Depression: Your Brain Is Suffering In Silence Because Of Salt

Researchers have discovered that consuming too much salt, such as that found in fast food, can contribute to the onset of symptoms similar to depression. In tests on mice, a diet high in salt increased the production of an inflammatory substance in the body (IL-17A), which is linked to poor brain function. This suggests that excess salt can affect not only the heart, but also mental health.

Depression is a serious and very common mental disorder that can profoundly affect people's lives. It is estimated that between 15% and 18% of the population will have at least one episode of depression throughout their lives.

This condition not only causes great emotional distress, but is also among the leading causes of suicide and is one of the top ten causes of death in the United States. In addition, people with depression are more likely to develop other diseases, such as infections, autoimmune diseases and even cancer.

On the other hand, when depression is treated, the results of other diseases also improve, for example, patients with advanced breast cancer or people with serious infections respond better to treatment when depression is controlled. Therefore, depression is considered a public health problem of great importance, as it impacts not only the mind, but also the body and quality of life as a whole.

One of the environmental factors that has caught scientists' attention is excessive salt consumption. The Western diet, which includes many ultra-processed foods and fast food, is especially rich in salt (sodium chloride).

To give you an idea, the amount of salt in fast food meals can be more than 100 times greater than in home-cooked meals. This excessive salt intake has been linked to several health problems, such as high blood pressure, heart disease, immune system problems and brain diseases.

Studies have already observed that diets high in salt also appear to be associated with the development of depressive symptoms, but until now it was not known exactly how this happened.

In this study, scientists investigated the effects of a high-salt diet on mice. They found that animals that consumed a lot of salt began to exhibit behaviors similar to those of depression in humans, such as discouragement and lack of motivation.

These effects were accompanied by an increase in the production of an inflammatory substance called IL-17A, which is released by certain cells in the immune system. To better understand this process, the researchers analyzed mice that lacked a genetic factor (called RORγt) necessary for the production of the substance IL-17A.

These mice, despite consuming a lot of salt, did not develop depressive behaviors, which suggests that this substance plays a key role in the link between salt and depression.

In addition, scientists identified a specific type of immune cell, called γδT17 cells, as one of the main cells responsible for the production of IL-17A in these cases.

When these cells were eliminated with the help of a specific antibody, mice that were depressed due to the high-salt diet improved significantly.

Representative images of the immunofluorescence assay of IL-17 expression (in red) in the hippocampus and prefrontal cortex of mice treated with high-dose sodium (HSD) and no-sodium (ND).

These findings are important because they show a possible pathway by which excess salt can influence mood and cause depression, by activating immune cells that generate inflammation in the body and possibly also in the brain.

This suggests that what we eat can affect much more than just our physical bodies: it can directly influence how we feel emotionally.

In summary, the study shows that excessive salt consumption can facilitate the onset of depression, at least in part, by activating inflammatory mechanisms in the body. Understanding this connection may help in the development of new ways to prevent and treat depression, including through simple changes in diet.

READ MORE:

High-salt diet drives depression-like behavior in mice by inducing IL-17A production

Di Lu, Wenjie Chen, Wenhui Sun, Chuan Wei, Xuan Xie, Na Li, Haiyan Yan, Ying Chen, Yue Wu, Zhigang Lei, Lei Xu, Jifeng Zhu, Yalin Li, Chuan Su, Wei Li, Sha Zhou, and Xiaojun Chen

The Journal of Immunology, Volume 214, Issue 4, April 2025, Pages 624–635

doi.org/10.1093/jimmun/vkaf019

Abstract:

Major depression disorder is a common illness that severely limits psychosocial functioning, affects outcomes of other diseases, and diminishes the quality of life. High-salt diet (HSD) has long been closely associated with the occurrence and development of depression, but whether or how HSD causes depression remains unclear. In this study, HSD induces depression-like behavior in mice accompanied by an increase in IL-17A production. RORγt deficiency abolishes HSD-induced depression-like behavior in mice. Furthermore, γδT17 cells are identified as an important cellular source of IL-17A in mice with HSD-induced depression. Depletion of γδT cells using anti-TCRγδ antibody markedly alleviates depression-like behavior in mice with HSD. Our findings demonstrate that increased dietary salt intake facilitates the development of depression at least partially through the induction of γδT17 cells.