A newly published study in The Journal of Immunology suggests that consuming a high-salt diet may contribute to depression-like symptoms—at least in mice. Researchers found that mice fed a diet high in salt exhibited behaviours associated with depression, and further investigation revealed that this effect was linked to increased production of a specific immune system molecule, IL-17A.
While the study provides intriguing insights, experts caution that more research is needed to determine if these findings apply to humans.
High-Salt Diet Triggers Depression-Like Behaviour
Researchers investigating the effects of salt on mental health found a troubling connection between high sodium intake and depression-like behaviours in mice. One group of mice was fed a high-salt diet, while another group received a standard diet for five to eight weeks.
The results were compelling: the high-salt mice exhibited behaviours similar to those of animals subjected to chronic restraint stress, a model commonly used to study depression.
“These findings suggest that excessive salt consumption may play a role in triggering mood disorders.” On the biological front, the study revealed increased IL-17A production in both the spleens and brains of the high-salt mice, linking the cytokine—known for its association with inflammation and depressive symptoms—to the observed behavioural changes.
The Role of IL-17A and γδT Cells
Researchers wanted to know if IL-17A was directly linked to the depression-like behaviour seen in high-salt diet mice. They used mice genetically modified to lack RORγt, a key factor in IL-17A production, to test this. These mice, despite being fed the same high-salt diet, did not develop the depression-like symptoms.
This strongly indicated that IL-17A is crucial in mediating the effects of dietary salt on mental health.
Further investigation revealed that γδT cells were the primary source of the increased IL-17A levels. When researchers used an antibody to reduce γδT cells, the symptoms of depression-like behaviour in the high-salt mice improved dramatically. The study authors concluded that their findings “suggest that a high-salt diet drives depression-like behaviour in mice through inducing IL-17A production.”
Could High-Salt Diets Affect Mental Health in Humans?
The recent findings on salt intake and mood disorders may offer intriguing insights, but experts are quick to note the limitations of animal research. “Caution is needed when interpreting results from animal studies,” they warn, reminding the public that these results may not directly translate to human behaviour.
Dr. Robert Hostoffer, an American Osteopathic Association board member who was not involved in the study, warned that “in general, it is difficult to interpret data from mouse studies due to their difference in nomenclature of their immune systems, both soluble and nonsoluble components.” He also pointed out that “the determination of depression in mice is difficult to translate to depression in humans.”
However, some experts believe the study opens new doors for future research. Dr. Richard C. Calderone, an osteopathic physician specialising in internal medicine, noted that “although these findings were in mice, it is reasonable to investigate the effect of limiting salt intake on depression in humans.” He added that the study identified “new treatments targeting IL-17A or gamma-delta T cells that may also be targets for pharmacologic management of depression.”
Another Reason to Cut Back on Salt
While researchers continue to explore the possible link between salt intake and depression in humans, health experts are unanimous in their advice to limit sodium. “Excessive salt consumption is already linked to serious health risks, including high blood pressure, stroke, and kidney disease.”
Registered dietitian Karen Z. Berg explained, “High sodium intake is especially bad for your heart and kidneys. People who have heart disease, kidney disease, diabetes, or fatty liver need to really watch their sodium intake so that they don’t make their conditions worse.”
Berg also emphasised the importance of understanding daily sodium limits. “The Dietary Guidelines for Americans recommend that healthy adults limit their sodium to 2,300 mg milligrams per day. That may sound like a lot, but it’s the equivalent of about 1 teaspoon of salt! It is important to look at all labels to see how much sodium you’re consuming.”
Conclusion
The study provides a strong starting point for future research on salt and mental health. The next step will be to determine whether the effects observed in mice extend to humans. Health professionals continue to emphasise a balanced diet with limited salt intake. “This recommendation is rooted not only in physical health benefits but, potentially, in mental well-being as well.”