Gut flora is a collective name for bacteria and other microorganisms that are naturally found in the gut. The bacterial flora is considered to consist of between 300–1000 different species, but the largest part, about 99%, consists of about 30–40 species. 1 Which composition one has depends on a number of factors. For example, it plays a big role how you are born, i.e. if you are born via vaginal birth or by caesarean section, how you eat, pH value in the gut, if you have taken antibiotic courses, etc.
It is usually said that some of the flora is more permanent and some is temporary and dynamic. This means that part of the intestinal flora, which is formed early in life, remains as it is, while part can be influenced with the help of, for example, a healthy lifestyle. Our intestinal bacteria are so numerous that you can say that we are actually more bacteria than human because we have more bacteria than human cells in our body! It is therefore not surprising that they have a very large part in our well-being and that they affect us in many different ways, both good and bad.
Improves nutrient absorption
The primary nutrient absorption takes place in the stomach and small intestine, but some is also absorbed in the large intestine thanks to our intestinal bacteria. About 85% of carbohydrates, 65–95% of protein and all fat are absorbed before reaching the colon. Hard-to-digest carbohydrates and proteins go on to the large intestine and correspond to between 10%-30% of the total energy intake! Without the bacteria, these carbohydrates and proteins would instead leave the body via the feces without further absorption due to the colon's limited digestive capacity. 2 When broken down, or fermented, in the large intestine, the short-chain fatty acids acetic acid, butyric acid and propionic acid are formed, among other things. These are important for maintaining intestinal homeostasis (balance). They also act as fuel for the intestinal epithelial cells and strengthen the intestinal barrier. In addition, the short-chain fatty acids are involved in the communication between the gut and the brain, the so-called "gut-brain-axis".
Vitamin production
Several types of bacteria that are very common in our intestines also have the ability to produce vitamins for us! The bacteria can produce almost all B vitamins, evenB12 . They also produce vitamin K2 . It has not been fully mapped how efficiently these vitamins are absorbed by the body as they cannot be absorbed via the small intestine, which is otherwise the place where vitamins are absorbed. The small intestine sits before the large intestine. However, it has been seen that the vitamins produced by the intestinal bacteria can actually be taken up in the colon via other mechanisms and that they are also used by the bacteria themselves. 3
The connection to the immune system
You've probably heard the phrase "the immune system is in the gut", and it's actually true. Between 70–80% of the cells of the immune system are found in the intestine. It is also the case that the intestinal mucosa protects us against pathogens that otherwise risk getting further into the body. It is therefore important to have a healthy intestine so that the mucous membrane stays tight and does not start to leak through disease-causing bacteria and viruses. Intestinal bacteria are sometimes also called "the immune system's personal trainer" as they help the body's immune cells distinguish between which microorganisms are dangerous and which are harmless to us.
We have many different types of bacteria in the gut, some good and some not. Which composition you have depends on how you live, i.e. what you eat, how much you stress, but part of the intestinal flora is already formed at birth. There are several ways to influence your intestinal flora, which in turn affects your immune system. Adding good bacteria in the form of various lactic acid-forming bacteria is a simple way, these are also called probiotics. They are found in, for example, dietary supplements, certain types of yogurt, pickled vegetables, and other fermented foods.
Lactic acid bacteria
There are many different groups of good gut bacteria, one known group is lactic acid bacteria . Lactic acid bacteria got their name because they produce lactic acid when they ferment. They live by breaking down sugars into lactic acid and act as protection against other bacteria. They also help to increase the amount of other good bacteria in the gut. The fact that they are called "lactic acid bacteria" does not mean that they contain milk or that people who cannot tolerate milk or lactose cannot eat them. There is thus no connection to cow's milk, but only to the substance lactic acid. Two of the most common lactic acid bacteria families are lactobacilli and bifidobacteria.
The balance between good and harmful bacteria
In the large intestine, there are up to 1.5 kg of bacteria in a blissful mixture of species. Some are good and health-promoting and some are less good and downright harmful to health. To feel good, we need a balance between these. You get that by eating a varied, healthy and fiber-rich diet, reducing stress in your everyday life and exercising regularly. A good complement to these habits is to add good bacteria via food supplements. Processed food, sugar and alcohol are examples of foods that feed the less good bacteria and that negatively affect the intestinal flora, which can create an imbalance.
Where are good bacteria in the diet?
Examples of foods rich in lactic acid bacteria are lactic acid vegetables such as sauerkraut and kimchi, some types of yogurt, some types of yogurt, kombucha (fermented tea), sourdough bread, miso soup and tempeh (fermented soybean product). If you want to add a larger dose of good bacteria, a high-quality food supplement is a simple alternative. Today, there are many well-documented strains to choose from, and a mixture of bacterial strains is often found in dietary supplements to provide a wide variety.
Prebiotics
It is also very important to feed your good gut bacteria with fiber that makes them thrive and feel good. These fibers are called prebiotics or prebiotic fibers and are found in, among other things, fruit, berries, vegetables, legumes and whole grain products. Boiled, cold potatoes are also great as they are rich in resistant starch which the bacteria like.
Production of serotonin and dopamine takes place in the gut
The intestinal bacteria affect many parts of the body, including our brain. In connection with the bacteria eating the prebiotic fibers I mentioned above, signaling substances such as serotonin and dopamine are formed. Serotonin is a substance that regulates worry, anxiety, sleep, alertness, pain experiences, intestinal motility and even feelings of satiety and hunger. You may know that serotonin is in the brain, but did you know that between 80-90% of all the body's serotonin is produced in the gut? Dopamine is a neurotransmitter strongly linked to the brain's reward system and is the substance that gives us the feeling of getting a "kick". About 50% of the body's dopamine is formed in the intestine. There is still much to discover regarding the importance of the gut for health, but the researchers seem to agree that it plays a major role.
Sources:
- https://web.archive.org/web/20140512214805/http://www.godamagbakterier.se/probiotika?gclid=CJvs1J6Umr4CFULecgodTQQAiA
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601187/
- https://www.frontiersin.org/articles/10.3389/fnut.2019.00048/full
