“Butterflies in the stomach”, “Gut instinct”, “Nervous stomach”;
There are many expressions linking emotions to our digestive tract. In fact, the gut is often referred to as the “second brain.” Rather than being a figure of speech, this is a physiologically accurate portrayal. The gut is innervated by the two branches of the autonomic nervous system, which is controlled by the brain, as well as by the enteric (of the intestines) nervous system, which operates entirely independently. Serotonin, the neurotransmitter famous for its role in treating depression and insomnia, is highly active within the gut and ninety five percent of the body’s serotonin is actually manufactured in the intestines. No wonder people with gut dysbiosis, or an altered balance of bacteria and yeast in the gut, experience mood symptoms! Perhaps it would be more precise to label the gut as part of the brain? In any case, it is clear that the health of our gut affects our mood, and our mood affects the health of our gut.
So, what happens in our nervous system when we are stressed out??
When we are in a “stressed out” state, the sympathetic branch of the autonomic nervous system is dominant. And while that sounds friendly enough, this is the branch that evolved to help us escape a perceived physical threat. The sympathetic nervous system governs “fight or flight” reactions. So we have blood flow to our muscles and away from our gut, increased heart rate, dilated pupils. All great things if you need to run away from a large animal, but not much use today, as most of our perceived stressors are psychological, not physical. And as people often experience every day of their lives as stressful, the biochemistry of the stress response is maintained over the long term.
Fundamentally, we cannot digest well – either food or ideas – in a sympathetic state. The biochemical and physiological changes involved in what is known as the “Stress Response” have been well-studied. One important piece is that stress stimulates increased production of cortisol from the adrenal glands. Cortisol not only decreases inflammation in the body (this is why corticosteroid drugs are used), but overall alters immune system function, causing a cascade of potential consequences from decreased sex hormone production to decreased thyroid hormone activity. Altered immunity in the gut can lead to inflammation, which can then lead to further problems ranging from pain to decreased nutrient absorption to food sensitivities.
Some possible consequences of sympathetic dominance include peptic ulcers, indigestion, constipation and diarrhea, muscle aches, insomnia, and mood instability. Other conditions biochemically linked to long-term stress include diabetes, hypertension, abdominal weight gain, and decreased libido. Oi!
In contrast, the parasympathetic nervous system allows us to “rest & digest,” sending more blood to the digestive tract, increasing gut motility and secretions, slowing our heart rate, and enhancing our ability to absorb nutrients and store food as fuel. There is ample evidence that cultivating a “Relaxation Response” enhances well-being. By decreasing sympathetic nervous system activity, we not only feel relaxed in the moment, but can sustain a decreased responsiveness to stress. And less biochemical stress is central to the prevention and management of a range of health concerns.
Thus taking time for yourself, whether it is 5 minutes of deep breathing at your desk, a day of hiking with a friend, or enjoying a cup of herbal tea, is not wasting time, or being selfish. It is central to maintaining and attaining optimal health!