The gut microbiome heavily influences many bodily functions and plays a role in the development of certain diseases.
Its influence has been studied, especially in the fields of weight regulation, metabolic syndrome and psychiatric diseases.
Substances that support the optimal composition of the gut microbiome can be found in a normal, balanced diet, although supplementation with probiotics is also an option.
What is the microbiome?
The microbiome is the collective name for all microorganisms that inhabit a particular environment/region. It is an essential part of the human body, and recent research even confirms that microorganisms are present in the human body in equal or even greater numbers than the body cells themselves. These small living organisms can be found in the mouth, on the skin and on the nose — certainly, the most well‑known and diverse representative is the gut microbiome.
This microbiome not only influences overall health and many bodily functions (see below) but also acts as a kind of ecosystem in which certain strains of bacteria support each other's growth or, conversely, crowd out pathogenic (harmful) species. Although the conclusions of studies vary slightly in absolute numbers, research at the molecular level speaks of about 1000‑1500 possible species of bacteria in the gut microbiome, possibly as many as 3000. Some studies also suggest that a person has an average of about 160 species of bacteria in their microbiome, but this number can vary considerably depending on the factors that influence microbiome diversity.
What determines the composition and diversity of the gut microbiome?
1. Type of birth and nutrition during infancy
During a natural birth, the baby encounters bacteria in the mother's birth canal, which then influences the composition of the gut microbiome and stimulates the function of white blood cells and general immunity. In babies born by caesarean section, the bacterial colonisation of the gut is different, and a relatively large number of studies have highlighted an increased risk of overweight, obesity or diabetes in these babies. It should be noted, however, that there are also studies describing the situation in quite the opposite way. Many other factors also enter into this relationship, such as the sex of the newborn or the weight of the mother. Definitive confirmation will, therefore, have to wait.
The situation is very similar regarding nutrition after birth. Breast milk naturally contains bacteria that shape the composition of the baby's microbiome. The spectrum of these bacteria in breast milk is estimated at more than 700 species, and it is very interesting to note that the strains differ between normal‑weight and obese mothers, as well as between mothers who have given birth naturally or by caesarean section. Last but not least, the bacteria present in breast milk also change over time (changes have been observed, for example, when comparing the first and sixth months of breastfeeding). In addition to these bacteria from breast milk, the baby also encounters bacteria living on the mother's skin, which again broadens the spectrum of bacterial colonisation of its gut. This suggests that breastfeeding is the best way for the baby to develop an optimal gut microbiome composition. However, some modern breast milk substitutes are also enriched with some strains of probiotics.
2. Genetics
Although this area is still very under‑researched, it appears that family members share more traits describing gut microbiome composition than "strangers", and that the similarity is higher in identical than in fraternal twins. This suggests that genetics will also have some influence in this area, although diet and lifestyle are thought to have the greatest effects.
3. Infection
Viral, but especially bacterial infections, can lead to gut dysbiosis, i.e., a significant disruption in the composition and biodiversity of the microbiome, as well as in the total number of bacteria colonising the gut. It has also been shown that transplantation of gut bacteria from healthy donors can help treat some intestinal diseases, as well as diseases outside the digestive tract. Faecal transplantation can take place through a nasojejunal probe, endoscopically via the rectum or also in the form of swallowing tablets containing the desired material (i.e., a modified faecal concentrate from a donor).
4. Drugs
It's widely known that antibiotics can really mess with the composition of the microbiome and the lifespan of the bacteria. In some cases, the negative impact can even be permanent. However, in addition to the well‑known antibiotics, other drugs such as metformin, which is used as an antidiabetic agent in the treatment of type 2 diabetes, could also have a possible negative effect. Still, the results of the studies are not clear‑cut, so further high‑quality research is needed.
5. Diet
As already mentioned, studies nowadays attribute the highest influence on the composition of the microbiome to diet and lifestyle. Sudden changes in dietary composition lead to relatively rapid fluctuations in the composition of the gut microbiota, with negative effects particularly evident when consuming diets high in animal fat and low in fibre. However, even in this respect, a higher number of good‑quality studies is needed for an accurate understanding.
The gut microbiome and its impact on health
Can the gut microbiome promote weight loss?
Studies in mice and humans show that the composition of the gut microbiome is associated with, among other things, a predisposition to overweight or obesity. Individuals with excess weight tend to have a higher Firmicutes‑to‑Bacteroidetes ratio in their gut microbiome. These individuals gain more energy from their diet than their normal‑weight counterparts. According to studies, people with low gut microbiome diversity are also more susceptible to inflammatory diseases. Even more interestingly, in research involving six weeks of eating a reduced‑energy diet, overweight people showed positive changes in microbiome composition.
Probiotics in support of metabolic syndrome therapy
Metabolic syndrome includes reduced insulin sensitivity leading to type 2 diabetes, increased blood pressure and dyslipidaemia.
Research has shown that supplementation with certain selected strains of bacteria, in particular Akkermansia muciniphila, has a positive effect on insulin sensitivity, blood lipid ratios and levels, and weight loss in people with metabolic syndrome. These findings confirm that the gut microbiome extends beyond the gastrointestinal tract and could be a supportive treatment for many diseases in the future.
Linking the microbiome to the psyche
There is evidence that the gut and the brain are linked by a two‑way communication pathway that can be disrupted, for example, in intestinal inflammation or just microbial dysbiosis. The bacterial composition of the gut can literally influence the release of neurocirculatory hormones or neurotransmitters in the brain, which can, among other things, have a positive effect on cognitive function, but also regulate the risk of developing anxiety or depression. Current evidence also suggests that certain strains of bacteria are suitable for supporting the treatment of certain psychiatric conditions.
- Learn more: Psychobiotics for Mental Health
Intestinal dysbiosis
Gut dysbiosis describes a condition where there are changes in the composition or function of the gut microbiome. Most commonly, this involves a reduction in the diversity of gut bacteria, a reduction in the number of beneficial bacteria or, conversely, an excess of pathogenic bacteria. As mentioned above, intestinal dysbiosis can be based on genetic background or early childhood, but factors such as diet, lifestyle, disease or hygiene are even more important. Intestinal dysbiosis can result not only in a disruption of the intestinal barrier but also in negative changes in a person's immune system and overall metabolism.
How to improve your gut microbiome?
Whether you've had an infectious disease, are taking antibiotics or simply feel that your digestion isn't working quite as it should, gut dysbiosis may be one of the causes. Clinically, probiotics, in particular, are used to increase the number of beneficial bacteria in the microbiome and reduce the growth of 'harmful' bacteria. In some more severe cases, the aforementioned faecal transplantation may also be appropriate. And if you want to keep your microbiome in good balance for the long term, we recommend addressing the points below.
What to do to support your gut microbiome?
1. A balanced diet with plenty of fibre and probiotics
Fermented dairy products
It is widely known that fermented dairy products are a natural source of probiotics. They also contain good‑quality protein, vitamin D, and calcium, which are important for bone health. In terms of their positive effect on the gut microbiome, products such as kefir, acidophilus milk, or yoghurt are the best choices.
Fermented and pickled vegetables
Fermented vegetables mainly contain lactic acid bacteria, but you will also find probiotic fibre, which serves as a food source for the beneficial bacterial strains. The only thing to watch out for is the possible salt content, which can add up with regular consumption.
Fruit, vegetables and whole grain cereals
Fruits, vegetables and whole grains are sources of fibre, which is great for your digestive tract and the bacteria themselves. Increased consumption of these foods has been shown to promote growth, especially in Lactobacillus and Bifidobacterium strains.
Fermented legumes
If you like to experiment, you can spice up your diet with fermented legumes, which are a staple of Asian cuisine in particular. These are products such as miso or natto. Thanks to fermentation, these products are a natural source of beneficial bacteria.
- Learn more: The 8 Best Probiotic Foods
Another option, of course, is supplementation in the form of probiotic supplements, where one can be assured of guaranteed amounts and strains of bacteria.
What should you watch out for?
Studies show that excess intake of certain foods or substances can also affect the gut microbiome negatively. These include excessive amounts of sugar, alcohol and animal fats.
2. Stress management
Chronic stress interferes with many of the body's systems, and the gut microbiome is no different. Through increased concentrations of stress hormones or the induction of inflammatory processes, excess stress can also affect the composition of the gut microbiome, and not in a positive way.
3. Quality sleep
Sleep is another non‑negligible factor that influences all spectrums of human health, mental well‑being, and sports and work performance. In the context of the gut microbiome, sleep quality and duration have been shown to have a major impact on sleep composition.
- Learn more: 9 Tips on How to Improve Sleep Quality
4. Get moving
Movement has countless benefits for the body, but did you know it also affects the gut microbiome? According to a 2023 review, eight weeks of moderate to high‑intensity physical activity induces positive changes in this area, both in healthy people and those suffering from digestive tract issues.
What to take from this?
The human body contains millions of bacteria, with the gut microbiome being the most densely populated. Its composition affects many bodily functions as well as the prevention/development of certain diseases. However, this relationship also works in reverse, with some drugs, diseases and especially diet and lifestyle dramatically affecting its composition.
