The 15 per cent fall in dietary salt intake over the past decade in England is likely to have had a key role in the 40 per cent drop in deaths from heart disease and stroke over the same period, according to research published in the journal BMJ Open.

But average dietary salt intake across the nations is still “far too high”, warned the authors, who are from the Wolfson Institute of Preventive Medicine, Barts and the London School of Medicine and Dentistry, Queen Mary University of London. They said a “much greater effort” was needed to curb salt content of the foods people eat.

Dietary salt is known to increase blood pressure, which is itself a major risk factor for heart disease and stroke.

Study method

The authors of the BMJ Open paper based their findings on an analysis of data from more than 31,500 people taking part in the Health Survey for England. Data was collected in 2003, 2006, 2008 and 2011, with the initiative to curb population salt intake having begun in the UK in 2003.

The survey involved a random representative sample of the adult population of England living in private households, and included information on diet and blood pressure measurements.

The average population salt intake was calculated from urine collected over a 24-hour period in almost 3,000 people who were part of the National Diet and Nutrition Survey between 2003 and 2011. This survey involved random samples of the population.

During this period, nationally collated figures showed that stroke deaths in England fell by 42 per cent, while deaths from coronary heart disease dropped by 40 per cent.

Similarly, the prevalence of several risk factors for cardiovascular disease also fell, including average cholesterol, blood pressure, and smoking. Weight (Body Mass Index), however, rose. Fruit and vegetable consumption also rose slightly.

With the exception of increasing weight gain, all these trends, along with better treatment of cardiovascular disease and its risk factors, would have probably contributed to the dramatic falls in stroke and heart disease deaths, explained the authors of the study.

The authors cautioned that they used several sets of data, involving different people, so were not able to track changes at the individual level, nor were they able to account for physical activity levels.

Salt reduction influence

Daily salt intake fell by an average of 1.4g during this period, amounting to a drop of 15 per cent. Among those not taking blood pressure lowering medications, average blood pressure also fell by 2.7/1.1mm Hg, even after taking into account other influential factors.

Although salt was not measured in this particular group, the substantial fall in salt consumption in the population samples suggested that the decrease in blood pressure could largely be attributable to less dietary salt rather than to medication, the authors said. They said that previously published research suggests that the contribution of blood pressure lowering medications to population falls in blood pressure is relatively small.

The researchers said the reduction in salt intake was likely to be “an important contributor” to the falls in blood pressure in England from 2003 to 2011.

“As a result, the decrease in salt intake would have played an important role in the reduction in stroke and ischaemic heart disease mortality during this period,” the authors wrote.

More effort to reduce salt intake needed

However, the authors said that despite “considerable progress”, 70 per cent of the adult population was still eating more than the recommended 6g of salt per day, with 80 per cent of intake coming from processed foods.

“Therefore, continuing and much greater efforts are needed to achieve further reductions in salt intake to prevent the maximum number of stroke and heart disease deaths,” the authors wrote.

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