A new study led by the University of Otago has deepened our understanding of the detrimental effects of excessive salt consumption.

Salt levels similar to those currently consumed in the Western diet may lead to hardening of arteries, independent of blood pressure effects, say new results that “confirm the potentially detrimental effects of a high dietary salt intake”.

The study, published in the American Journal of Clinical Nutrition, deepens our understanding of the detrimental effects of excessive salt consumption, which has led to pressure on the food industry to reformulate foods with lower sodium content.

“We hypothesized that if dietary salt restriction improves arterial vascular tone and blood pressure, then the converse should also occur, ie, increased salt intake would lead to a deterioration in arterial vascular tone,” wrote the researchers, led by Dr Rob Walker from the University of Otago in New Zealand.

“Confirmation of these changes would provide further supporting evidence of a role of dietary sodium restriction in the outpatient management of hypertensive individuals,” they added.

In collaboration with scientists from Deakin University in Australia, and the University of Colorado in the US, the University of Otago researchers report that people with hypertension participating in a low salt intervention period experienced significant increases in blood pressure when the salt content of their diets was increased. In addition, a correlation between salt and pulse wave velocity (PWV), a measure of the stiffness of the arteries, was observed, suggesting an effect on vascular health independent of blood pressure.

The researchers noted that their study was relatively small (only 35 people participated) and short (four weeks) and therefore need support in longer trials with other populations, particularly those at high risk like the obese, diabetics, and people with kidney disease.

Despite such caveats, Dr Walker and his co-workers state that their findings “confirm the potentially detrimental effects of a high dietary salt intake, with increases in blood pressure and PWVevident within a short time frame”.

Salt – a little but not too much

Salt is of course a vital nutrient and is necessary for the body to function, but the average daily salt consumption in the western world, between 10 and 12g, vastly exceeds recommendations of 5 grams per day to control blood pressure levels and reduce hypertension prevalence and related health risks in populations.

And with 80 per cent of salt intake coming from processed foods, many countries have initiated salt reduction programmes, with many holding up the UK`s Food Standards Agency as the torch bearer for national initiatives.

The benefits of a global salt reduction strategy were given blinding clarity by a meta-analysis published in The Lancet Chronic Diseases Series in 2007, which concluded that reducing salt intake around the world by 15 per cent could prevent almost nine million deaths between 2006 and 2015.

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