Gut Health and Athletic Performance

Gut health is an important part of athletic performance. Not only does your gut health impact the way you perform, but your training and athletic performance impacts your gut health. While most athletes have experienced some sort of digestive upset during training or racing, you do not need to have GI symptoms in order to have poor gut health.

Gut health is an important part of athletic performance. Not only does your gut health impact the way you perform, but your training and athletic performance impacts your gut health. While most athletes have experienced some sort of digestive upset during training or racing, you do not need to have GI symptoms in order to have poor gut health.

The most obvious connection is that athletes absorb the nutrients and energy we need through our GI tract. In order for this process to happen properly, food must be broken down with digestive enzymes and the barrier function of the gut must be functioning properly.

More than 70% of the cells of your immune system are in your gut and your gut bacteria have a huge impact on your immune system as well. They regulate inflammation and help to fight off infection. Since inflammation is a normal part of training and racing and is an important part of the healing and recovery process and optimal immune function is a critical part of avoiding illness when stress levels are high (such as during peak training), a well functioning immune system is important for sport performance.

What Does Your Gut Do?

Most of us are aware that our guts are incredibly important because they turn the food we eat into fuel. But what exactly does that involve?

The GI tract (more specifically, your stomach and intestines) is home to millions of bacteria. These bacteria actually outnumber our human cells ten to one. Probiotics refers to a specific type of gut bacteria that are critical to both our gut health and our overall health.

The function of the bacteria that live in our gut is to break down food, recognize pathogens (harmful bacteria, viruses, parasites, etc.), maintain the health of our intestinal lining, help regulate blood sugar, and help with nutrient and mineral absorption. Unfortunately, an optimally functioning gut typically flies under the radar, but one that doesn’t function well gets a lot of attention.

The food we eat is progressively digested as it travels along our digestive tract. The process of digestion is both mechanical and chemical and it releases nutrients along the way. We can’t use whole foods as fuel or absorb nutrients from them, so our bodies break them down into smaller bits that can easily cross the gut barrier.

The lining of your digestive tract is just one cell thick and its job is to let nutrients in while keeping everything else out. Digestion starts when you chew your food (mechanical digestion). That action releases salivary enzymes which being the chemical breakdown of food. As the food travels down your digestive tract it becomes progressively more broken down.

A healthy balance of the right kinds of microorganisms in the gut is critical for health and diet (i.e. the food you eat) is one of the biggest influencers of your gut bacteria.

If your gut is not functioning optimally, it can become “leaky” (more technically called “increased intestinal permeability”). This happens when the cells lining your gut are damaged and allow larger particles in that your body doesn’t recognize as food. This sets off an immune reaction and can cause inflammation.

Increased intestinal permeability is a common problem among endurance athletes (long or intense exercise makes your guts leaky, you can learn more about this by listening to episode 40 of Renegade Endurance Radio here). It can cause everything from mild discomfort such as bloating or heartburn) to more intense pain, diarrhea, and nausea. The effects of increased intestinal permeability are far reaching and it can be a contributing factor to conditions such as allergies, asthma, skin irritation/rashes, IBS, certain autoimmune diseases, and more.

How Your Gut Can Get Damaged

There are several ways that your gut lining and your gut bacteria can become damaged. Antibiotics and other medications kill good bacteria and can irritate the lining of your gut. Environmental chemical exposure the food we eat (especially processed foods and sugar) can also damage your gut.

As mentioned previously, physical activity and exercise can also cause leaky gut. I go into this in more detail in episode 40 of Renegade Endurance Radio, but the gist is that during exercise, blood flow is shunted away from the GI tract to the skin and working muscles. This not only causes increased intestinal permeability but also is thought to be the main cause of the GI symptoms experienced during training and racing.

It is also important to note that NSAIDs, which are commonly used among athletes for mild to moderate pain relief, increase the risk of developing GI symptoms by up to five times and contribute to increased intestinal permeability. You can check out this blog post all about why you should consider avoiding NSAIDs as an athlete and what to use instead.

Got Gut Symptoms?

Research says that around 90% of athletes have experienced GI distress of some kind. In the endurance sports world, the common belief is that you need to replace as many calories as possible with simple carbohydrates. This typically ends up looking like constant consumption of gels and sugary sports drinks. This is meant to spare your glycogen stores and help you race faster for longer. But the problem with this approach is that it ends up overloading the digestive tract when it is already under stress and not functioning well.

Filling your gut with tons of sugar typically ends up leading to dehydration and GI distress (I go into more detail about how and why this happens in episode 40 of Renegade Endurance Radio).

Athletes also spend a fair amount of time in the sympathetic dominant state of “fight or flight.” This state helps us in our athletic pursuits, but it is less than ideal of a well-balanced digestive system. Your body diverts blood flow away from your stomach while you are exercising in order to meet the oxygen and nutrient demands of your muscles.

A nervous system constantly on high alert also creates large amounts of cortisol from your adrenal glands to circulate in your system. Cortisol also causes your body to not prioritize digestion, it can erode the lining of your digestive tract, and it disrupts the production of digestive enzymes and gastric juices which can lead to poor gut function and contributes to increased intestinal permeability.

Gut Health Affects Performance

While it’s hard to understand the impact of something you can’t always see or feel, like optimal gut health, also know that your gut health does impact your overall athletic performance.

Since a majority of your immune system lives in your gut, a compromised digestive system affects your ability to fight off infection. If your gut health is less than optimal there is a greater chance that you’ll get sick. Most athletes don’t like forced time off due to illness. This also means that when you have inflammation in certain areas of your body, your chance of injury is increased. If your muscles aren’t able to repair themselves after a hard workout, you’ll likely end up chronically injured in the long term

Increased intestinal permeability due to high levels of stress, inflammation, or dietary triggers can negatively impact your performance. It impairs nutrient absorption (which impacts your energy production), it can increase insulin resistance, delay recover, and contribute to injuries.

When your gut is leaky and bacteria from your gut end up in your bloodstream, your immune system goes into high alert mode. You get increased systemic inflammation which creates insulin resistance in your muscles and fat. This causes your body to conserve glucose for your immune system to use for fuel, which impacts your ability to use glucose as fuel.

Keeping Your Gut Happy

One of the primary goals of athletes should be to achieve and maintain good gut health and a happy gut microbiome. While most people assume that they can take a pill (like a probiotic) and fix whatever problems they might have with their gut, that is simply not true.

Probably the easiest thing you can do for your gut health is to eat a diet that supports your gut bacteria. This means eating a diet composed mostly of whole foods from a variety of sources. There are foods (such as sugar, many grains, and a few other foods) that are known to be irritating to the gut and can negatively impact the gut microbiome and these foods should be avoided as much as possible. Diet is the biggest influence on our gut microbiome and is responsible for more than 60% of the variation in bacterial species in our gut.

You also want to make sure that you are consuming plenty of fiber (maybe not in the days surrounding a big race though!). Fiber also feeds your gut bacteria and it keeps your digestion moving along.

Making sure that you are managing stress and practicing proper recovery is also important for both your gut health and your immune system. This is especially important during times when training volume or life stress is high.

Probiotics can be helpful if you are trying to heal or improve the balance of bacteria in your gut, however before you start a probiotic supplement, it’s a good idea to speak with your healthcare provider to make sure it’s a good idea for you. Some people find probiotics to do more harm than good. Probiotic foods such as sauerkraut, kombucha, kefir, and yogurt are also a great way to get probiotics in real food forms.

While gut health is something that is not forefront in the minds of most athletes, it is one of the most important things when it comes to health and athletic performance. Since individual is unique, it is difficult to give specific recommendations when it comes to healing and maintaining optimal gut health. However, the pieces I’ve covered here are a good starting place.


If you struggle with gut issues or you think that you gut health may be negatively impacting your athletic performance, it’s best to work with a holistic or functional medicine provider to work on optimizing your gut health. It’s such an important part of overall health and you can often do more harm than good when trying to self treat.

You can also check out my Find Your Perfect Diet course which will help your gut health through optimizing your diet. If you want a more comprehensive approach specifically geared towards athletes, be sure to jump on my email list to be notified when my newest program launches!

 

References:

  1. https://academic.oup.com/jn/article/141/5/769/4600243

  2. https://www.mdpi.com/1422-0067/16/4/7493

  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3337124/