There’s no question that regular exercise is beneficial for the body, but a new study now adds to the growing evidence that working out could have positive health effects for the mind as well. According to the research, which appears in the Journal of Neuroscience, strenuous activity stimulates the production of two key brain chemicals that are known to play a role in regulating mental health issues such as anxiety and depression.
Exactly how exercise affects the brain has had scientists scratching their heads for some time. Several studies have shown that intense physical activity causes metabolic changes in the brain, which increases its anaerobic, or without oxygen, consumption of carbohydrates, meaning its uptake of glucose begins to exceed its uptake of oxygen.
While precisely what happens to the energy obtained from this glucose remains a mystery, several scholars have hypothesized that it could be at least partially used to stimulate the synthesis of the brain's chemical messengers, or neurotransmitters. These molecules diffuse across the gaps between neurons – known as synapses – in order to transmit signals around the central nervous system.
The two most abundant neurotransmitters are glutamate and GABA. Though these are involved in a number of key processes, a deficiency of these compounds has been linked with poor mental functioning and mood disorders.
To test whether exercise causes an increase in levels of these vital neurotransmitters, researchers used a process called magnetic resonance spectroscopy (MRS) to measure their concentrations in the brains of participants following a workout. Results showed that levels of both chemicals were elevated 18 minutes after exercise, returning to normal at about 34 minutes.
Neurotransmitters like glutamate and GABA diffuse across the gaps between neurons in order to carry signals around the central nervous system. nobeastsofierce/Shutterstock
These increases were particularly notable in two brain regions called the primary visual cortex – which processes visual information – and the anterior cingulate cortex. The latter of these forms a key part of the brain’s limbic system, which is responsible for the regulation of emotions, as well as learning and memory. Deficiency of glutamate and GABA in this part of the brain has previously been associated with depression.
In contrast, participants who did not take part in any exercise exhibited no increase in these neurotransmitters, and where level changes did occur, they were always in a downward direction. These results suggest that some of the energy produced in the brain during strenuous activity does indeed contribute to the synthesis of neurotransmitters.
However, since the average increase in glutamate levels following exercise was only 4.9 percent, the study authors suggest that this neurotransmitter boost can only account for a modest 15 percent of the increased carbohydrate uptake in the brain. What happens to the remainder of this energy remains a mystery.
Building on these results, the study authors asked participants to complete a questionnaire in order to obtain information about their daily exercise routines, and found that those who were more active had higher resting levels of glutamate. As such, they conclude that regular physical activity generates lasting increases in glutamate and GABA concentrations throughout the brain, and may therefore have therapeutic potential for those suffering from poor mental health.
It is worth noting, however, that the researchers did not assess participants' mental health during this experiment, and that while these findings are significant, they are by no means conclusive in relation to the role of exercise in treating mood disorders. Indeed, conditions like depression and anxiety are produced by a complex array of factors, and it is likely that neurotransmitter levels regulate symptoms in delicate ways. For instance, while a glutamate deficiency in the limbic system has been linked to depression, an excess of glutamate can cause some neurons to become over-excited, potentially damaging synapses and leading to cognitive impairment or emotional dysregulation.