Why Is Fiber Important for Athletes? The Gut-Muscle Axis and Green Banana Flour

When it comes to sports nutrition, protein and carbohydrates are usually the first things that come to mind. Protein sources, carbohydrates, and fluid intake all play an important role in muscle development, exercise performance, and recovery. However, there is another important component of a balanced diet: dietary fiber.

For many years, fiber has mainly been associated with the digestive system and regular bowel function. However, recent research has also drawn attention to the relationship between the gut microbiota and muscle health. This relationship is referred to in the scientific literature as the “gut-muscle axis.”

So, how are gut health and muscle health connected? Why is fiber important for athletes, and where can green banana flour fit into this dietary pattern?

What Is the Gut-Muscle Axis?

Trillions of microorganisms live in our intestines, and the way we eat can influence the composition of this microbial community.

In particular, certain carbohydrates that can be fermented by the gut microbiota may reach the large intestine without being completely digested in the small intestine. There, they can be fermented by gut bacteria and contribute to the production of short-chain fatty acids (SCFAs).

Acetate, propionate, and butyrate are among the main short-chain fatty acids. These compounds are thought to be associated with the intestinal barrier, energy metabolism, and inflammatory processes.

For this reason, communication between the gut microbiota and muscle tissue has become an increasingly researched topic in sports nutrition.

How Is Fiber Intake Related to Muscle Health?

A UK Biobank study evaluating data from approximately 46,000 people examined the relationship between lifestyle and dietary factors and muscle health. The study reported that regular physical activity and higher dietary fiber intake were associated with the preservation of muscle mass and muscle strength.

These findings do not mean that fiber intake alone determines muscle development. However, they highlight that, alongside regular exercise, adequate protein intake, and a balanced diet, fiber consumption should also be considered in relation to muscle health.

How Do Gut Bacteria Use Fiber?

Some types of fiber we consume reach the large intestine without being completely digested in the small intestine. There, they can be fermented by gut bacteria.

This fermentation process can result in the production of short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate.

These compounds may contribute to:

• supporting the normal function of the intestinal barrier,
• the metabolic activity of the gut microbiota,
• processes associated with energy metabolism.

Butyrate, in particular, is an important short-chain fatty acid used by cells in the intestine. For this reason, consuming sufficient and diverse sources of fiber is important not only for digestive health but also for nourishing the gut microbiota.

Why Is Fiber Important in High-Protein Diets?

While a great deal of attention is given to athletes’ protein requirements and protein intake, the fiber content of high-protein diets should not be overlooked.

When the diet does not contain sufficient amounts of fermentable carbohydrates, gut bacteria may ferment more protein, leading to a process known as proteolytic fermentation. Various metabolites, including ammonia, amines, and p-cresol, can be produced during this process.

For this reason, individuals who consume high amounts of protein should focus not only on protein quantity but also on ensuring that their diet is balanced in terms of fiber, carbohydrates, fats, vitamins, and minerals.

In other words, protein and fiber are not alternatives to one another in sports nutrition. Both have different roles within a balanced dietary pattern.

How Much Fiber Should Athletes Consume Per Day?

For athletes and physically active individuals, some sources recommend consuming at least 30 grams of fiber per day.

However, increasing daily fiber intake dramatically and all at once may not be the best approach. Especially for individuals whose current diets are low in fiber, suddenly increasing fiber intake may cause gas, bloating, and abdominal discomfort.

Increase Fiber Gradually

For example, someone consuming approximately 15 grams of fiber per day may experience digestive discomfort if they suddenly increase their intake to 30 grams.

For this reason, it is recommended that fiber intake be increased gradually over a period of 4–6 weeks. Drinking enough water while increasing fiber consumption is also important.

Pay Attention to Fiber Intake Before Exercise

Because fiber can slow digestion, the timing of its consumption may also be important.

In the 1–2 hours before exercise and on competition days, lower-fiber, easily digestible carbohydrate sources may be preferred to reduce the likelihood of digestive discomfort.

During the first 30 minutes to 2 hours after exercise, rapidly digestible carbohydrates and protein are often preferred to support the replenishment of muscle glycogen stores and recovery.

Fiber-rich foods can instead be distributed throughout other main meals of the day, such as breakfast, lunch, and dinner.

How Can Green Banana Flour Be Used in Sports Nutrition?

It is important to benefit from a variety of food sources to meet daily fiber targets. Green banana flour is one option that can be considered in sports nutrition due to its high fiber and resistant starch content.

One of the notable characteristics of green banana flour is that it contains 47.31 g of resistant starch per 100 g.

Resistant starch is a type of starch that is not completely digested in the small intestine and can reach the large intestine. There, it can be fermented by gut bacteria and contribute to the production of short-chain fatty acids.

Because of this characteristic, resistant starch is among the components attracting interest in research on the gut microbiota and the gut-muscle axis.

The high resistant starch content of green banana flour also makes it an option worth considering for athletes who want to add resistant starch and fiber to their daily diet.

Green Banana Flour Contains Potassium and Magnesium

In addition to protein and carbohydrates, adequate intake of minerals such as potassium and magnesium is also important in sports nutrition.

Green banana flour contains 1,581.28 mg of potassium and 146.96 mg of magnesium per 100 g. When compared with the daily reference intake values established for adults, 100 grams of green banana flour provides approximately 79% of the daily reference value for potassium and 39% for magnesium.

Potassium and magnesium are minerals that play a role in normal muscle function and the normal functioning of the nervous system.

For this reason, green banana flour can be considered an option that may contribute not only to fiber and resistant starch intake but also to the intake of these minerals as part of a balanced daily diet.

Fiber in Sports Nutrition: What Should We Know?

Sports nutrition is not only about protein and carbohydrates. Dietary fiber and the gut microbiota are among the topics receiving increasing attention in research related to athlete health and performance.

With 11.50 g of dietary fiber per 100 g and 47.31 g of resistant starch per 100 g, green banana flour is a noteworthy food option in this context.

However, the key is not to focus on a single product or food, but to establish a balanced dietary pattern that includes adequate amounts of protein, carbohydrates, fats, fiber, vitamins, and minerals.

Green banana flour can be considered one alternative that may contribute particularly to fiber and resistant starch intake as part of this balanced dietary pattern.

References

Morwani-Mangnani, J., Rodriguez-Girondo, M., Singh-Povel, C., Verlaan, S., Beekman, M., & Slagboom, P. E. (2024). Physical activity and fiber intake beneficial for muscle mass and strength preservation during aging: A comprehensive cross-sectional study in the UK biobank cohort. Experimental Gerontology, 193, Article 112474. DOI: 10.1016/j.exger.2024.112474

Cheng, G., Zhang, Z., Shi, Z., & Qiu, Y. (2025). An investigation into how the timing of nutritional supplements affects the recovery from post-exercise fatigue: a systematic review and meta-analysis. Frontiers in Nutrition, 12, Article 1567438. DOI: 10.3389/fnut.2025.1567438

Mancin, L., Burke, L. M., & Rollo, I. (2025). Fibre: The forgotten carbohydrate in sports nutrition recommendations. Sports Medicine, 55, 1067–1083. DOI: 10.1007/s40279-024-02167-1