Low salt diet may increase anxiety levels, suggests rat study

By Nathan Gray

- Last updated on GMT

Related tags: Salt intake, Psychology

Low levels of salt in the diet may contribute to anxiety and help explain our persistent appetite for salty foods, indicates a new study on rats.

The study, published in the journal Physiology & Behavior​, suggests that our high appetite for salty foods may be associated with coping with stress, depression and anxiety.

Author of the study, Professor Micah Leshem, from the department of psychology at the University of Haifa, Israel, noted that it has been suggested that the human need for high​salt intakes “may be adaptive in coping with daily adversity.”

“Therefore, we investigated the effect of low dietary sodium in models of depression and anxiety, on chronic mild stress (CMS), and on acute unpredictable stressors,”​ said Prof. Leshem.

“The psychological dimensions of salt intake are only now being addressed experimentally, and the ramifications for its control, and for individuals vulnerable to depression or stress, require clarification,”​ he added.

The study was funded by grants from the University of Haifa and the US Salt Institute.

Study details

Leshem reported that dietary sodium intake of 0.04 per cent (the equivalent of 3 grams per day salt intake in a 70 kg man) slightly reduces body weight, increases adrenal and heart weight, and increases mortality to 55 per cent in rats.

He added that, despite its minimal effect on growth, the sodium deficient diet “exacerbated measures of anxiety, specifically decreasing time, activity, and the ratio of activity.”

The research findings showed that high salt intake may be an adaptive response for coping with adversity, finding that low dietary sodium induces anxiety in rats.

However, Leshem said that rats with induced chronic mild stress (CMS) were found to reduce salt intake by 1.5 per cent. He noted that this reduction is specific to depression “insofar as it did not occur after repeated acute stressors. The reduction occurred despite sodium restriction.”

“Thus while sodium restriction is anxiogenic ​[induces anxiety], it does not exacerbate pre-existing depression or anxiety,”​ he added.

Salty appetite

Leshem noted that it is commonly believed that salt intake is required solely to maintain mineral-fluid balance, and that its excessive intake poses a risk to human health. However, he added that the determinants of human salt intake, in “excess and persistence, are unknown.”

“We do not know why heightened salt appetite persists, why it is so ubiquitous, nor why it is so in the face of [...] health risks and the social pressure to moderate intake ... Hence, there must be additional causes maintaining high salt intake,”​ wrote Leshem.

Source: Physiology & Behavior
Volume 103, Issue 5​, Pages 453-458, doi: 10.1016/j.physbeh.2011.03.025
“Low dietary sodium is anxiogenic in rats”
Author: M. Leshem

Related topics: Science, Reformulation

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