Did you know that about 40 billion bacteria live in and on you? Most of these bacteria live in your gut and do not cause health problems. Scientists have even found out that these bacteria are essential for your physical health. New research has shown that these bacteria are also beneficial for your brain and mental health. This article explains how your brain is affected by intestinal bacteria and which role probiotics play in it.
What are probiotics?
Probiotics are living microorganisms, mostly bacteria. They can bring a certain health benefit if enough of it is consumed ( 1). The word probiotic comes from the Latin words ‘pro’, which means promoting (promoting), and the word ‘biotic’, meaning life. To have the term probiotic there must be a lot of scientific evidence to show that a bacterial species is beneficial to health. Unfortunately, the word is used and used by food and pharmaceutical companies that labeled some bacteria as probiotic, even if there was no scientific evidence for this. This has led the European Food Safety Authority (EFSA) to banish the word ‘probiotic’ on all food in the European Union. However, there is a lot of new evidence showing that some types of bacteria actually bring health benefits .2,, 3, 4, 5, 6 ). Most probiotics belong to one of the two types of bacteria: Lactobacilli or Bifidobacteria. There are many different species and strains within these groups and they can have different effects in the body.
In short : Probiotics are living microorganisms that have proven health effects for the body.
How are the intestines and brains connected?
The intestines and brains are physically and biochemically linked. The physical connection between the intestines and the brain exists through the central nervous system, which regulates all body activities. The vagus nerve is a large nerve that sends signals between the intestines and the brain ( 7 ). The brains are also connected to the intestines by intestinal microbes. Molecules produced here can act as signals that the brain can detect ( 7 ). Previously, scientists estimate that a person has about one hundred trillion bacteria cells in the body and only ten million human cells, which means that your own cells have been surpassed by ten to one ( 8). Recent estimates indicate, however, that a human being has about thirty million human cells and forty trillion bacteria. This is still quite impressive and means that you are more bacteria than humans ( 9 ). The majority of the bacteria are in the intestines and are in direct contact with the cells that line your intestines with everything that enters your body. This applies to food, medicine and microbes. In addition to your intestinal bacteria, there are many other microbes, such as yeast and fungi. These microbes are known as the intestinal flora or microbiome ( 10 ). All these bacteria can produce different substances, such as short-chain fatty acids, neurotransmitters, and amino acids. Many of these substances affect the brain ( 11). Apart from the production of substances that influence the brain, intestinal bacteria can also influence the brain and the central nervous system by regulating inflammation and hormone production (12, 13 ).
In short : There are thousands of different types of bacteria in the human body, mainly in the intestines. These bacteria are generally good for your health and can even affect your brain health.
A damaged intestinal flora can contribute to various diseases The term intestinal dysbiosis means that the intestines and intestinal bacteria are in a diseased state. This can be due to the presence of pathogenic bacteria, which can also lead to chronic inflammation. An affected intestinal flora has been found in people with obesity, heart disease, type 2 diabetes and other diseases (14, 15, 16, 17 ). Some studies have shown that certain probiotics can restore the intestinal flora to a healthy state and reduce the symptoms of these diseases (18, 19, 20, 21
). Some studies have shown that people with certain brain disorders also have a damaged intestinal flora. However, it is unclear whether this is the cause of the disease or a result of the diet and lifestyle (22, 23, 24, 25 ). Since the intestines and brains are connected, and the intestinal bacteria produce substances that affect the brain, probiotics can be beneficial to the brain. A number of recent studies have examined this, but mainly in animals. Some of these, however, have yielded interesting results in humans.
In short : A number of diseases, including brain abnormalities, are linked to a higher number of pathogenic intestinal bacteria. Some probiotics could restore the healthy bacteria to reduce the symptoms.
Taking probiotic supplements may reduce the symptoms of stress, anxiety and depression Stress and anxiety are common and depression is one of the leading causes of disease worldwide ( 26 ). A number of these disorders, especially stress and anxiety, have been associated with high cortisol levels, the human stress hormone (27, 28, 29 ). Only one study has investigated how probiotics affect patients with depression. Taking a mix of three Lactobacilli and Bifidobacterial strains for eight weeks significantly reduced symptoms of depression in the study. The probiotics also reduced inflammation in the patients ( 30
). A handful of other studies have investigated how probiotics affect depressive symptoms in healthy people. In healthy people, certain probiotics can reduce the following things:
- Symptoms of anxiety (31, 32, 33 )
- Symptoms of depression ( 34 )
- Psychological disorders ( 35 )
- Academic stress ( 36 )
In short : Certain probiotics can reduce symptoms of anxiety, stress and depression in healthy people. More research is needed into the possible benefits for people with clinically diagnosed psychological disorders.
Taking probiotic supplements may reduce the symptoms of irritable bowel syndrome. The irritable bowel syndrome (PDS) is directly linked to the function of the colon, but the disease is sometimes considered a psychological condition (37, 38 ). Anxiety and depression are common among people with IBS. People with IBS often have an affected intestinal flora (39, 40, 41 ). Many studies have shown that certain probiotics can reduce the symptoms of IBS, such as pain and bloating (42, 43, 44 ).
In short : PDS is often linked to an increased feeling of tension and depression. Probiotics seem to help reduce the symptoms.
Some probiotics can improve mood In healthy people without mental illness, some probiotics can help improve mood. A study treated participants daily for four weeks with a probiotic mixture with eight different Lactobacilli and Bifidobacterial strains. The researchers found that taking the supplements reduced negative thoughts linked to a bleak mood ( 45 ). Another study showed that taking a dairy drink with probiotics called Lactobacillus casei for three weeks improved mood in people with the worst mood before the start of treatment ( 46
). This study also showed that people scored slightly lower in a memory test after taking the probiotics. Further research is required to confirm these results.
In short : A number of studies have shown that taking certain probiotics for a few weeks can improve mood.
Certain probiotics can be beneficial after traumatic brain injury In case of a traumatic brain injury, people usually end up in the intensive care unit. During the stay in intensive care, food is usually administered via a tube. In some cases, the patient is also on the ventilator, which may increase the risk of infection. Infections in people with a traumatic brain injury can lead to complications. A number of studies have found that the addition of certain probiotics in tube feeding can reduce the number of infections in patients with a traumatic brain injury and shorten the stay in the intensive care unit (47, 48, 49).
). The effects of the probiotics on these outcomes can be attributed to the positive influence on the resistance.
In short : administering probiotics after a traumatic brain injury can reduce the risk of infections and shorten the stay in the intensive care unit.
Other positive effects of probiotics on the brain A handful of other studies have shown that probiotics can have positive effects on the brain. An intriguing study looked at brain scans of women after the consumption of a mixture of Bifidobacteria, Streptococcus, Lactobacillus and Lactococcus strains. The consumption of probiotics affected parts of the brain that control emotions and feeling ( 50 ). Other studies have shown that certain probiotics reduce the symptoms of multiple sclerosis and schizophrenia, but more research is required (51, 52 ).
In short : Some probiotics can influence the brain function and symptoms of multiple sclerosis and schizophrenia. However, this research is very recent, so the results are not clear.
Do you have to take probiotics for your brain? Currently, there is insufficient evidence to definitively state that probiotics are beneficial for the brain. Therefore, they can not be considered as a treatment for brain disorders. Consult your doctor if you want to treat such a condition. Having said that, there is clear evidence that probiotics can be beneficial for other health aspects, including heart complaints, digestive disorders, eczema and dermatitis (3, 4, 5, 53
). So far, scientific research shows a clear link between the brain and intestines. It is an exciting research area that is growing at a rapid pace. A healthy intestinal flora can usually be obtained through a healthy diet and lifestyle. Some foods, including yogurt, sauerkraut, kefir, and kimchi, usually contain good bacteria. Probiotics supplements can, if necessary, increase the number of beneficial intestinal bacteria. Taking probiotics is generally safe and involves few side effects. If you buy probiotics, opt for a product with scientific substantiation. Lactobacilli GG (LGG) and VSL # 3 have both been extensively studied and have demonstrated a proven number of health benefits.
In short : Probiotics are beneficial for other health aspects, but there is still insufficient evidence to definitively state that probiotics have positive effects on the brain.
In conclusion, Although the studies are promising, it is too early to recommend probiotics for healthier brains. The current evidence, however, provides sufficient brain food to further reflect on how probiotics can improve brain health in the future (with permission translated) .