There is no way around the gut

3. July 2019

When your stomach doesn’t want to cooperate, physical performance turns into torture. And the flip side of the token: healthy intestines help athletes soar to new heights. Naturopath and triathlete Christian Harzenmoser explains how the intestines can be put into tip-top shape.

‘All disease begins in your gut’ surmised even Hippocrates back in his day and indeed, scientific studies in recent years have confirmed that the human gut is in direct contact with the emotional centre of our brains. The gut is also our main communication interface with the environment and a crucial organ of the immune system. Since they exhibit a certain permeability in order to absorb nutrients, their huge, approximately 300- to 500-square-metre surface poses the risk of allowing harmful substances or pathogens, for example through the digestion of food, to make it into the body. 

The considerable importance of healthy intestines is also clear to see in endurance sports. Athletes are often preoccupied by their gut for two completely different reasons. Firstly, stomach issues are probably the complaint most commonly responsible for an athlete’s inability to unleash their top performance during long and intense endurance competitions. And secondly, athletes with chronic gastrointestinal troubles do not even manage to achieve maximum performance in the first place. Christian Harzenmoser, a triathlete and naturopath from Niederteufen, knows the intestinal issue from both sides, both from working with athletes in his day-to-day work and as an endurance athlete himself. 

Christian Harzenmoser, at the finish line of a long competition like a marathon or Ironman, athletes often complain of stomach problems, abdominal cramps, and discomfort. Why is that?

Intense physical exertion hinders the circulation of blood in your gastrointestinal tract and thus also significantly impairs its performance. Under top performance conditions, oxygen is used primarily for the functioning of the muscles. And the greater the exertion, the less the stomach can fulfil the tasks demanded of it due to the reduced oxygen supply. This may result in it temporarily abandoning its duties, thus leading to the aforementioned symptoms, such as cramps, discomfort, and even vomiting. 




Athletes experience an inner conflict during endurance sports: on the one hand, they burn a lot of energy through their exertion and need to recover it. On the other hand, their intestines have limited capacity to digest the energy-yielding sustenance. What is the best way of handling this contradiction? 

It is crucial to do some testing out in order to identify the right food intake during your training, because what type of nourishment affects your performance in what ways is highly individual. The right diet is a question of feeling and experience, but also depends on the athlete’s ambitions. It also matters what your goals are and what kind of sport you are doing. If you are fighting for every second in an Olympic triathlon, there is no time left to eat. If, however, you’re taking it easy and just want to reach the finish line, you can have a snack without any problems. The duration also plays a role: the longer a physical exertion lasts, the more solid foods can be taken into consideration or a mix of salty and sweet things. If you’re on the move for several hours, you often want to have some variety in your food and drink and chew on something. Because you should not forget: whether you eat enough or not also depends on the taste. 

Is liquid food the most convenient for intense physical exertion?

Yes, definitely. Liquid food is easier to digest than solid food and is more easily absorbed by the stomach. In sporting events up to approximately Ironman duration, competitive athletes primarily take in their nourishment in liquid form. Usually with a combination of water and gels or a mix of sports drinks, water, and gels. It must be noted that all additives contained in sports drinks or gels, such as L-carnitine, may trigger intolerances, so you must therefore find out in advance which products from which manufacturer your body tolerates and which it does not. It is furthermore essential for you to have done some testing out during training at the planned competition pace – and not during a more easy-going session – in order to find the right nutrition plan for you. If you prefer solid food, you should make sure you divide it up into as many small to very small portions as possible.




How should you react when you experience stomach issues during physical activities?

The first natural step is to take your pace down a notch. This will often calm down your stomach again quickly. If you just can’t take it any more, you need to cease your activity. It is always good to consume liquids, particularly water. And for some people an occasional sip of cola can also help.

Your diet and your stomach’s reaction under strain are one thing, while generally healthy or less than fully functional intestines on a day-to-day basis are another. How important are the intestines for us humans?

There is no way around the gut! There’s a reason why it is often referred to the brain of your belly. The intestines affect our immune systems, minds, livers, endocrine systems, and much more. Serotonin, for example, is considered to be a hormone associated with well-being, as it relaxes us, makes us feel good, and impacts our endorphins. 90% of serotonin is produced in the gut and only 10% in the human brain. 

How many people are faced with intestinal problems?

That depends on the benchmark. Most people are relatively content with their gut, but I think they underestimate the potential of a perfectly functioning one and often do not associate many symptoms with their intestines which do in fact originate there. Most people view a seventy percent functional capability already as good. Irritable bowel syndrome is an obvious problem, but allergies or certain intolerances are often not regarded as such. 

What should athletes pay heed to in their everyday nutrition?

The foundation is a diet rich in bases and as gluten-free as possible, with potatoes, nuts, fruits, salad, and vegetables. A favourable acid-base balance should be maintained. Therefore, athletes should limit their consumption of acidic foods such as alcohol, animal proteins, cheese, sausage products, French fries, white-flour products, cola, or other carbonated beverages. Stress and medications also adversely impact the acid-base balance.




What effect does stress have on your gut?

A very big one. Stress, anxiety, nervousness – all this literally upsets your stomach. In such situations, your body’s systems are required for other purposes and your digestive processes are cranked down to a minimum, causing your gastrointestinal system to quickly start protesting when the factors of top athletic performance, nervousness, and food intake have to be reconciled. For this reason, athletes should acquire mental techniques to promote relaxation and prevent their nervousness from becoming overly intense.

What are the treatment options in the event of intestinal problems?

It is always important to figure out the factors causing your symptoms on an individual basis. In the case of allergies or intolerances, it is recommended to change your diet so as to eliminate the triggering substances. 


Christian Harzenmoser has run a naturopathy practice in Niederteufen for 23 years (, where he regularly also treats athletes.