vi: The Chemistry Column
Endorphins or ‘outdoorphins’? Claire Gormley Urban living has its perks— most things that you need are just a few steps from your door —but the stress levels of those living in urban environments have also been found to be significantly higher than those living in nature (Lowry et al, 2016). Exercise and going outside are two of the most common suggestions made to people who are looking to de-stress and relax. Not only does exercise physically remove one from a situation that may be causing stress, but it is widely known that exercise releases endorphins which make us feel better. Getting these endorphins pumping isn’t always easy, however, and recent studies into the stress levels of urban versus rural inhabitants point to spending time in nature rather than in the gym. Endorphins are the body’s natural painkillers. Also referred to as endogenous opioids due to the sedative effect they have in common with opiates found in nature, these chemicals leave us feeling relaxed and optimistic after a significant sweat (Grossman and Sutton, 1985; Basso and Suzuki, 2017). They work in two different ways. Some endorphins bind to opioid receptors in the peripheral nervous system and prevent the release of substance P, which is a neuropeptide (a chemical messenger like a neurotransmitter) responsible for sensing pain (Chaudhry and Gossman, 2021). Others can also bind to 26
receptors in the central nervous system and suppress the release of the neurotransmitter gamma aminobutyric acid (GABA). The suppression of GABA consequently increases the production of dopamine, the pleasureinducing neurotransmitter, leading to an increase in mood (Chaudhry and Gossman, 2021). This pathway makes sense to me: the receptors on our neurons help us to experience the world around us, including pain, and accepting that the absence of pain is pleasure is not a far jump to make. What I find more surprising is how going outside produces the same effects. There is some evidence that interaction with plants reduces our psychological stress through the suppression of our sympathetic nervous system (a part of a nervous system that autonomously coordinates our involuntary actions, like breathing and heart rate); however, a different study suggests that it may be the microbes in our gut that actually soothe our stress (Lee et al, 2015; Foxx et al, 2020). According to Foxx et al (2020), Mycobacterium vaccae, along with other soilbased bacteria that have anti-inflammatory and immunoregulatory properties, may be effective stress relievers. These ‘outdoorphins’
