March 3, 2015

expert reaction to high-salt diet and infections in mice

A study published in the journal Cell Metabolism has suggested that a high salt concentration in the skin may be beneficial in fighting infection, through activation of cells important in immune function.

Prof. Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:

“Salt has been valued as a food preservative for thousands of years to such an extent that the word ‘salary’ is derived from the payment in salt given to Roman soldiers. Brine was also known to promote wound healing. The findings of this new study in mice which show a protective effect of high salt diets on infection are interesting as they provide an additional reason why diets high in salt became popular in the Far East. However, for people living in the UK the benefits of a low salt intake outweigh any potential benefits of a high salt intake because cardiovascular disease is a major cause of death in older people whereas Oriental sore, which salt might protect against, is rarely if ever encountered.”

Dr Tim Chico, Reader in Cardiovascular Medicine and Consultant Cardiologist, University of Sheffield, said:

“This fascinating study shows that mice, and possibly humans, may use salt as a weapon against infections. It highlights the fact that many processes in our body can be either helpful or harmful depending on the situation we find ourselves in. If you cut yourself, you will be glad of the processes that lead to blood clotting to stop bleeding. However, these same processes can cause heart attacks and strokes, so blood clotting is both a good and bad thing depending on whether you are more likely to cut yourself or suffer a heart attack.

“We know a high salt diet causes high blood pressure (which will affect 90% of people in the UK) whereas serious skin infections are thankfully rare and usually easily treated. For these reasons, a high salt diet is more likely to harm than help, as the authors of this study point out.

“Now we know that salt can help fight off infections in some circumstances, there may be ways other than a high salt diet that help poorly healing skin infections. It may turn out rubbing salt into a wound is kinder than we thought.”

Prof. Nigel Brown, President, Society for General Microbiology, said:

“This is an interesting paper, although some organisms, such as Staphylococcus aureus, have been shown to have increased biofilm formation in the presence of sodium and increased penicillin resistance in the presence of chloride. High salt may therefore lead to an increase in pathogenic potential and antibiotic resistance. Much more work needs to be done before higher salt intakes can be recommended for therapeutic purposes.”

‘Cutaneous Na+ storage strengthens the antimicrobial barrier function of the skin and boosts macrophage-driven host defense’ by Jonathan Jantsch et al. published in Cell Metabolism on Tuesday 3 March 2015. 

Declared interests

Prof. Tom Sanders is a Scientific Governor of the charity British Nutrition Foundation and honorary Nutritional Director of the charity HEART UK.