An excess of salty food seasons the body with stress, study says

Scientists found in studies of mice that a high-salt diet increased the levels of a stress hormone by 75%.

Experts hope the findings will encourage a review of public health policy around salt consumption, with a view to manufacturers reducing the amount of salt in processed food.

The recommended salt intake for adults is less than six grams a day but most people regularly eat about nine grams. This can contribute to higher blood pressure, which increases the risks of heart attacks, strokes and vascular dementia.

While effects on the heart and circulatory system have been well established, little was known about the impact of a high-salt diet on a person’s behaviour.

To study this, experts from the University of Edinburgh used mice, who ordinarily have a low-salt diet, and gave them high-salt food to reflect the typical intake of humans.

They found that not only did resting stress hormone levels increase, but the mice’s hormone response to environmental stress was double that of mice that had a normal diet.

Salt intake increased the activity of genes that produce the proteins in the brain which control how the body responds to stress.

Matthew Bailey, Professor of Renal Physiology at the University of Edinburgh’s Centre for Cardiovascular Science, said: “We are what we eat and understanding how high-salt food changes our mental health is an important step to improving wellbeing. We know that eating too much salt damages our heart, blood vessels and kidneys. This study now tells us that high salt in our food also changes the way our brain handles stress.”

Experts said further studies are already under way to understand if a high-salt intake leads to other behavioural changes such as anxiety and aggression.

The study ties with similar findings suggesting adults who consume more ultra-processed food report more adverse mental symptoms. Researchers in the US showed that individuals who consumed the most ultra-processed foods as compared with those who consumed the least amount had statistically significant increases in the adverse mental health symptoms of mild depression, “mentally unhealthy days” and “anxious days.” They also had significantly lower rates of reporting zero “mentally unhealthy days” and zero “anxious days.” Experts said the findings from this study were generalizable to Western countries with similar ultra-processed food intakes.

“The ultra-processing of food depletes its nutritional value and also increases the number of calories, as ultra-processed foods tend to be high in added sugar, saturated fat and salt, while low in protein, fiber, vitamins, minerals and phytochemicals,” said Eric Hecht, M.D., Ph.D., corresponding author and an affiliate associate professor in FAU’s Schmidt College of Medicine. “More than 70% of packaged foods in the U.S. are classified as ultra-processed food and represent about 60 percent of all calories consumed by Americans. Given the magnitude of exposure to and effects of ultra-processed food consumption, our study has significant clinical and public health implications.”

Experts said data from this study add important and relevant information to a growing body of evidence concerning the adverse effects of ultra-processed consumption on mental health symptoms.