How Improving Your Gut Can Enhance Your Exercise Potential

This simple dietary change will also boost your overall health

What comes to mind when you think of the relationship between nutrition and athletic performance?

Perhaps you consider protein intake for muscle development or carbohydrate intake or glycogen storage for long-duration exercise? You may focus on fats for low-intensity activity and carbohydrates for high-intensity activity. Macronutrients may not have registered, opting to focus on hydration or total caloric intake instead.

What about the gut microbiota and fiber?

This recent paper highlights current evidence exploring the relationship between the gut microbiota and exercise.

What is the Gut Microbiota?

The gut microbiota consists of approximately 40 trillion bacteria, viruses, archaea, and fungi. You will find these bacteria throughout the gastrointestinal tract, with the largest proportion in the large intestine.

Why is the gut microbiome so important? It plays a large role in our metabolic functions and immunity. It also helps control inflammation, harvest energy, and synthesize vitamins (such as vitamin K and most B vitamins).

We are starting to compile evidence that suggests it may influence our exercise capacity, tolerance, and performance as well.

Observational studies show athletes have greater diversity, an enrichment of beneficial taxa, and more fecal short-chain fatty acids (which may benefit skeletal muscle metabolism). Keep in mind, any correlation can be bidirectional. It’s possible that exercising regularly and at a high capacity may improve the gut microbiota. Studies have shown exercise increases the relative abundance of health-associated taxa.

It’s also possible that athletes eat diets that support the gut more than non-athletes do, improving their exercise performance and capacity. How?

The Gut Unlocks More Exercise Potential

One of the first studies in mice revealed supplementation of a single bacteria strain for four weeks, Bifidobacterium longum, improved fatigue strength, and energy availability. Since then, we have started compiling data in mice and humans that reveal three likely mechanisms for improving exercise performance. Keep in mind, these are largely looking at aerobic exercise.

The first potential driver of improved exercise capacity is a boosted lactate metabolism. Lactate is often thought of as a harmful substance that causes fatigue. I remember being taught lactic acid builds up in the muscle and causes burning and fatigue. This isn’t an accurate portrayal of lactate.

Lactate, not lactic acid, does build up as it is a normal by-product of cell metabolism and exercise. Our muscles use lactate as a major fuel source during exercise. The faster we can use and clear lactate, the higher our endurance (blood lactate threshold is a common tool for measuring endurance capacity).

Oxidizing tissues use lactate to produce ATP (the main source of energy for our cells) and the remainder is converted to glucose by the liver, which can later be used as a glycolytic substrate for skeletal muscle. The gut microbiota may act as an additional lactate consumer site, providing more capacity for exercise.

A greater glycogen storage capacity is the second potential benefit derived from a healthy gut. Glycogen is stored glucose in our muscles and liver that can be used to rapidly provide ATP to our cells. The size of our muscles influences how much we can store but on average, people can store 500 grams in the muscle and 100 grams in the liver. One gram provides roughly 4 calories.

You don’t need Gatorade or running gels for 5 and 10k races. You have more than enough energy stored. If you are pushing the limits of your glycogen storage through multiple hours of exercise, improving your gut health may be beneficial.

The gut microbiota produces short-chain fatty acids (SCFAs) in the large intestine. These SCFAs may improve glucose uptake and glycogen repletion by increasing the expression of glucose transporter type 4 (GLUT4). SCFAs can also assist with lipid and carb metabolism in the liver and muscle, supporting exercise demands.

Where do these lovely SCFAs come from? The same source is largely responsible for improving your overall gut health.

Fiber Isn’t Just for Glucose Control

So, how do you improve gut health? The easiest way is to eat a lot of whole foods (minimal processing, not the grocery store), particularly those with fiber. You want both soluble and insoluble fiber.

Soluble fiber is water-soluble and forms a gel-like substance in the stomach which slow digestion, helping control blood sugar and cholesterol, like a metabolic sponge. Sources include avocado, oats, peas, beans, apples, citrus fruits, carrots, broccoli, barley.

Insoluble fiber is not water-soluble and passes through the gut, adding bulk to stool and improving regularity. It also helps regulate insulin. Sources include whole wheat flour, bran, nuts, seeds, and the skins of many fruits and vegetables.

We start to see substantial health benefits —lower body fat, improved glycemic response, and reduced blood pressure, triglycerides, and low-density lipoprotein cholesterol (LDL-C) — once crossing the 25–30 gram per day threshold.

Unfortunately, most adults fall woefully short on their daily fiber intake, consuming between 12–18 grams per day in the United States. Europe tends to fair better but the range is large with 16–29 grams per day in Europe. The difference is not surprising as a standard American diet contains more processed foods, which tend to be low in fiber (unless it has been supplemented, but that is often only soluble fiber).

The 30 grams per day volume directly relates to microbiota diversity as well, potentially influencing the exercise mechanisms discussed earlier. Eliminating fiber — such a carnivore diet or extreme caloric restriction — crushes your diversity while increasing fiber intake boosts your diversity. We can see changes in bacterial diversity in as little as 24 hours.

In general, a shift towards higher diversity or richness in gut microbiota is considered healthy.

So, in addition to reducing your risk of chronic non-communicable diseases, such as obesity, cardiovascular disease, type 2 diabetes, and colon cancer, eating sufficient fiber may boost your exercise capacity.

Eat your veggies!

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