In recent years, the world of health and wellness has been a buzz with terms like ‘probiotics’, ‘microbiome’, and ‘gut-brain connection’. Everywhere we turn, from trendy nutrition blogs to advertisements for the latest fermented foods, there’s a growing fascination with gut health. But what’s behind the hype, and why has gut health become a hot topic in the world of science and well-being? That’s what we are going to cover in this article.

WHAT IS THE GUT MICROBIOTA AND HOW DOES IT INFLUENCE OUR HEALTH?

The gut microbiota is the collective term for the array of microorganisms, including bacteria, viruses, archaea, and protozoans, that inhabit the gastrointestinal (GI) tract of a particular person. Recent studies have found connections between the gut microbiome and a wide array of health conditions, including obesity, autoimmune diseases, and mental health disorders. Understanding the composition and function of gut microbiota has the potential to revolutionize healthcare by enabling personalized treatments. The gut microbiota is made up of up to 100 trillion symbiotic microbes (a mutually beneficial relationship between the human and the microbe)!¹ The gut microbiota feeds on food residues that the human body does not digest, mucus secreted by the gut, and dead cells that are shed, which keeps their population levels high.²

The microorganisms living in your gut produce a large number of physiologically active substances, including short-chain fatty acids, vitamins, anti-inflammatory, analgesic (pain-relieving), and antioxidant products, along with neurotoxins, carcinogens (cancer-causing substances), and immunotoxins. These products can enter the bloodstream, directly regulate the expression of genes, and affect the body’s immune and metabolic processes, including energy balance.

The intestinal barrier comprises a layer of epithelial cells that are tightly connected by structures called tight junctions and mucus. It blocks the entry of diverse exterior antigens, including food antigens, bacteria, pathogens, and toxins, while simultaneously absorbing nutrients and acting as a lubricant.²'³ This barrier also provides important components for bacterial growth, adhesion, and protection. The gut microbiota and mucosal barrier have a symbiotic relationship, where the mucosal barrier helps the bacteria thrive, and the gut microbiota contributes to the health of the mucosal barrier.⁴ Tight junctions act like gatekeepers, regulating the passage of substances between the cells. Disturbances in the gut microbiota can cause abnormalities in the membrane by loosening the tight junctions. When these tight junctions become vulnerable, the intestinal barrier is compromised, allowing larger molecules to pass through. This can contribute to dysbiosis and then evolve into 'leaky gut syndrome'.⁵

Furthermore, an imbalance in the microbiota can cause metabolic disorders and increase central appetite, which can lead to diseases like obesity. As a result, the gut microbiota plays a huge role in both healthy and disease states. Therefore, it is important to create a good environment that fosters healthy gut microbiota.² Healthy gut microbiota is considered healthy when it is highly diverse, whereas a microbiome that lacks diversity has been associated with various diseases. ²

In a nutshell, a healthy microbiome is dependent on its ability to be resistant to stress, resilient to external (pharmaceutical, dietary) or internal (age) changes, and the ability of the microbiome to recover after changes like this have affected the microbiome.⁶

FACTORS THAT AFFECT THE GUT MICROBIOTA

The composition of a microbial community depends on the person, but it can be affected by exogenous (outside the body) and endogenous (inside the body) aspects.⁴

EXOGENOUS FACTORS

Your gut microbiota is mostly affected by exogenous factors like diet, lifestyle, stress, medications, alcohol consumption, and environment.⁷

The composition of your microbiota starts when you are a fetus, as microbiota exist in the placenta, amniotic fluid, umbilical cord blood, and meconium. These maternal microorganisms play a role in the establishment of the child’s microbiota.² The GI tract is very quickly colonized after birth, events such as illness, antibiotic treatment, and changes in diet further influence the composition of your gut microbiota. Your gut microbiota composition can also be affected by whether you were delivered vaginally or via Cesarean section (C-section). The microbiota of infants delivered vaginally contains a high abundance of lactobacilli during the first few days, as a result of the high load of lactobacilli in the vaginal flora. The fecal microbiota of vaginally delivered infants has been shown to have a 72% resemblance to their mother’s fecal microbiota, whereas babies delivered by C-section only had a 41% resemblance to their mother’s fecal microbiota.⁸ However, there is a ‘window of opportunity’ in the early life of a child, during which time the composition of the intestinal microbiota can still be ‘re-programmed’ through nutritional interventions such as breastfeeding. The timing and selection of the first solid foods are also factors that have a significant effect on the correct development of the gut microbiota. The length of the ‘window’ period is a matter of debate but is most likely from conception until the age of 2–3 years old.⁹

A prominent aspect that can affect the composition of the community is one’s eating pattern. There is evidence that dysbiosis (an imbalance between good and bad bacteria) can be caused by a Western diet. The Western diet is characterized by high intakes of pre-packaged foods, refined grains, processed meat, high-sugar drinks, candy, salt, fried foods, high-fat dairy products, and high-fructose products. This diet can cause dysbiosis as it allows for the growth of gram-negative bacteria, which increases local inflammation and intestinal permeability. Antibiotics can affect the composition of the gut microbiome as they decrease the diversity of bacteria and can disrupt the balance between the ‘good’ and ‘bad’ bacteria.¹ A course of antibiotics can affect an individual’s gut microbiome differently depending on the type of antibiotics, age, diet, and how many times they have taken antibiotics in the past. However, even a single use of antibiotics can result in dysbiosis.¹

ENDOGENOUS FACTORS

Our genetic makeup influences our gut microbiota as it can affect aspects of our physiology and immune response that then impact the conditions available for microbial colonization.¹⁰ For example, genes can influence the production of mucus in the gut lining, and variations in genes related to mucus production can affect the ability of certain gut microbiota to establish and maintain a stable community, affecting the composition of the microbiome. However, environmental factors have a more significant impact on the composition of the microbiome. The percentage of microbiome heritability is estimated to be below 2%, whereas more than 20% of the variation is related to diet and drugs among other factors.²