The research was carried out jointly by the World Health Organization's Collaborating Center for Nutrition, based at the University of Warwick and University Hospital in Coventry, UK, and the European Society of Hypertension Excellence Center in Hypertension based at the Department of Clinical and Experimental Medicine, Federico II University Medical School in Naples, Italy.
The study looked at the relationship between the level of habitual dietary salt intake and the occurrence of stroke and cardiovascular disease by reviewing 13 prospective studies from the UK, Japan, USA, The Netherlands, Finland and China, including more than 170,000 participants, followed up for 3.5 to 19 years, who experienced nearly 11,000 vascular events.
The study provides unequivocal evidence of the direct link between high dietary salt intake and increased risk of stroke and cardiovascular disease. A 5 g lower daily salt intake would reduce stroke by 23% and total cardiovascular disease by 17%, thus averting 1.25 million fatal and non-fatal strokes, and almost 3 million vascular events worldwide each year. The effect is greater, the larger the difference in salt intake and increases with time.
Professor Francesco Cappuccio, Head of the World Health Organization Collaboration Center at Warwick Medical School said: "We have seen reductions in the salt content of several food items, due to the collaboration between governments, public health bodies and sectors of the industry on a voluntary basis. However, the progress towards the recommended targets has been slow. For population salt intake to approach the WHO targets within a reasonable time, a regulatory approach is necessary, in addition to health promotion campaigns, to reduce the burden of avoidable death, disability and associated costs to individuals and society caused by unacceptable high levels of salt in our diet".
"Habitual salt intake in most adult populations around the world exceeds 10 g per day", says Professor Pasquale Strazzullo, one of the senior authors, "and the World Health Organization recommends that daily intake should not exceed 5 grams. Our study supports current recommendations to reduce substantially salt intake worldwide to avoid unnecessary strokes and other cardiovascular events".
Most of the salt we eat comes from that added to food in the manufacturing process by industry, caterers and food producers.
Cardiovascular disease is the first cause of death and disability in the world among people aged over 60 years and the second one among those 15 to 59 years old.
According to the World Health Organization, 62% of all strokes and 49% of coronary heart disease events are attributable to high blood pressure.
There is a direct causal relationship between levels of dietary salt intake and levels of blood pressure.