The study from Queen Mary is one of three published today on bmj.com, which together suggest that cutting salt intake, while also increasing potassium levels in the diet, could have significant health and cost benefits worldwide.
Such a strategy will save millions of lives every year from heart disease and stroke, say experts.
The study from Queen Mary examined the effects of modest salt reduction on blood pressure, hormones, and blood fats (lipids) from 34 trials involving over 3,000 adults.
The researchers found a modest reduction in salt for four or more weeks led to significant falls in blood pressure in people with both raised and normal blood pressure. The effect was seen in white and black people and in men and women, thereby reducing strokes and heart attacks, the most common cause of death and disability in the UK.
The results showed that larger reductions in salt intake lead to larger decreases in blood pressure, prompting the authors to say that while current World Health Organisation recommendations to reduce salt intake from 9-12 to 5-6 g/day will have a major effect on blood pressure, a further reduction to 3 g/day should become the long term target. In the UK, NICE recommends a reduction in salt intake to 3 g per day by 2025 for the adult population.
Similar results to those in the Queen Mary paper were found in a second analysis of 56 studies also published today at bmj.com, which found that reduced salt intake lowers blood pressure and has no adverse effect on blood lipids, hormone levels, or kidney function.
A third study analysed data on potassium intake and health from 33 trials involving over 128,000 healthy participants. Potassium is found in most fresh fruits and vegetables and pulses. The results show that increased potassium intake reduces blood pressure in adults, and the researchers suggest an increased benefit with simultaneous reduction in salt intake.
Graham MacGregor, Professor of cardiovascular medicine at the Wolfson Institute of Preventive Medicine, part of Queen Mary, said: “These studies show that it is absolutely vital that the government forces the food industry to gradually reduce the amount of salt they add to our food by setting new targets.
“80 per cent of our salt intake is already hidden in food, i.e. the majority of consumers have no choice. If the food industry does not cooperate then the government must legislate, as has occurred in other countries (Portugal and South Africa).”
He FJ, Li J, MacGregor GA. Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. BMJ 2013;346:f1325 doi: 10.1136/bmj.f1325.
View this paper on bmj.com here
Professor Graham MacGregor if Chair of Consensus Action on Salt & Health (CASH). For more information on CASH visit www.actiononsalt.org.uk
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