Eating too much salt can cause stress levels to increase

In the study, the researchers also took tissue samples from some mice after killing them and found increased activity of genes that produce the proteins in the brain that are responsible for the stress response. “It is interesting to note that these effects are present after a short two-week exposure to a high-salt diet,” says Giuseppe Faraco, assistant professor of neuroscience at Weill Cornell Medicine, who studies the link between salt and cognitive impairment. but was not involved in this study. What Faraco would have liked to see, however, is data on how the overactivation of these key genes relates to the mice’s behavioral response.

Bailey is working on it. Over the next few years, he plans to work with neuroscientists to observe and record how increased salt intake and stress levels manifest in aggression or anxiety-like behavior when mice are placed in specially designed mazes. For example, anxious mice tend to seek safety behind opaque walls and spend more time in closed parts of a maze rather than exploring the open parts where they are more exposed.

Lee Gilman, an assistant professor of behavioral neuroscience, is already conducting these kinds of experiments in their lab at Kent State University in Ohio, investigating how salt intake affects a phenomenon known as contextual fear generalization. This occurs when conditioned fear responses, generated in response to threats that have been experienced, are remembered and extended to safe stimuli. It is considered a hallmark of anxiety-related disorders. “It’s directly related to anxiety processes in the brain,” says Gilman.

Rescued mice will freeze when exposed to the same context in which something threatening took place. But when conditioned mice go beyond this and freeze in a new environment where they’ve never been before, “they generalize the fear,” Gilman says. In their study, which is in preprint, male and female mice were conditioned in a chamber containing a patterned background, an ethanol-based scent, and a light that received mild electric shocks on a stainless steel grid floor.

Four weeks after conditioning, Gilman found that a high-salt diet increased the generalized fear response in women, while the same diet reduced fear expression in men, which surprised the neuroscientist at first. But in previous behavioral studies on salt intake, most researchers had only experimented with male mice, which would explain these gender differences that are only now becoming apparent.

Although these two studies improve our understanding of the effects of a high-salt diet on the brain, Faraco cautions that we must be careful in translating the results to humans. There are differences in how animals and humans absorb, use and metabolize salt, he says. “Comparisons between rodents and humans must be interpreted with caution, given the uncertainty in estimating minimum salt requirements in mice, the relatively short exposure in animal models compared to lifetime exposure in humans, and the known underestimation of human salt consumption.”

Behavioral research is still in its infancy when it comes to salt, but Bailey and Gilman are both working to improve and expand their experiments to track the behavior of mice over longer periods of time. And while their findings can’t be directly extrapolated to humans, they hope people will be a little more aware of their salt consumption, both in general and at times of abundance like Christmas. Currently, most consumers pay attention to the calorie and sugar content when they are served a feast at a communal table – “the salt aspect goes very much under the radar in people’s consciousness,” says Gilman. All of this can change if we discover just what impact it has on our mood and how we feel.

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