Rat study suggests that salt may reduce anxiety

By Rebecca Coxon

A new study by researchers in Israel has suggested that ‘high salt intake may be adaptive in coping with daily adversity’.

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.

As someone who resolutely shies away from extra salt on anything (fish and chips a few times a year is the only exception!) this news has made me think twice about why we crave salt in our diets and whether it actually has any positive health implications.

Author of the study, Professor Micah Leshem, from the department of psychology at the University of Haifa, Israel, set out to investigate ‘the effect of low dietary sodium in models of depression and anxiety, on chronic mild stress (CMS), and on acute unpredictable stressors.’

They found that ‘low dietary sodium exacerbates anxiety in the elevated maze and open field.’ However, it ‘did not exacerbate modelled depression or anxiety in chronically and acutely stressed rats.’

The results of the study therefore indicate that low levels of salt in the diet may contribute to anxiety and help explain our persistent appetite for salty foods.

A salt loving nation

Sodium Chloride (or salt as it is better known) 'is vital for controlling the amount of water in the body, maintaining the normal pH of blood, transmitting nerve signals and helping muscular contraction,’ according to the BBC Health website.

However, before you reach for the salt shaker or microwave meal thinking it will lower your stress and anxiety levels, there are still the ever-reported risks in consuming too much of the stuff. Almost all processed foods contain added salt, so we really know how much we are consuming on a daily basis and what we should be?

The recommended maximum daily intake is 6g (or one teaspoon) but current average intake is 9g per day, over 50% higher than what is recommended for good health. According to doctors we are vastly overcosuming the addictive mineral as a nation: ‘Sodium, unlike all other minerals, is generally overconsumed, with the dietary intake of salt in the UK being far in excess of the recommended daily requirement,’ said BBC Health.

Professor Leshem who led the rat study, 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 also 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.’

Persistent appetite for salt

‘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.

The report concluded by asserting that such ‘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.’ And so the research continues.