The three main causes of death in the United States are heart disease, cancer, and stroke.¹ Rates of obesity and diet-related chronic diseases in the United States are higher than ever. About half of all American adults have one or more chronic diseases that are related to poor quality diet and gut health.² The Western diet consists of highly processed and preserved foods, sterilized of all beneficial probiotics and prebiotics. These foods play a significant role in promoting diet-related diseases and poor gut health.

It’s obvious that consumers need to make healthier life choices when it comes to the quality of their diet and the frequency of their exercise to prevent many types of chronic disease. To understand why diet has such a great impact on our health and what changes we must make, we have to understand our second brain, the gut microbiome.

The Microbiome and the Gut-Brain Axis

In the human gut, there are up to 100 trillion bacteria, their identity determined from the moment of birth. The microbiome develops with age, as environmental stimuli and food are variable. The microbiome consists of over 100 times more genes than the entire human genome!³ It is becoming increasingly clear that these microbes are required for normal brain development as well as brain function in adulthood.

Our gut microbiome is essential for digestion and nutrient absorption from the food we consume. They produce energy that is otherwise inaccessible to us by breaking down soluble fiber. These microbes also produce vitamins such as biotin, folate, and vitamin K, prevent pathogen accumulation, and aid in the development of our immune system.⁴ The gut microbiome composition seems to be more influenced by diet and environmental factors rather than genetic factors which is fortunate since we can’t change our genetics

From “Harnessing the Power of Microbiome Assessment Tools as Part of Neuroprotective Nutrition and Lifestyle Medicine Interventions”. Click here for the full image

The gut-brain axis consists of a bidirectional communication system between the central nervous system and the gastrointestinal tract.⁵ This relationship connects the emotional and cognitive centers of the brain with the functions of the gut. We don’t really understand the complexity of the gut-brain axis system yet but we are able to observe some of its impacts on the overall health of individuals.

This image belongs to Straight From a Scientist. Click here for a mobile-friendly vertical version

An Unhealthy vs. Healthy Microbiome

A healthy microbiome is defined by the diversity and abundance of the native microbes in the gut, which is a state called eubiosis. Whether the abundance of just specific types of microbes or the abundance of all microbes is best for us remains unclear. Considering that these microbes aid in the absorption of nutrients and the establishment of our immune system, it makes sense that a lack of diversity and abundance can result in inflammation. This unhealthy state is termed dysbiosis.

Dysbiosis is a condition related to illnesses such as celiac disease and inflammatory bowel disease, obesity, metabolic disorder, cardiovascular syndrome, allergy, and asthma.⁷

Disruption of the gut microbiome in humans is associated with the development of various diseases and inflammation. Through the gut–brain axis system, the gut microbiome influences neural development, cognitive function, behavior, anxiety, and depression.⁵

Possible Causes of Dysbiosis

• Lack of diversity and quality of foods
• Processed and refined foods
• Use of antibiotics
• Lack of probiotics and prebiotics
• Sanitation
• Clinical practices such as C-sections
• Not breastfeeding (affects the infant)
• Stress
• Environmental toxins

Inflammation is associated with a wide range of disorders, thought to be triggered by an inflammatory immune response from the gut to the brain. Alterations to the gut microbiome have been observed to play a key role in promoting inflammatory bowel conditions which can increase the risk of mental disorders. These conditions are observed to be more prevalent in females than in males, with the highest rates being in the western parts of the world. This then suggests that environmental exposures, diet, and alterations to the gut microbiome have a great influence on inflammatory bowel conditions.⁶

Some interesting findings on this

• Hadza hunter-gatherer individuals were found to possess higher levels of microbial abundance and biodiversity compared to Italian urban controls.⁸
• Stress caused the gut microbiota of lean female mice to more closely resemble that of obese female mice, suggesting microbial changes may depend on sex.⁹
• A study on a large population reported that treatment with a single antibiotic was associated with an increased risk for depression and anxiety, rising with multiple exposures.¹⁰
• Obesity and obesity-related metabolic disorders are characterized by specific alterations in the composition and function of the human gut microbiome.¹¹

How to Maintain a Healthy Microbiome

Prebiotics and Probiotics

Prebiotics are functional foods that are indigestible in the upper gastrointestinal tract that stimulate growth of gut microbes. Studies have shown that pure prebiotics increase beneficial gut bacteria. Galactooligosaccharides are prebiotics that have been shown to promote the growth of beneficial microbes that improve lactose digestion and tolerance in individuals who are lactose intolerant.¹²

Probiotics are live microbes that can benefit the gut by increasing the diversity and abundance of microbes. They are likely to replace pathogenic bacteria and promote a rebalancing of the microbiome to prevent gut inflammation and other diseases.¹³

Fiber

Fibers have been observed to provide substrates for microbial growth, allowing microbial species that are able to utilize these substrates to expand their populations. The average fiber intakes for U.S. children and adults are less than half of the recommended levels.⁸

High intakes of dietary fiber are associated with a lower risk for developing coronary heart disease, stroke, hypertension, diabetes, obesity, and certain gastrointestinal diseases .⁸ Increased fiber intake has been observed to ease certain gastrointestinal disorders and enhance immune function.⁸

Exposure to stress has been shown to alter the profile of the microbiome, reducing diversity and promoting inflammation. Inadequate sleep increases the risk of age-related cognitive decline. Partial sleep deprivation alters the human gut microbiome, and its composition is associated with cognitive flexibility in animal models.¹⁴

Overall, the microbiome remains mysterious to us in many ways but it is evident that it is incredibly crucial to maintain a healthy microbiome to improve our brain function and to increase longevity. By making changes to our diet and managing our sleep and stress, we can reverse the damages done to our gut in order to become healthier individuals. Understanding the microbiome has very promising applications such as developing therapeutics for those suffering from diseases related to dysbiosis.

For a more detailed article on the microbiome, check out the article “The Microbiota-Gut-Brain Axis: What, Why, and How to Maintain Gut and Brain Health” by Straight From a Scientist!

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