The Science Behind The “Sound Body, Sound Mind” Principle

Let us discover the scientific basis of the “sound body, sound mind” principle so prevalently used in sports to forward the idea that physical workout is essential to having healthy psychological well-being.


Mens Sana in Corpore Sanothis Latin phrase which came from Roman poet Juvenal’s Satire X is believed to be the origin of the well-known saying “Sound body, sound mind.” The phrase means “a healthy mind in a healthy body.” Others attribute the saying to the Greeks, particularly to Thales whose existence dated back to the pre-Socratic era.

But what exactly is the moving principle behind the saying? Does it have a scientific backing?

Well, scientists discovered that it does.

Introducing The Kynurenine

2014 saw a group of researchers from the Swedish Karolinska Institutet doing a specific undertaking that explained how a good workout benefited the brain.


According to the team, body muscles produced a particular enzyme that caused kynurenine breakdown when they’re worked out (e.g., workout regimen and the likes). This enzyme breaks and changes the metabolite into an acidic component (the kynurenic acid) and, in turn, makes it unable to cross the barrier that separates the blood from the brain.

Scientific gibberish aside, why is this action necessary? What’s in the kynurenine that makes its uncrossing over to the brain very vital?

The compound is a well-known stress marker. Some past studies have already observed how people with mental disorders such as depression have very high levels of kynurenine. Furthermore, experts believe the metabolite plays an active role in the development of various psychological maladies, Alzheimer’s, even suicide.

However, when kynurenine can’t cross over the blood-to-brain barrier, it is unable to carry on from the changes it does to it at the peak of severely stressful situations, thus, preventing the onset of mental disorders like depression.

Follow Up

Just this year, the same group of researchers from the Karolinska did another follow-up undertaking on kynurenine, this time focusing on its inflammatory properties.

For the recent undertaking, the team fed rats with a high-fat diet causing the animals to become overweight and their blood sugar levels to spike up. Then, they gave them shots of kynurenic acid, the acidic component resulting from the breakdown of the metabolite.

Amazingly, the rats stopped putting on weight even when the proponents didn’t change their caloric intake. Furthermore, their glucose intolerance, which the medical field sees as an indicator for the onset of metabolic disorders, showed significant improvement.


“Our research puts a scientific backing on the saying ‘sound body, sound mind.’ It makes us understand more how advantageous exercising is to the body. It also sheds light on possible novel treatments which we can use to treat metabolic diseases in the future,” said Jorge Ruas, the study’s head researcher.


It’s a ray of hope to a country with a rising number of its population suffering from diabetes and obesity – two conditions that could be curbed or prevented through the workings and the findings of the recently concluded undertaking.

Nevertheless, Ruas admitted their study still has a long way to go.

“The trials are still in the early stages, there’s still a long path ahead, one that we’re determined to tackle,” he concluded.