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10 Ways to Avoid Gastrointestinal Problems

Not all GI problems are avoidable, but taking these 10 steps will minimise your chances of developing them.

Unfortunately, gastrointestinal problems are very common, especially among endurance athletes and they can easily ruin a race. Although we refer to these problems as “gastrointestinal problems”, “GI Problems” or “stomach problems” there is actually a wide range of issues that fall into this category and different symptoms may have different causes. Our understanding of why these problems occur is incomplete. We also don’t know why some athletes are more prone to develop these issues than others. However, we do know a number of ways to reduce the risk. Not all of these suggestions may work for everyone, but hopefully every sufferer can find one or two ways out of this list that will work for them. The guidelines below are based on limited research, but anecdotally these guidelines seem to be effective.


10 Steps to Avoid Gastrointestinal Problems Infographic


Avoid high-fibre foods in the day or even days before competition

For the athlete in training, a diet with adequate fibre will help to keep the bowel regular. Fibre before race day is different. By definition, fibre is not digestible, so any fibre that is eaten essentially passes through the intestinal tract. Increased bowel movements during exercise are not desirable and will accelerate fluid loss. It may also result in unnecessary gas production which might cause cramping. Especially for those individuals who are prone to develop GI-symptoms, a low-fibre diet the day before (or even a couple of days before) is recommended. Choose processed white foods, like regular pasta, white rice, and plain bagels instead of wholegrain bread, high-fibre cereals, oats and brown rice. Check the food labels for fibre content. Most fruits and vegetables are high in fibre but there are a few exceptions: zucchini, tomatoes, olives, grapes, and grapefruit all have less than one gram of fibre per serving.


Choose sports nutrition products with a neutral pH

Unfortunately, many sports nutrition products, especially drinks and gels have a very high acidity (low pH). Often the acidity is increased to improve shelf life of a product. However, a low pH also seems to affect GI problems with athletes reporting more problems with low pH products. A neutral pH may help. Unfortunately, not many products on the market are formulated with a low pH and most brands do not report the pH of their products. Neversecond's C30 Sports Drink is a great choice as it has a neutral pH.


Choose multiple transportable carbohydrates

Combinations of carbohydrates (multiple transportable carbohydrates, for example glucose and fructose, or maltodextrin and fructose) are more effectively absorbed and linked to fewer GI problems, especially when ingested in larger amounts. The reason is that they are more completely absorbed and therefore the residual volume (what is left in the intestine is smaller). All Neversecond C-Series Products are formulated with multiple transportable carbohydrates.


Avoid slow carbs

Slow carbs typically are absorbed slower and this remains in the GI tract longer. This can cause accumulation of carbohydrates in the gut and generally this is linked with GI problems. Smaller amounts may not be a problem, but they will also provide little benefit. (See also ‘avoid fructose-only foods’ below).


Avoid aspirin and non-steroidal anti-inflammatory drugs (NSAIDs)

Both aspirin and NSAIDs are commonly shown to increase intestinal permeability (protective barrier function of the gut is compromised) and may increase the incidence of GI complaints. The use of NSAIDs in the pre-race period should be discouraged.


Avoid milk products

Avoid products that contain lactose as even mild lactose intolerance can cause problems during exercise. For instance, it is possible to avoid milk completely or get lactose-free milk. Soy, rice, and almond milks generally don't contain lactose. This advice will only work for a limited number of people, but it is worth trying.


Avoid fructose-only foods

Fructose is found in most fruits, and although fruits are also high in fibre and this may be the reason that fruit intake is sometimes associated with GI-problems. Some fruit juices are almost exclusively fructose. It is known for a long time that fructose when taken as the only carbohydrate source, this can increase the risk of GI-distress.


Avoid dehydration

Dehydration can exacerbate GI-symptoms. It is important to avoid dehydration. Start the race well hydrated.


Practice any new nutrition strategies

Make sure to experiment with your pre-race and race-day nutrition plan many times prior to race day. This will allow you to figure out what does and does not work for you, and to reduce the chances that GI issues will ruin your race.


Training the gut is another practice

If your gut is adapted to the foods (and volumes!) you consume during a race, you are less likely to get stomach problems. If you are avoiding carbohydrate in daily life, your intestines will respond by reducing intestinal transporter numbers so your ability to absorb carbohydrate is reduced. On race day you may not be able to absorb all of the ingested and this may cause GI-issues. The advice is therefore not to restrict carbohydrate intake and regularly consume carbohydrates during training.


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  • de Oliveira, E. P., Burini, R. C., Jeukendrup, A. 2014. Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations. Sports Med 44 Suppl 1: S79-85.



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