days lead to improved lactate threshold in a group of endurance athletes27.

Glutamine and colostrum can also be beneficial when taken post-exercise; mainly as a means of preventing the drop in immune function that can occur with prolonged and/or intense endurance exercise. Otherwise, carbohydrate and whey protein supplements should form the core of post-workout supplements for triathletes.

Supplements for Triathletes Into the Future

Sports nutrition research with triathletes and other endurance athletes such as cyclists and runners continues to progress at a rapid pace. This means we can expect to see endurance supplements evolve into the future. At the same time, we can expect to see nutrition guidelines for triathletes and endurance athletes become more specific and customised based on the particular goals of the training session and the phase of training.

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