We all carry trillions of bacteria within our gut and these microbial companions do all kind of things for us. They help maintain our gut health, they help our immune system to develop, and recent data show that our bacterial companions can affect metabolic diseases, such as type 2 diabetes and obesity.
What is gut microbiome?
The gut microbiota is gradually revealing its secrets. We now know that its ecosystem contains about 1000 different species of micro-organisms, which encode more genes than the human host. The microbiome is the collective genomes of the microbiota. These numerous genes interact with the human host through specific receptors located in the gut’s epithelial, neural and immune cells, as well as through the production of hormones and metabolites. The microbiome is diverse and represents 3 domains of life : Microbes, Fungi, Archea.
Recent studies showed that gut microbiota can influence the metabolism, comparable in influence to a new organ in the body and offering the possibility of a new route for therapeutic intervention. This impact can be either beneficial or detrimental, depending on the relative identity and abundance of constituent bacterial populations.
The gut microbiota impact on health and diseases
The human microbiome intervenes in particular in:
- modulation of bone-mass density,
- promotion of fat storage and angiogenesis,
- development and training of the immune system,
- biosynthesis of vitamins and amino-acids,
- resistance to pathogens,
- modification of the nervous system,
- appetite regulation…
And these are the only known functions today. Researchers begin to elucidate the enormous scientific and therapeutic potential of the human microbiome in almost all medical fields. For example, they are starting to understand how our gut affects our emotional health. Research suggest that the communication between gut microbiota and the brain can be influenced by the intake of probiotics, which may reduce the level of anxiety and depression, and affect brain activity that controls emotions and sensations. Bacteria in the gut can produce various neurotransmitters and these can reach the brain when the intestinal barrier is damaged.
Gut microbiota have also become a focus for research at the intersection of diet and metabolic health. It is widely accepted that obesity and associated metabolic diseases, including type 2 diabetes, are intimately linked to the diet. However, a body of knowledge highlighted the role of the gut microbiota as a mediator of dietary impact on the host metabolic status.
Dysbiosis and altered gut microbiota
There is growing evidence that dysbiosis or microbial disbalance of the gut microbiota is associated with the pathogenesis of both intestinal and extra-intestinal disorders. Intestinal disorders include inflammatory bowel disease, irritable bowel syndrome (IBS), and coeliac disease, while extra-intestinal disorders include allergy, asthma, metabolic syndrome, cardiovascular disease, and obesity. Specifically, patients with type 2 diabetes have reported alterations in the composition and function of their gut microbiota. This suggests a microbe-mediated mechanism of disease.
How to improve gut microbiota? The key effect of diet
Three major elements of modern lifestyles have the strongest impact on the human-microbe symbiosis: nutrition, environmental exposures to chemicals and drugs, and conditions surrounding birth (prenatal events, delivery methods, feeding, infant care environment). From in utero variations to those that rapidly occur postpartum, our gut microbiome changes with age, environment, stress, diet, and health status as well as medication exposure (like antibiotics) or even geography. The changing of our gut microbiota across the lifespan is particularly important. Probably the one thing we do that most affects our gut microbiota is what we eat.
Dietary patterns (vegetarian diets, for example), specific nutrients and bioactive dietary components are all playing significant roles in shaping the gut microbiome. A balanced diet and a healthy lifestyle can contribute to correct or prevent dysbiosis. On a day-to-day basis, what we eat is without a doubt interacting with our microbial friends. So there is a great interest to explore how our diet habits can help us to positively impact our health and prevent dysbiosis modulating the composition of the gut microbiota. More and more studies suggest that a high-fat diet can lead to intestinal dysbiosis which contributes in a loss of gut permeability and activates immune cells that promote inflammation. Research also shows that an unbalanced diet, including a lack of fiber, could have detrimental effects on health through the gut microbiota.
Fermented milk, such as yogurt, delivers a lot of lactic acid bacteria to the gastrointestinal tract and will, at least temporarily, bolster the living microbes transiting through the gut, and that is likely a good thing. According to researchers, they may modify the intestinal environment, improve gut permeability and decrease potentially harmful enzymes produced by the resident bacteria. Other fermented foods like kombucha, sauerkraut, kimchi, are important for replenishing your good gut bacteria. Healthy fats like coconut oil, avocado, olives, butter, fatty fish (like salmon), and healing bone broth are important for calming inflammation that has occurred as a result of having a leaky gut.
A lot of research is currently exploring dietary options that may be valuable for a healthy gut microbiota. In this respect, the consumption of probiotics, as well as prebiotics, draw a lot of attention.
Gut health and probiotics
The relationship between probiotics and gut health is more and more documented. Probiotics, defined by the World Health Organization (WHO), are “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.” You can find them in yogurt for example but also in other probiotic preparations, such as capsules or drinks. Probiotics should not be confused with prebiotics, which are “selectively fermented ingredients that allow specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host well-being and health.” Probiotics provide a way to deliver beneficial bacteria directly to the gut. Much clinical evidence indicates that probiotics and/or prebiotics can be used as a natural intervention to alleviate many of gut disorders.
Recent studies recommend the intake of probiotics, prebiotics or fermented dairy products as treatment or prevention for the described disorders. The living microorganisms in yogurt, in particular Lactobacillus and Bifidobacterium, positively influence disorders such as IBS, infectious diarrhea, allergic disease and necrotizing enterocolitis. Clinical studies confirm the healthy benefits of yogurt consumption, as a source of host-friendly bacteria. Yogurt consumption has been associated with reduced risks of type 2 diabetes, metabolic syndrome, and heart disease, as well as improved weight management. By providing several key nutrients, yogurt is characterized by its live microorganisms added specifically for their probiotic properties. The dairy matrix also matters and most probiotics do just fine in this matrix.
Taking care of the gut microbiota through diet appears to be an obvious strategy to preserve our health status. In this perspective, the consumption of probiotics and fermented foods is studied as a means to positively impact the gut microbiota and therefore prevent dysbiosis or any other dysfunction. Efforts are now focusing on the establishment of causal relationships between diet, gut microbiota and health in people but also on the prospect of therapeutic interventions, such as personalized nutrition.