- The link between diet and depression is a critical area of research. It could lead to finding effective strategies to treat depression.
- A study found that mice who consumed a high-salt diet developed depression. The findings also suggested that this was because the high salt diets affected the production of the cytokine IL-17A.
- The results highlight another potential reason to limit salt consumption.
The World Health Organization (WHO) estimates that
Experts want to find effective treatment strategies, and one area of focus is diet, with evidence suggesting that following a healthy diet and avoiding components like junk food may help decrease depression risk.
A study recently published in The Journal of Immunology looked at the relationship between consuming a high-salt diet and depression-like symptoms in mice.
They found that mice who received a high salt diet developed depression-like symptoms and that this was likely related to the induced production of the cytokine IL-17A.
The results open the door for future research into depression and possible treatment.
Researchers sought to explore how high salt consumption affected depression in mice. First, they tested if mice who received high salt diets developed depression.
Mice had either a normal or a high-salt diet for 5 to 8 weeks. Researchers used a few methods to look at mice’s behavior. They also had a positive control group of mice that were exposed to chronic restraint, which is “a common depression-like model.”
The mice on the high-salt diet displayed behaviors similar to those of the positive control mice. This indicates that the high salt-diet caused the mice to exhibit depression-like behavior.
They also found that these mice experienced an increase in the production of
Their analyses revealed that certain cells produced more IL-17A, and they also found increased levels of IL-17A in mice’s spleens and areas of the brain. This suggests that the high salt diets promoted the production of this critical cytokine.
To further investigate this, researchers used mice with a RORγt deficiency. They note that this transcriptional factor is something that is needed for IL-17A to be produced.
They fed these mice the high-salt diet and then saw if they developed depressive symptoms. These mice demonstrated much more normal behavior than those with the transcriptional factor. These mice also did not experience increased levels of IL-17A.
The authors note that their findings “suggest that [a high-salt diet] drives depression-like behavior in mice through inducing IL-17A production.”
The researchers note that several lymphocyte populations can produce IL-17A, so they next tried to determine the distribution of cells that make IL-17A in the mice’s brains, peripheral blood, and spleens.
They found that γδT cells were likely a major cell source of the increased levels of IL-17A in the mice that received the high-salt diets.
The results also indicated that mice on the high salt diets experienced an increase in γδT17 cells. Researchers note further that the γδT17 cells were a critical source of IL-17A in the mice who received the high-salt diet.
Finally, researchers wanted to see if the production of IL-17A by the γδT cells contributed to the depression behavior of the mice who received the high-salt diet. To do this, they used an anti-γδTCR antibody to diminish the γδT cells. They found that after this, the depression-like behavior in high-salt diet mice diminished.
The authors note that “[c]ollectively, our findings show that [a high-salt diet] drives depression-like behavior in mice at least partially through the induction of γδT17 cells.”
The results uncover critical information about how salt intake could impact depression.
Richard C. Calderone, DO, MPH, FAAP, FACP, an osteopathic physician specializing in internal medicine, who was not involved in this study, noted to Medical News Today that:
“Although these findings were in mice, it is reasonable to investigate the effect of limiting salt intake on depression in humans. It should be noted that depression is a complex, multi-factorial condition, and that even with promising studies like this —it remains too early to know the quantity of salt intake necessary to demonstrate any clinical difference in humans. In addition to dietary salt restriction, this study identified that new treatments targeting IL-17A or gamma-delta T cells may also be targets for pharmacologic management of depression. The study provides a biological explanation for the association between high salt intake and depression, identifying new targets for potential treatments.”
This research used mice, often a critical data collection component that provides useful information. However, more research will likely be needed to confirm what this study found.
Robert Hostoffer, DO, an American Osteopathic Association board member, not involved in the study, told MNT 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.”
“Caution should be employed with the data in reference to human subjects. Also, the determination of depression in mice is difficult to translate to depression in humans,” Hostoffer advised.
More research would be required to see if people would experience similar results and what the long-term effects might be. Additionally, more research to confirm the findings on the γδT cells may also be helpful.
The study authors noted that examination of the molecular mechanisms involved in “HSD-induced IL-17A production in γδT cells” will also be helpful in future research.
The researchers did acknowledge that high-salt diets might affect depression somewhat differently because of the behavior they observed in mice when the high-salt diet and chronic restraint stress components were combined.
It was different than when the mice only experienced the depressive behavior brought on by chronic restraint stress. They noted that “this suggests that there might be alternate effects of HSD or the combined treatment on depression-like behavior.”
This study emphasizes another potential reason why minimizing salt intake is a good thing, as it could offer benefits for mental health in addition to the noted physical health benefits.
As noted by the
Registered dietitian nutritionist Karen Z. Berg, MS, RD, CSO, CDN, not involved in the recent study, explained to MNT that: “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 further noted the importance of seeing sodium consumption in a realistic way because amounts can often get confusing:
“The Dietary Guidelines for Americans recommends 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. In order for an item to be classified as ‘low-sodium,’ it has to have 140 mg of sodium or less per serving. Don’t be fooled by labels that say ‘less sodium’. That does not mean low sodium, it just means that it has less than the original.”
