Hold the fries! Too much salt may be supersizing your stress levels

Over the course of human evolution, our relationship with food has changed dramatically. We’ve transitioned from hunter-gatherer societies, living off the land, to more permanent collectives reliant on manufactured food. Food Evolution (now streaming on Peacock!) traces the controversy around the best way to eat, and feed a continually growing human population, in the modern world. Certainly, all of our innovations in food science have driven a greater quality of life and longer life expectancy, but that doesn’t mean there aren’t improvements to be made.

It's believed that the average person gets about 50% more salt in their diets than they need, a result of so many processed foods many of which are packed with extra salt for flavor. All of that excess salt can lead to an increased risk of heart attack, high blood pressure, strokes, and vascular dementia. While the physical impact of excess salt is relatively well known, the ways in which food impacts our emotional and mental health is less well understood.

Scientists from the University of Edinburgh set out to answer that question in a new paper published in the journal Cardiovascular Research. Pumping people full of extra salt just to see how they behave would be at odds with ethical guidelines — people can eat as much salt as they want as a hobby, but not for science unfortunately — so scientists used mice instead.

The team established an experimental paradigm in which one group of mice were fed on a high salt diet, mirroring the typical intake of the average human, while another group was given an ordinary mouse diet with the regular amount of salt. Over the course of two to eight weeks, scientists measured an increase in resting stress hormone as well as a much higher stress response to environmental stimuli in the high salt test group. In fact, the hormonal response to environmental stressors was roughly twice as high as the control group.

The team observed increased peak levels of plasma corticosterone, Crh, and Pomc mRNA, as well as increased clucocorticoid response. Additionally, the binding properties of some compounds were reduced or downregulated. All which is scientific jargon for a phenomenon in which salt dials up the brain chemicals which make you stressed and turns down the systems meant to mitigate that response. In short, it becomes easier to get stressed, easier to become more stressed than you normally would be, and more difficult for you to reign those feelings in.

Scientists noted several “abnormalities in the glucocorticoid biology,” which increased the activity of genes which produce proteins in the brain for regulating stress response. The stress response is controlled by competing processes, some of which ramp the stress response up while others bring it down. That response is akin to a controlled blaze, burning continuously but trapped inside a ring of stones. Adding salt to our diet is the equivalent of tossing accelerant on the flames. Everything gets hotter, more reactive, and harder to contain.

It stands to reason that if stress levels are increased by higher salt intake, there may be a corresponding increase in anxiety and depression, but researchers stated that more study is needed before they can say for sure. Assuming we have the same relationship with salt as mice do — and that’s not an outrageous assumption, mice are model organisms for scientific research for a reason — those extra-large fries you dig into after a hard day might make you feel better in the moment but they’re supersizing your future stress levels.

Next time someone asks if you want fries with that, it might serve you well to decline. Or at least get them without salt.