In recent years, the term microbiome has come up again and again in connection with nutrition and chronic diseases. But what exactly is the microbiome? What do you know about it? “Something to do with gut flora?”- That’s right. Or have you heard something about it every now and then, but you don’t really have a clear overview? Then look forward to our fact check “What is the microbiome?”. After that, hopefully, you’ll know everything interesting about it!
What is the microbiome - the gut flora?
Not quite. The human microbiome is actually the entire genome of the bacteria, viruses, and fungi that live on the human body. Although the microorganisms colonize the entire body - from the skin or mouth to the lungs - they prefer to live in the gut. About 99% of the microbiome is located here [1]. By the way, the microbiome is the genome of the microorganisms. When we talk about organisms, the term microbiota is more accurate. The term gut flora is now outdated, but firmly established in common usage as a synonym for the gut microbiome.
Does the microbiome weigh 2 kilos?
That’s not true. For a long time, the assumption circulated that the microbiome made up 1-2 kilos of body weight. This figure is untenable; it probably comes from the fact that the amount of microorganisms was also overestimated for a long time. In fact, the microbiome only weighs about 500g, probably even less [1].
Are there 10x more bacterial cells than body cells?
That’s not true. A woman weighing 60 kg has an estimated average of 28 trillion body cells. The rumor stubbornly persists that there are about 10x as many microorganisms living in the gut. But that’s not true. In fact, the amount is approximately the same, and we are talking about 39 trillion microorganisms living in and on us. However, in our opinion, that is no less impressive, is it?
For a long time, the number of bacteria in stool was also overestimated; 1 trillion cells, 10 to the power of 12 cells, were assumed. In fact, there are “only” - absurd in connection with the number that comes now - somewhere between 10-100 billion colony-forming units (CFUs) of bacteria per gram of stool [1,2].
We are speechless at these numbers.
What is the microbiome? In any case, gigantic!
Are there particularly many Firmicutes in the microbiome in obesity?
True - at least for rodents. In humans, it has not yet been conclusively proven that an exceptionally high proportion of Firmicutes leads to obesity. The idea is that Firmicutes make more energy available from food than Bacteroides. This is referred to as the Firmicutes-Bacteroides ratio. People with more Firmicutes would therefore take in more calories with a meal. This could be shown quite convincingly in some comparative studies. Nevertheless, other studies speak against this or find no certain connection [3].
In fact, overall, it has been difficult so far to attribute a specific distribution pattern of microorganisms to the development of concrete diseases. There are too many different strains and, above all, factors such as BMI, gender, lifestyle, or the intake of medications that can influence diseases. These statements stubbornly persist, because how wonderful it would be to predict or prevent diseases in this way. But the research reality is different.
However, it is clear that dysbiosis with reduced diversity of bacterial strains, a high number of facultative anaerobic bacteria, as well as inflammation in the gut, are associated with the development of diseases [2]. The health of the microbiome and the gut should therefore be a top priority for us.
PMS - Is the microbiome to blame?
True - at least partly to blame! Relevant PMS symptoms are depressive moods or anxiety, increased appetite, and sleep disturbances. And what substances can the microbiota produce? That’s right: serotonin, dopamine, and norepinephrine, which significantly influence mood, as well as GABA, which is associated with irritability and anxiety. The microbiome can also produce hormones and substances responsible for appetite and sleep, including leptin, neuropeptide Y, galanin, ghrelin, and orexin. So a dysbiosis in the microbiome can certainly contribute to these symptoms.
And how does dysbiosis occur? Both estrogen and progesterone influence the microbiome. Estrogens increase the production of pro-inflammatory substances, leading to an imbalance of the microbiota and, in addition, to increased permeability of the intestinal wall. Estrogen dominance and PMS are very closely linked.
Some studies found a reduced number of strains that promote anti-inflammatory and antioxidant substances in people with PMS. In addition, the microbiome again produces beta-glucuronidase, which converts estrogens into their active form. The activity of beta-glucuronidase is associated with an increased risk of PMS. These observations are reinforced by the finding that taking antibiotics reduces estrogen levels [4].
Does the microbiome influence mood?
That is true to some extent - but a lot more research is needed here. One thing is clear: there is a gut-brain axis, i.e., the processes in the gut and the brain are closely connected. In the gut is even the so-called “gut brain,” the enteric nervous system. This can influence processes in our body and even the brain independently of the brain. Over 90% of all serotonin is produced in the gut, partly by the microorganisms themselves. Although this serotonin cannot cross the blood-brain barrier, it can influence the central nervous system via the enteric nervous system.
In addition, the microbiota produces enzymes that regulate the breakdown of the amino acid tryptophan into, among others, serotonin. If an imbalance occurs in the microbiome, this can on the one hand influence the concentration of serotonin in the brain and on the other hand inhibit the release of neurotransmitters in the brain, which in turn are responsible for our mood and mental health. In addition, it can lead to inflammation in the nerve tissue and to a change in the permeability of the blood-brain barrier.
Probiotics are useful for a healthy microbiome
True! But it depends on which strains are in the probiotic! To reduce inflammation, Lactobacillus and Bifidobacterium should definitely be included. Inflammation appears to be an important factor in the development of mental health issues. The two species can also reduce the permeability of the intestinal wall and thus improve leaky gut and its consequences. Probiotics can regulate your blood lipid levels.
Current research shows that long-term intake (at least one month) of probiotics has positive effects on physical and mental health. In rats, it could even reduce stress and depression. Lactobacillus rhamnosus was particularly important here. Also interesting: In mice with depression and anxiety, researchers found a reduction of lactobacilli in the microbiome plus an increase in inflammatory markers. The administration of probiotics could increase the number of lactobacilli, improve inflammatory values, and reduce the symptoms in the mice.
Lactobacillus and Bifidobacterium acidify the environment in the gut. This is particularly liked by health-promoting bacteria. This strengthens a healthy microbiome. In addition, probiotics have been shown in studies to be helpful for, among others, lactose intolerance, diarrheal diseases, intestinal ulcers, and strengthening the immune system [5].
It is helpful to take your probiotic together with a prebiotic supplement, thus providing the microorganisms with the fiber they use for their nutrition at the same time [6].
