03.05.2021 Nutrition

Does happiness start in the gut?

That ‘gut feeling’ is our body telling us something and it pays to listen, says Olivier LeJus

We have probably all experienced both the stomach tension and nausea associated with stress and, in contrast, the wonderful feeling of contentment after a good meal to know there is a close connection between our emotions and our guts. But how much is our digestion affecting our happiness?

According to Gulia Enders, the celebrated German author of the best-selling book Gut, the cooperation between our digestive system and our brain begins at a very early age.

As every mother knows, our digestion is responsible for a very large part of our emotional state when we are little. A well-fed baby is a happy baby, and the emotional attachment we have with food continues into adulthood, which explains why it is so difficult to make long term changes to somebody’s diet.

The gut is the biggest sensory organ in the body.

It possesses not only a very sophisticated network of nerves, but also a huge collecting surface area in comparison to other sensory organs like the eyes, nose, or ears.

The vagus nerve, which runs all the way from the base of the brain to the large intestine, is the longest cranial nerve in the body. It provides the vital link between the guts and the nervous system, constantly sending feedback regarding hormones and immune cell levels from the digestive organs to the brain for regulation.Human experiments have shown that volunteers can be made to feel more relaxed or more anxious depending on the level of stimulation frequencies applied on their vagus nerve.

Surprisingly, it wasn’t until very recently that scientists began seriously investigating the influence of our digestive system on our emotional wellbeing.

Laboratory mice are the guinea pigs of medical research. Unfortunately, they are even worse than men at expressing their emotions, so in order to test the effectiveness of medications on their mental state, scientists have devised a fairly unpleasant test which helps to select mice with depressive tendencies.

All test subjects are placed in a water container, which is too deep for them to reach the bottom with their feet, thus forcing them to swim round and round in a vain attempt to reach firm ground.

Mice suffering from depression, like human beings, have a stronger reaction to stress than others.

When they are placed in challenging situations like forced swimming, they lose the will to fight and quickly give up. This makes them ideal candidates for testing antidepressants. The longer they can swim after being injected with a drug, the more effective the mood altering substance.

In 2011, when a team of Irish scientists fed their laboratory mice a specific strain of bacteria which is beneficial for the guts, they discovered their animal subjects not only kept swimming for much longer, but the levels of stress hormones in their blood were significantly lower. Their mice had also become smarter and were now performing better in memory and learning tests than their peers.

Two years later, the first study involving humans revealed that after the volunteers had ingested a cocktail of bacteria for four weeks, the area of their brain associated with processing emotions and pain had changed.

When the brain is under stress, it puts a lot of effort into trying to process the problems it is facing. As the level of adrenalin rises, extra energy and blood supply is immediately diverted from the digestion to the nervous system to face this emergency situation.

If the stress remains, the digestive system is being gradually starved of energy and starts sending negative signals to the brain expressed as fatigue, loss of appetite, bloating, or diarrhoea.

I have painful memories as a teenager of having to rush to the toilet to vomit after another argument with my father. It is much later that I discovered that when we are overwhelmed by a stressful situation and experience emotional vomiting, the digestive system is getting rid of undigested food to quickly divert much needed energy to the brain. When the situation becomes chronic, the constant lack of supply to the gut causes the thin protective layer of mucus lining the stomach to become thinner and more sensitive to certain foods.

We can see how this can produce Irritable Bowel Syndrome (IBS), which is expressed by bloating, and alternating episodes of diarrhoea and constipation in patients with a tendency towards anxiety and depression. Another theory is that repeated stress changes the gut flora, allowing different bacteria to survive, with the effect lasting long after the stressful episode is over.

The way we make decisions based on our“gut feeling” could be the result of how the stomach responded when placed in a similar situation in the past.

Which brings us back to the importance of enjoying our meals at a leisurely pace in a relaxed setting without outside distraction.

In the environment we live in, being able to leave our smart phone alone during lunch break is no easy task, but it will definitely lead to a happier life, and stomach, in the long run.

Olivier Lejus
