The gut, specifically the small and large intestines and the complex microbiome that lives within these organs, plays a crucial role in bodily function and human performance. Primarily, the gut is responsible for the digestion and absorption of macro- and micronutrients that support both working and recovering cells, ensuring full support for cognitive and physical performance. (source). Continued research has shown that the gut has a secondary purpose as a supporting organ.
There is increasing interest in the gut’s connection to cognitive function, and for good reason. For starters, roughly 95% of the neurotransmitter serotonin is produced in the gut. (source) This is only the beginning of the bi-directional relationship between the gut and the brain, often referred to as the gut-brain axis. Research suggests that the gut and brain continually communicate through a plethora of neural, endocrine, immune, and humoral pathways. (source)
The gut also plays a crucial role in immunity. The gut’s microbiome has been shown to influence immune cell development, and it houses these cells while acting as a barrier to pathogens. (source, source) Additionally, the gut microbiome, which is composed of trillions of microorganisms, interacts with the immune system, promoting immune regulation and tolerance. (source) This balance helps prevent overreactions, such as allergies and autoimmune diseases, while maintaining the body's ability to defend against infections effectively.
While the gut’s role in nutrient absorption, cognitive function, and immune function are well-established, research continues to find new connections throughout the body. For example, the gut has been shown to affect the cardiovascular system, skeletal muscle performance, and thyroid function. (source, source, source) Though more research is needed in these emerging areas, the gut’s role in optimizing individual systems and overall performance is undeniable.
The gut is an integral component of human health and performance. Not only does it fulfill a primary role of nutrient absorption, but it also connects to almost every other system in the body, either directly or indirectly.
Nutrient absorption is the primary purpose of the gut. Poor gut health has been linked to suboptimal nutrient absorption resulting in malnutrition. (source) Peak performance requires nutrients. For example, amino acids support lean mass and serve as the backbone for many enzymes and hormones. Glucose promotes energy levels, and fats are needed to build lasting energy stores and many hormones. These are just a few of the nutrients absorbed in the gut that power processes throughout the body. Without these nutrients, the body and mind cannot function or recover efficiently. Supporting optimal gut health leads to desired nutrient absorption, which then supports every functioning system in the body.
Cognitive performance relies heavily on gut health optimization. (source) Research has consistently demonstrated the continual communication between the gut and the brain through a variety of pathways. (source) Notably, a recent review suggests that higher gut biodiversity is linked to better cognitive performance and related physiological scores. (source) This interplay between the brain and gut requires full support from both ends. Promoting a healthy gut means promoting better cognitive performance.
A fully functioning immune system would not be complete without the full support of a healthy gut. The gut plays a critical role in the production and development of immune cells, and it acts as a barrier against pathogens. A 2012 review calls attention to the connection between increased gut permeability (also known as “leaky gut”) and susceptibility to various pathogens. (source) Optimal performance requires the ability to effectively and efficiently fight infections. Sick time hinders training time, capacity, and recovery. A healthy gut supports a fully functioning immune system, which ensures less time will be lost due to sickness.
Research on the importance of gut health and its implications for other bodily systems is continually revealing new findings. Above are a few well-established examples of how gut health can have positive effects on systemic health and performance. While more research is needed to fully understand these interactions, the gut’s ability to support the cardiovascular system, skeletal muscle performance, and thyroid function demonstrates its essential role in cognitive and physical performance. (source, source, source)
Common indications of gut health function are included in the table below:
As stated previously, the gut comprises the small and large intestine. Within these organs is an ecosystem that contains billions of both harmful and beneficial microorganisms. Of these organisms, bacteria are often the main focus of discussion. The term “gut health” generally refers to the overall health of the organ system, and, more specifically, to the balance between harmful and helpful microorganisms. As this balance starts to favor harmful microorganisms, the multiple functions of the gut begin to suffer. There are a variety of nutritional, lifestyle and supplemental interventions that can help promote optimal gut health and support peak performance through multiple pathways.
Consume fermented foods: Foods like yogurt, kimchi, and kefir can help promote a healthy gut environment. These foods are rich in probiotics – beneficial bacteria that are crucial for maintaining a healthy balance in the gut microbiome. (source) By promoting the growth of these friendly bacteria in the intestines, fermented foods contribute to better digestion and nutrient absorption, while also supporting the production of short-chain fatty acids that are crucial for the health of intestinal cells and modulation of the immune system. (source) Recommendation: Eat at least one serving of fermented food like fermented vegetables, yogurt, kombucha, or kefir, daily.
Walk in nature: Forest bathing can indirectly support gut health by reducing markers of physiological stress. (source) Stress has been shown to exert negative effects on the gut biome through a combination of stress hormones, inflammation, and autonomic changes. (source) Reducing chronic stress can help mitigate these negative effects and positively affect the functioning of key organs like the stomach and intestines, ultimately promoting a healthy balance of gut bacteria. Recommendation: Spend at least 20 minutes outside, preferably in a natural setting, daily.
Supplement with glutamine: Glutamine can promote gut health by nourishing the intestinal lining, aiding in the repair of damaged tissues, and supporting the growth of healthy gut cells. (source) As a vital amino acid, glutamine plays a crucial role in maintaining the integrity of the gut barrier, which helps to prevent harmful substances from leaking into the bloodstream while also fostering a balanced microbial environment in the intestines, ultimately contributing to overall digestive wellness and gut health. (source) Recommendation: Consume at least two, 5 g servings of glutamine daily.
The gut is a complex system requiring extensive examination to assess overall function. Key biomarkers give a general idea of how efficiently the gut is performing, and they provide insight into the balance between beneficial and harmful microorganisms within the gut environment. An examination of other, associated biomarkers provides additional insight that may be used to pinpoint issues and inform interventions.
Amylase is a digestive enzyme produced in the pancreas that helps break down carbohydrates throughout the digestive process. Though not produced directly in the gut, this biomarker provides insight into how efficiently the gut is accomplishing its primary tasks of nutrient digestion and absorption. Adequate levels of amylase help ensure desired carbohydrate breakdown and absorption.
Lipase is a digestive enzyme that helps break down fat. Although this biomarker is produced in the pancreas, lipase can be found in the gut, and it provides insight into the gut’s performance. By maintaining desired concentrations of lipase, optimal nutrient digestion and absorption can be supported.
GGT, or gamma-glutamyl transferase, is an enzyme that is primarily produced in liver cells. This biomarker gives insight into gut function and microenvironment, as GGT levels have been associated with gallbladder efficiency, alluding to the body’s ability to effectively digest fats. (source) GGT has also been associated with the presence of certain bacterial strains, giving insight into the balance between beneficial and harmful bacteria in the gut microbiome. (source)
Uric Acid is an enzyme produced in multiple areas of the body, including the gut, and is the result of purine metabolism. Bacteria in the gut has been shown to aid in the metabolism of uric acid, helping to control systemic levels. Measuring these levels can give further insight into how efficiently the gut is working. (source)
