Prescription soil. Why does our brain need contact with soil?
When you dip your hands into the moist garden soil, a biochemical cascade is set in motion in your body, the roots of which go back hundreds of thousands of years. This is not a poetic metaphor or a worshipful praise of rural life. This is pure microbial reality. Modern science is increasingly recognizing that the key to our mental balance may be a specific kind of "dirt" from which we try to ward off at all costs in sterile cities.
It all started with cancer patients, although the finale of the story led scientists to a completely unexpected conclusion. In the early 2000s, a research team led by Dr. Mary O'Brien of the Royal Marsden Hospital in London conducted clinical trials on stimulating the immune system in lung cancer patients. The patients were given heat-killed Mycobacterium vaccae, a harmless microorganism commonly found in soil around the world.
Although the therapy did not directly prolong patients' lives, doctors rubbed their eyes in amazement as they analyzed quality-of-life questionnaires. Patients reported rapid, extremely marked improvements in mood. They declared higher levels of happiness, less pain and greater mental clarity. The soil bacterium acted like a potent, natural antidepressant elixir. Scientists urgently needed to answer the question: why?
A shot of happiness from the bed
The answer was provided by neuroscience studies, including those conducted by Dr. Christopher Lowry at the University of Bristol and the University of Colorado. When they exposed mice to Mycobacterium vaccae, they found that this inconspicuous microbe activates exactly the same group of neurons in the brainstem that is responsible for serotonin production.
Serotonin is a key neurotransmitter - it is its retention in the body that most modern psychotropic drugs rely on to work.
Fascinatingly, these bacteria enter the human body extremely naturally when gardening or walking in the woods. All it takes is the inhalation of aerosol floating over raised soil, the accidental introduction of micro-traces into the gastrointestinal tract, or contact through tiny micro-injuries on the hands. From there, through immune pathways and the vagus nerve, the signal goes straight to the structures of the central nervous system.
Worth remembering: Gardening is not a hobby. It's a neurochemical protocol that evolution designed long before we learned to describe it in words.
Cortisol goes down
The microbiological theory is perfectly complemented by behavioral studies. An experiment was conducted in the Netherlands in which a group of people were first subjected to a highly stressful mental task. Then half of the subjects were told to relax by reading a book at home, and the other half were told to work in the garden for thirty minutes. The results of measuring cortisol (stress hormone) levels in saliva were conclusive.
Stress levels dropped in both groups, but the decline was dramatically faster and deeper in the gardeners. Thirty minutes with their hands in the dirt produced a neurochemical effect that reading - while soothing in itself - could not replicate. Physical labor surrounded by nature literally resets our nervous system.
Evolutionary cocktail of happiness
The cycle that gardening funds us is complete and strikes at the absolute foundations of our psyche:
- Serotonin: Released by direct contact with the soil bacterium M. vaccae.
- Dopamine: A reward hormone activated by even modest harvests and satisfaction with the results of one's work.
- Melatonin and Vitamin D: Their production is stabilized by the necessary exposure to natural sunlight.
Old friends hypothesis
From an evolutionary perspective, this mechanism makes profound sense. Our immune and nervous systems were formed in the environment, in constant symbiosis with the microbiota around us. Modern medicine calls this the "old friends hypothesis." By cutting ourselves off from the soil, locking ourselves in sterile concrete offices, we deprive ourselves of the stimuli we were biologically designed to receive.
Today's world requires us to be constantly present in front of computer screens and smartphones. However, our bodies and minds will not be fooled by millions of years of evolution. The hortiterapia (garden therapy) movement is gaining status worldwide as a full-fledged method to help treat anxiety and depression.
So the moral of the latest research is simple, though challenging for the modern man: if you're feeling chronically tired and overstimulated, put down the keyboard for a while. Your mental health simply needs a solid dose of ground today.
Article prepared based on research published in Neuroscience (Dr. C. Lowry) and scientific research on stress reduction (Van Den Berg & Custers).
