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What Is the Link Between Gut Health and Brain Function? Can Eating Better Improve Your Mental Health?

Our gut and brain communicate with each other all the time. In response to stress or feelings of nervousness, the digestive process may slow down or be temporarily disrupted, causing stomach pain and other symptoms of functional gastrointestinal disorders. Indeed, we all know what it’s like to have “butterflies in our stomach.” But did you know that the reverse is true—that gastrointestinal problems can cause stress and anxiety? To learn how your gut microbiome affects and communicates with your brain, as well as how Mana can help, continue reading our new blog post.

Scientific evidence accumulated over the last decade shows that gut microbiota affect some aspects of brain function and behaviour, including emotional behaviour. They can influence our cognitive functions like memory, and lead to weight gain or obesity. The disruption of the microbiome’s symbiosis can even lead to neurodegenerative disorders, like depression, autism, schizophrenia, or, as recently discovered, Alzheimer’s disease.

Gut microbiota—the forgotten organ

Our gut is home to trillions of microorganisms, like bacteria, archaea, fungi, protists, and viruses. We call these communities our microbiota. There are over 1,000 different species of bacteria living in our gut. They play a critical role in both the maintenance of human health (digestion, regulation of metabolism, regulation of the immune system) and the pathogenesis of disease by preventing colonisation by harmful bacteria and viruses. 

There are 1-2 kg of microbiota living in our gut, so it’s no surprise that they are sometimes referred to as our “forgotten organ.” (For reference, the human brain weighs about 1.5 kg.) The full collection of all our microbiota and any genes that exist in the gut is collectively referred to as our gut microbiome.

Every person has a unique set of microbiota, influenced by their age, sex, whether they were born naturally or via C-section, enviroment, diet, and any medications taken. It can remain unchanged for years or undergo relatively rapid transitions. These little beneficial organisms in our gut produce vitamins and other metabolites with positive health effects. The bidirectional communication between the brain and gut—the gut-brain axis—plays a key role in maintaining brain health.

The gut-brain axis

There are several ways through which the brain and the gut communicate and send signals to each other. The ENS (enteric nervous system, sometimes called our “second brain” because it is lined with almost 100 million nerve cells) and CNS (central nervous system) communicate with each other to form the gut-brain axis. 

Bidirectional communication is mainly realized through the vagus nerve (the most complex nerve) and through the production of signaling molecules such as gamma-aminobutyric acid (GABA), dopamine (our “motivator”), serotonin (nature’s antidepressant) and short chain fatty acids (SCFAs). These signaling molecules can modulate CNS function by reducing inflammation, relieving stress response, and improving mood.

The most important of these molecules is serotonin. It is proven that inability of the body to produce enough serotonin contributes to the development of depression. More than 90% of the serotonin in our body is produced in our gut. Initial studies have determined that gut microbiota can regulate our levels of tryptophan, which is the main precursor to serotonin.

Studies by Frontiers in Behavioral Neuroscience conducted in 2019 on germ-free mice demonstrated that microbiota influence stress reactivity and anxiety-like behavior, as well as memory loss. The animals demonstrated an increased stress response to decreases in microbiota. Microbial colonization of the gut leads to normalization; the presence of microbiota itself also leads to the stimulation of the serotonergic system.

Chronic treatment with probiotics in these germ-free animals reduced the release of cortisol (our stress-hormone), as well as the frequency of anxiety- and depression-related behavior.

The hypothalamic-pituitary-adrenal (HPA) axis represents another pathway of gut–brain crosstalk. It not only controls the body’s reaction to stress (by regulating cortisol levels), it affects digestion, the immune system, mood and emotional status, and energy storage. Dysregulation of HPA activity is associated with mental health disorders such as depression and schizophrenia.

SCFAs, like butyrate or propionate, also help combat the effects of asthma, arthritis, and even autism. The SCFAs acetate, propionate, and butyrate are the main metabolites produced in the colon by bacterial fermentation of dietary fibres and resistant starch.

Last but not least, the gut-brain axis runs through the immune system. The immune cells in the intestine make up the largest part of our immune system. In fact, the lymphoid tissue connected to and associated with the gut makes up about 70% of the body's immune system. Our gut microbes play an important role in inflammation by controlling what is absorbed by the body.


The structure of serotonin, which influences our mood, cognition, memory, and more. Over
 90% of the serotonin in our bodies is produced in our gut.

Are we really what we eat?

So, what does this all mean? Could it be that by changing the types of bacteria in your gut, you can improve your mental health? Yes. If you regulate or modify your microbiome through your diet, you may improve your mental, physical, and emotional health. You may feel more energetic, be sick less often, and have better mental clarity.

It is important to have a diverse diet, because certain microbes need certain organic substrates to live. Eating a diverse range of foods leads to a diverse microbiome and is therefore an indicator of good gut health. 

A recent English-American study by the Predict research project involving more than 1,000 people showed, for the first time, that a balanced diet rich in nutrient-dense foods supports health and diversity of gut microbiota, while eating highly processed foods with added sugar and salt can lead to less diverse and “unhappy” microbiota, as well as poor metabolic health.

In addition, English-American researchers found that eating plant-based foods is much healthier for the microbiome than meat. Also, the diversity of gut microbiota is not so much dependent on our genetics as it is on what we consume.

Organic molecules, obtained by digesting food as well as via microbiota, are built into our bones, muscles, and nerves. So, quite literally, we are what we eat.

Mana: food for guts and brain

Mana as a nutritionally complete food helps to keep your intestines healthy. It is a source of fibre and omega-3 fatty acids, which support optimal communication between the gut microbiome and the brain.

Soluble and insoluble fibres are an integral part of our diet and offer many health benefits. Soluble fibre plays a very important role in the proper function of the gut-brain axis because it acts as an intestinal prebiotic by supporting the growth of friendly gut bacteria, which we refer to as probiotics. It also strengthens the immune system and aids digestion. Insoluble fibre, i.e. that which our bodies cannot absorb, regulates the absorption of fat, cleanses the intestines, and leaves us feeling satiated after eating.

Probiotics are live bacteria. When administered in quantities sufficient to produce benefits in patients suffering from psychiatric illness, they are referred to as psychobiotics. Experts are studying psychobiotics and hope that they may in the future be part of a new group of psychotropic drugs that serve as a less harmful alternative to common antidepressants. Some Lactobacillus and Bifidobacterium strains produce GABA, which causes elevated plasma levels of tryptophan—a precursor for serotonin. Probiotic foods include yogurt, kombucha, kimchi, and sauerkraut.

One serving of ManaPowder delivers 7 g and one serving of ManaDrink 4.4 g of fibre, which supports the growth and function of gut bacteria. Our latest recipe of Mana, Mark 6, contains a balanced amount of soluble and insoluble fibre from a total of 8 sources, including oat fibre with significant beta-glucan content, pea fibre, carrot fibre, and chicory fibre (also known as inulin).

Omega-3-fatty acids can also increase the amount of good bacteria in the gut and improve brain function. One serving of ManaPowder delivers 1.4 g of omega-3-fatty acids, while one ManaDrink delivers 1.1 g (incl. EPA and DHA, which contribute to the maintenance of proper heart and brain function).

High-protein foods like chicken and eggs are rich in tryptophan—the amino-acid that, as aforementioned, is converted into the neurotransmitter serotonin. Although Mana is 100% plant-based, it will supply you with complete protein with a balanced spectrum of all 9 essential amino acids, including tryptophan.

So, in conclusion, our gut and our brain are in continuous communication. The high variety of sources of fibre and omega-3s in Mana helps to keep our gut healthy and supports optimal communication between the microbiome and the brain. To keep our microbiota happy, it is essential to eat a varied diet.

On top of that, we should also try to sleep well, reduce emotional and physical stress, and take antibiotics only when medically necessary (since they kill both the good and bad bacteria in your gut). The next time you feel anxious, nervous or sad, listen to your gut and think of the millions of microorganisms that, if you take good care of your microbiome, will thank you by improving your brain health and
mood.


Sources:

[1] K. Schmidt, P. J. Cowen, C. J. Harmer, G. Tzortzis, S. Errington, P. W. J. Burnet (2014) Prebiotic intake reduces the waking cortisol response and alters emotional bias in healthy volunteers.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4410136/

[2] M Hasan Mohajeri, Giorgio La Fata, Robert E Steinert, Peter Weber (2018) Relationship between the gut microbiome and brain function.
https://academic.oup.com/nutritionreviews/article/76/7/481/4985887

[3] Iva Lukić, Dmitriy Getselter, Omry Koren, Evan Elliott (2019) Role of Tryptophan in Microbiota-Induced Depressive-Like Behavior.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6558209/

[4] M. Carabotti, A. Scirocco, M. A. Maselli, and C. Severi (2015) The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4367209/

[5] Harvard Health Publishing (2021) The gut-brain connection.
https://www.health.harvard.edu/diseases-and-conditions/the-gut-brain-connection

[6] Nature & The Integrative HMP (iHMP) Research Network Consortium (2019) The Integrative Human Microbiome Project.
https://www.nature.com/articles/s41586-019-1238-8

[7] F. Asnicar, S. E. Berry, N. Segata (2021) Microbiome connections with host metabolism and habitual diet from 1,098 deeply phenotyped individuals.
https://www.nature.com/articles/s41591-020-01183-8 

[8] Pascale A, Marchesi N, Marelli C, Coppola A, Luzi L, Govoni S, et al. Microbiota and metabolic diseases. Endocrine. (2018) 61:357–71. doi: 10.1007/s12020-018-1605-5

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