Gut health is an increasingly discussed topic these days. With the growing concern for health and wellness, it is important to understand why gut health is so important and how we can improve it. In this article, we will explore some aspects of gut health, from why it is important, how the gut-brain axis can affect our mental and emotional health, to how to improve it through diet and other methods.
Why is gut health important?
The human gut is responsible for several functions that are essential for the proper functioning of the human body. In addition to absorbing nutrients from the food we eat, the gut is home to billions of microorganisms, the great majority of which are beneficial to our health and essential to our well-being and survival. The millions of microorganisms that live in our gastrointestinal tract make up our gut microbiota. Microbiota stimulate the immune system, break down potentially toxic food compounds, and synthesize certain vitamins and amino acids, including the B vitamins and vitamin K.
However, the performance of these functions depends on the quantity and quality of the microbiota, which is influenced by several factors. These include diet, genetics, exposure to antibiotics, type of birth, and breastfeeding. These factors can influence the composition of the gut microbiota and consequently gut health.
Gut health is the state of balance of beneficial and pathogenic microorganisms living in our gut. When there is a predominance of beneficial microorganisms, gut health is considered good. However, when there is a change in the balance of bacteria in the gut, called "dysbiosis", which has been linked to several diseases such as obesity, diabetes mellitus type 2, cardiovascular disease, irritable bowel syndrome, neuropsychiatric diseases, and others.
How does gut health affect mental health?
Gut health can directly and indirectly affect mental health, which means that keeping the gut healthy can have a positive impact on emotional well-being. Communication between the gut and the brain is made through a set of mechanisms that constitutes the "gut-brain axis". The gut-brain axis consists of two-way communication between these two organs, which is done through nerve stimulation and neurotransmitters. Bacteria are thought to communicate directly with the brain through stimulation of the vagus nerve, which runs through the human body from the brain to the abdomen, and indirectly through the production of neurotransmitters (such as dopamine, serotonin, and others) and other microbial metabolites such as short-chain fatty acids (SCFA), while also interacting with our immune and endocrine systems.
Studies show that stress can negatively affect gut health, and vice versa. The increased inflammation that often follows stress and depression can trigger the overgrowth of harmful bacteria, stimulating dysbiosis and "leaky-gut", with increased intestinal permeability. This condition, could in turn allow toxins and bacteria to seep into the bloodstream, leading to a generalized inflammatory response and possibly the production of anxiety-associated hormones such as cortisol.
In addition, studies that have found an association between gut health and depression show that people with depression have a different composition of gut bacteria compared to healthy people. For example, it was observed that individuals with depression had a decrease in beneficial bacteria (Lactobacillus and Bifidobacterium) in their gut. That is why gut is often called the second brain, or gut brain.
Worst foods for intestinal health
Some food choices can negatively affect gut health. Unhealthy dietary habits such as a western diet (characterized by low fruit and vegetable intake and high consumption of animal-derived protein, saturated fats, refined grains, sugar, salt, alcohol, and corn-derived fructose) can lead to the proliferation of harmful bacteria leading to dysbiosis and a leaky gut. Dietary factors with negative effects on the microbiota:
- Western diet (high consumption of ultra-processed foods, fried foods, saturated fat and refined sugar)
- Animal-based protein
- Saturated fatty acids
- Non-nutritive artificial sweeteners
Best foods for intestinal health
Fiber-rich foods, such as fruits, vegetables, legumes, and whole grains, are great for gut health. Dietary fiber can only be broken down and fermented by enzymes from microbiota living in the colon and it causes the production of SCFA that can be used by the body as a source of nutrients, but also plays an important role in muscle function and possibly in the prevention of chronic diseases, including certain cancers and intestinal diseases. In addition, fermented foods, such as yogurt, kimchi, can help promote healthy gut microbiota through the growth of good bacteria. Dietary factors with positive effects on the microbiota:
- Mediterranean diet (Centered around fruits, vegetables, olive oil, nuts, legumes, and whole grains)
- Plant-based diet
- Fruits and vegetables
- Prebiotics and probiotics (If you want to know more about these substances, we have an article about them)
- Plant-based protein
- Healthy fats such as monounsaturated (Found in extra virgin olive oil) and polyunsaturated fatty acids (Found in sunflower, soybean, corn oil, as well as nuts and seeds)
- Polyphenols (bioactive compounds with anti-inflammatory and antioxidant properties, found in foods such as fruits and vegetables, cocoa, spices, nuts, and extra virgin olive oil, as well as beverages such as coffee and green tea)
Recently, the concept of psychobiotics has emerged, describing exogenous factors that influence the microbiota (e.g., via probiotics, prebiotics, diet) with bacterially mediated positive effects on mental health.
Image 1: Best and worst food for gut health and the gut-brain axis
The gut-brain axis is a complex system that is strongly influenced by diet and plays a critical role in maintaining overall health and well-being. And therefore, the way we eat over the long term appears to be the factor that has the most profound impact on the formation of the microbiota and thus the effectiveness of its functions, including impacting brain function and behavior. Beside the diet, other practices that can contribute to gut health are regular exercise, stress reduction, and adequate sleep. All these practices help maintain the balance of the body, including the gut. Thus, maintaining a healthy gut is essential to optimizing the gut-brain axis and promoting well-being.
The Bottom Line
 Berding, K., et al., Diet and the Microbiota–Gut–Brain Axis: Sowing the Seeds of Good Mental Health. Advances in Nutrition, 2021. 12(4): p. 1239-1285.
 Järbrink-Sehgal, E. and A. Andreasson, The gut microbiota and mental health in adults. Current opinion in neurobiology, 2020. 62: p. 102-114.
 Madison, A. and J.K. Kiecolt-Glaser, Stress, depression, diet, and the gut microbiota: human–bacteria interactions at the core of psychoneuroimmunology and nutrition. Current opinion in behavioral sciences, 2019. 28: p. 105-110.
 Mills, S., et al., Precision nutrition and the microbiome, part I: current state of the science. Nutrients, 2019. 11(4): p. 923.
 Appleton, J., The gut-brain axis: Influence of microbiota on mood and mental health. Integrative Medicine: A Clinician's Journal, 2018. 17(4): p. 28.