July 2, 2020

Why gut flora is crucial for your health

Warum die Darmflora für Deine Gesundheit entscheidend ist

Trillions of bacteria, viruses and fungi live in your body. These are known as the microbiome. While some bacteria are associated with disease, others are extremely important for your immune system, your heart, your weight and many other aspects of health.

This article will take a closer look at the gut microbiome, also known as gut flora, and explain why it is so important for your health.

What is gut flora?

Bacteria, viruses, fungi and other microscopic living things are called microorganisms or microbes. Billions of these microbes live in your gut and on your skin. Most of the microbes in your gut are found in a "pocket" of the large intestine, better known as the cecum. The sum of these microbes is called the gut flora.

Although many different microbes live in your gut, the bacteria living there have been the best studied so far. In fact, there are more bacterial cells in your body than there are human body cells. Your body consists of roughly 30 quadrillion cells, but is home to roughly 40 quadrillion bacteria. In other words, this means that you are more bacteria than human (1, 2).

The human gut flora consists of up to 1,000 different species of bacteria and each of these species plays a different role in your body. Most of these bacteria are extremely important for your health, while others can cause disease (3).

Together, these microbes weigh around 1 to 2 kilos, which is roughly the weight of your brain. Together they act as a kind of extra organ in your body and play a very important role in your health.

How does the intestinal flora affect your body?

Humans evolved millions of years ago to live with microbes. During this time, microbes have evolved to play important roles in the human body. So much so that you may find it difficult to survive without your gut flora.

The intestinal flora begins to influence the body from the moment of birth. Humans first come into contact with microbes when they pass through their mother's birth canal. However, recent research suggests that babies may already come into contact with some microbes in the womb (4, 5, 6).

As the baby grows, the gut flora begins to develop, with the number of different species of microbes increasing. A greater diversity of different microbial species is considered good for health (7).

Interestingly, the food you eat also influences the diversity of your gut bacteria.

As the gut flora grows, it begins to affect the body in a number of different ways. These include:

The digestion of breast milk: some of the bacteria that are the first to grow in babies' guts are called bifidobacteria. They digest sugars from breast milk, which is important for growth (8, 9, 10).
Digestion of dietary fiber: Certain bacteria digest fiber, producing short-chain fatty acids, which are important for gut health. Fiber may help prevent weight gain, diabetes and heart disease and reduce the risk of cancer (11, 12, 13, 14, 15, 16, 17).
Supporting immune system control: Gut flora controls how your immune system works. By communicating with immune cells, gut microbes can control how your body responds to infections (18, 19).
Supporting brain health: New research suggests that gut flora may also influence the central nervous system, which controls brain function (20).

So there are a number of different ways in which gut flora can influence key functions of the body and your health.

Gut flora could affect your weight

There are thousands of different types of bacteria in your gut, most of which are beneficial to your health. However, if you have too many unhealthy bacteria in your gut, this can lead to disease.

An imbalance of healthy and unhealthy microbes is sometimes referred to as dysbiosis and could contribute to weight gain (21).

Several studies have shown that the gut flora was completely different in identical twins, one of whom was obese and the other healthy. This shows that differences in gut flora are not genetically determined (22, 23).

Interestingly, in a study in which the intestinal flora of the obese twin was transferred to mice, it was observed that these mice gained more weight than the mice that had received the intestinal flora of the lean twin, even though both groups of mice followed the same diet (22).

These studies indicate that gut flora dysbiosis may play a role in weight gain.

Fortunately, probiotics are good for gut flora health and can help with weight loss. However, scientific research suggests that the effects of probiotics on weight loss are likely to be quite small, with subjects losing less than 1 kilo (24).

Summary: Dysbiosis of the gut flora could lead to weight gain, but probiotics can potentially restore gut health and help keep weight off.

Gut flora influences the health of the digestive tract

Gut flora can also influence gut health and may play a role in gut disorders such as irritable bowel syndrome and inflammatory bowel disease (25, 26, 27).

The bloated feeling, cramps and abdominal pain experienced by people suffering from irritable bowel syndrome could be due to dysbiosis of the gut flora. This is because microbes produce a lot of gas and other chemicals that can contribute to unwanted symptoms in the gut (28).

However, certain bacteria in the gut flora can also improve gut health. Certain bifidobacteria and lactobacilli, which are found in probiotics and yogurt, can help close gaps between intestinal cells and prevent the development of a pathologically permeable intestinal wall.

These species can also prevent pathogenic bacteria from colonizing the intestinal wall (29, 30). In fact, certain probiotics containing bifidobacteria and lactobacilli can reduce symptoms of irritable bowel syndrome (31).

Summary: Healthy gut flora controls gut health by communicating with intestinal cells, digesting certain foods and preventing pathogenic bacteria from colonizing the intestinal wall.

Gut flora could have an impact on heart health

Interestingly, gut flora could even influence heart health (32). A recent study of 1,500 people found that gut flora played an important role in promoting healthy levels of "good" HDL cholesterol and triglycerides in the blood (33).

Of course, unhealthy species in the gut flora could also contribute to heart disease as they produce trimethylamine N-oxide (TMAO). This is a chemical that contributes to clogging of the arteries, which can lead to heart attacks and strokes.

Certain bacteria in the gut flora convert choline and L-carnitine, which are found in red meat and other food sources, into TMAO, potentially increasing the risk of heart disease (34, 35, 36).

Other gut flora bacteria - particularly lactobacilli - may help lower cholesterol levels when taken as probiotics (37).

Summary: Certain bacteria in the gut flora can produce chemicals that can block arteries and lead to heart disease. On the other hand, probiotics may help lower cholesterol levels and the risk of heart disease.

Gut flora could help control blood sugar levels and reduce the risk of diabetes

Gut flora could also help control blood sugar levels, which could affect the risk of type 1 and type 2 diabetes.

A recent study looked at 33 infants who were at genetically high risk of developing type 1 diabetes. This study found that the diversity of gut flora suddenly decreased before the onset of type 1 diabetes. It also found that levels of a number of unhealthy bacterial species increased immediately before the onset of type 1 diabetes (38).

Another study found that when different people ate exactly the same foods, their blood sugar levels could vary greatly. This could be related to the different types of bacteria in the gut of these people (39).

Summary: Gut flora plays a role in controlling blood glucose levels and could also influence the onset of type 1 diabetes in children.

Gut flora could influence brain health

Gut flora could have a positive effect on brain health in a number of ways. First of all, certain species can help produce neurotransmitters in the brain. Serotonin, for example, is a neurotransmitter with antidepressant effects that is mainly produced in the gut (40, 41).

Secondly, the gut is physically connected to the brain via millions of nerves. Thus, gut flora may also influence brain health by helping to control the messages sent to the brain via these nerves (42, 43).

A number of studies have shown that people with different psychological disorders have different species of bacteria in their gut compared to healthy people. This suggests that gut flora may influence brain health (44, 45).

However, it is unclear whether this is simply due to different dietary and lifestyle habits.

A small number of studies have also shown that certain probiotics can alleviate symptoms of depression and other mental disorders (46, 47).

Summary: Gut flora may influence brain health through the production of brain chemicals and communication with nerves connected to the brain.

How can you improve your gut flora?

There are many ways to improve your gut flora. Here is a small selection:

Eat a wide variety of different foods: this can lead to a wider range of gut flora bacteria, which is an indicator of good gut health. In particular, legumes, beans and fruit contain high amounts of fiber and can promote the growth of healthy bifidobacteria (48, 49, 50, 51).
Eat fermented foods: Fermented foods such as yogurt, sauerkraut and kefir contain healthy bacteria - mainly lactobacilli - and can reduce the amount of pathogenic species in the gut (52). Sauerkraut should not be cooked as heat kills the healthy bacteria.
Limit your consumption of artificial sweeteners: There is evidence that artificial sweeteners such as aspartame may increase blood sugar by stimulating the growth of unhealthy bacteria such as Enterobacteriaceae in the gut (53).
Eat prebiotic foods: Prebiotics are a type of dietary fiber that stimulate the growth of healthy bacteria. Foods rich in prebiotics include artichokes, bananas, asparagus, oats and apples (54).
Breastfeeding for at least 6 months: Breastfeeding is very important for the development of intestinal flora. Children who have been breastfed for at least six months have more beneficial bifidobacteria in their gut than bottle-fed children (55).
Eat whole grain products: Whole grains are high in fiber and beneficial carbohydrates like beta-glucans, which are digested by gut bacteria and may have positive effects on weight, cancer risk, diabetes and other conditions (56, 57).
Try a plant-based diet: Vegetarian diets may help lower levels of disease-causing bacteria such as E. coli, as well as reduce inflammation and lower cholesterol levels (58, 59).
Eat foods rich in polyphenols: Polyphenols are plant compounds found in red wine, green tea, dark chocolate, olive oil and whole grains. Polyphenols are broken down by gut bacteria to promote the growth of healthy bacteria (60, 61).
Take probiotic supplements: Probiotics are live bacteria that can help restore a healthy state of gut flora after dysbiosis. They do this by supplying good gut bacteria that multiply in the gut (62).
Only take antibiotics when they are necessary: Antibiotics kill many bad and good bacteria in the gut, which can potentially contribute to weight gain and antibiotic resistance. Therefore, you should only use antibiotics when really necessary (63).

Conclusion

Your gut flora is made up of billions of bacteria, fungi and other microbes. Gut flora plays a very important role in your health by helping to control digestion and has positive effects on the immune system and many other aspects of health.

An imbalance of unhealthy and healthy microbes in the digestive tract could contribute to weight gain, high blood sugar levels, high cholesterol levels and other disorders.

To support healthy gut flora, you should eat a wide variety of fruits, vegetables, whole grains and fermented foods.

References:

https://www.healthline.com/nutrition/gut-microbiome-and-health

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