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A connection that is good to know

You may be familiar with expressions such as: “butterflies in my stomach”, “pit in my stomach”, “that makes me want to throw up” or “I’ve got a gut feeling…”. If we are in love, we have ‘butterflies in our stomach’, if we are scared, we have ‘a knot in our stomach’. We ‘swallow our disappointments’ and ‘digest defeats’. Why is it that certain feelings cause a physical reaction with digestion, whether pain or pleasure? The answer would be that “feelings that come from our digestive system” suggest that our brain and intestines are connected.

Sensitive intestines

Our bodies have over 40 trillion bacteria, and most of them can be found in our intestines (about 700 different types of bacteria live in our intestines alone). This community of bacteria and microorganisms in the gut is called intestinal microbiota. Bacteria from the gut play an important role. In addition to helping break down food, they produce and regulate key neurotransmitters and hormones (for example, the gut produces 90% of the “happiness hormone” serotonin, along with other important mood-related neurotransmitters).

The peristaltic reflex or “law of the intestine” tells us that the intestines use wave-like motions of the muscles to push food content always in the same direction, from oral to anal. Scientists have proven that this phenomenon does not require a connection to the central nervous system, which means that the nerves inside the gut are responsible for this.

The intestinal nervous system is a complex system made up of about 100 million nerves, which are located in the intestinal mucosa. The intestines not only have an inconceivable number of nerves, but also a countless variety of these nerves. There is only one other organ that has such a range of nerves, and that is the brain. The neural network of the intestine has structural and chemical similarities with the brain, which is why the intestines are also called the “second brain”.

Direct communication

What happens in our gut is sometimes a matter of life and death. The brain needs to know if our intestines are empty or if there is a problem that interferes with the breakdown of food. Also, if our intestines are facing an attack of pathogens, our brain needs to react.

Intestinal and brain “conversations” have long been of interest to scientists. However, a new level to this “partnership” has recently emerged. Scientists have been studying the influence of our microbiome on the connection between the gut and the brain, i.e. does the bacteria in our gut affect our psychology and behavior? The first traces of such research began more than 20 years ago. Subsequent studies have confirmed the influence of the microbiome on states of mind and also established the influence on anxiety and depressive behavior. Another key observation has linked dysbiosis (microbial imbalance) to autism. Children with autism often have irregular and less diverse communities of bacteria in their gut.

Stress is known to increase the permeability of the intestinal mucosa which allows bacteria easier access to both the immune system and the neural cells of the intestinal nervous system. This is one of the ways bacteria finds a way to affect us. However, there is a more direct path via the vagus nerve. A study used food-borne pathogens to provide evidence that bacteria in the gut can activate stress circuits by directly activating the vagus nerve.

One of the longest nerves in the body, the vagus nerve establishes a physical connection directly from the gut to the brain, transmits messages, and maintains constant communication between them. The vagus transmits information in both directions, but most of the data is sent by the gut (up to about 90% of transmitted messages travel from the gut to the brain) which means that whatever happens in the gut is reflected on the brain as well. But what affects the quality of that communication? Studies have shown that sensory neurons in the gut are less active in mice deprived of good bacteria, and once these mice are given probiotics to restore the microbiome, the level of neuronal activity returns to normal.

Although this area is still being explored, scientists have concluded that it is possible to manipulate the intestinal microbiota to positively affect neuronal functions.

How to maintain a good connection?

Since the bacteria in our gut affect brain health, changing our gut bacteria can also improve our mental health.

Our body is full of good bacteria and probiotics (live bacteria and yeast) that help maintain the health of our intestines. Probiotics are also called functional foods, meaning that they have an active biological effect, which helps maintain one’s health and affects certain bodily functions. But not all probiotics are the same. Probiotics that affect the brain are often referred to as “psychobiotics”. Some probiotics have been shown to significantly reduce the symptoms of stress, anxiety and depression.

How can we influence or maintain a good connection between our brain and gut? The answer is, as in most cases, by eating and choosing foods that can maintain a strong balance in favor of good bacteria in the digestive tract:

  • Omega-3 fatty acids: research shows that omega-3 fatty acids can increase good bacteria in the intestines and reduce the risk of brain disorders.
  • Fermented food: homemade kefir, yogurt, sauerkraut and cheese contain good bacteria.
  • Food rich in fiber: whole grains, nuts, seeds, fruits and vegetables contain prebiotic fibers that are beneficial for your good bacteria.
  • Food rich in polyphenol: cocoa, green tea, olive oil and coffee contain polyphenols, plant chemicals that digest your intestinal bacteria.
  • Food rich in tryptophan: Tryptophan is an essential amino acid used in the synthesis of the neurotransmitter serotonin in the body. Food high in tryptophan includes meat (especially beef, lamb, turkey and chicken), fish (mostly salmon, cod, sardines, tuna), as well as milk and eggs. Many plant foods are also rich in tryptophan – eggplants, potatoes, lentils, soybeans, beans, spinach, kale, buckwheat, chickpeas, lettuce, apricots, bananas, rye, oats, sunflower and pumpkin seeds, as well as green beans, zucchini, cauliflower, celery, peas, tomatoes, mushrooms, beets, onions, and garlic.

To support good bacteria and their work, here are two simple and delicious recipes:

Banana puree with milk kefir

Creamy smoothie with water kefir

Banana puree with milk kefir

  • 1 banana
  • 250 ml homemade milk kefir
  • 2 tbsp coconut flakes
  • 3 strawberries

To get a thicker consistency (such as with oatmeal), mash the banana “coarsely”. Add kefir and coconut flakes and blend.

Add sliced strawberries and enjoy!

Creamy smoothie with water kefir

  • 300 ml water kefir
  • 1 slice fresh pineapple 1 cm thick
  • 1 small apple (I used Golden Delicious)
  • 2 dates

Blend all ingredients for about 10 seconds and enjoy the flavors.


Book: “Gut: The Inside Story of Our Body’s Most Underrated Organ” by Giulia Enders

The Gut-Brain Connection: How it Works and The Role of Nutrition

The Gut Brain Connection: How Gut Health Affects Mental Health

The gut-brain connection

Probiotici, prebiotici, simbiotici, psihobiotici i upalne bolesti crijeva

On communication between gut microbes and the brain

Gut-Brain Connection

Gut bacteria and the brain: Are we controlled by microbes?