The research, published in the American Heart Association's journal of Hypertension (Vo. 48, pp. 861-869) looks set to increase pressure on the food industry to reduce salt content in a wide range of foods, particularly those aimed at children.
"We already know that a modest reduction of salt intake in adults causes very worthwhile falls in blood pressure but this new research now strongly supports the same policy of salt reduction in children," said lead author Dr Feng He, from St Georges University of London.
The meta-analysis combined results of ten trials with a total of 966 children and adolescents aged between eight and 16, and three trials studying a total of 551 infants. The well-defined inclusion criteria including the use of a control group and a duration of two or more weeks, with salt reduction as the only intervention.
Analysis of ten trials of children and adolescents (average age: 13 years; average duration: 4 weeks) revealed that a reduction in salt intake of 42 per cent produced significant decreases in blood pressure of 1.17 mm Hg (systolic) and 1.29 mm Hg (diastolic).
Analysis of the infant trials (average duration: 20 weeks) revealed that a reduction in salt intake of 54 per cent was associated with a significant drop in systolic blood pressure of about 2.5 mm Hg.
"This is the first meta-analysis of salt reduction in children, and it demonstrates that a modest reduction in salt intake causes immediate falls in blood pressure and, if continued, may well lessen the subsequent rise in blood pressure with age," wrote the reviewers, Feng He and Prof. Graham MacGregor.
"These results in conjunction with other evidence provide strong support for a reduction in salt intake in children," they said.
Prof. Graham MacGregor chairs both the newly formed World Action on Salt and Health (WASH) and Consensus Action on Salt and Health (CASH), both of which have been active in pressuring food companies into reducing dietary salt intake in order to lower blood pressure.
Yet not everyone agrees with the science behind WASH's claims. Robert Speiser, director of EuSalt, told FoodNavigator earlier this year that he strongly disputes the need for salt intake restrictions.
Speiser's concern is that some regulatory bodies, such as the FSA in the UK, focus on certain scientific studies and neglect others.
However, in an accompanying editorial (Hypertension, Vol. 48, pp. 818-819), Jeffrey Cutler and Edward Roccella from the Office of Prevention, Education, and Control, National Heart, Lung, and Blood Institute (National Institutes of Health), said that the researchers used state-of-the-art methods with sufficient tests for publication bias and appropriate sensitivity analyses.
"He and MacGregor present evidence that considerably strengthens the science base for (the recommendation that salt intake be reduced) and suggest that a primary prevention strategy based on dietary salt reduction, initiated in childhood, is capable of reducing exposure to an important cardiovascular risk factor," they said.
"This important public health strategy, designed to slow or prevent the rising arterial blood pressure that accompanies aging, complements clinical strategies in pursuit of the goal of improving national and international cardiovascular health, now and for generations to come," concluded Cutler and Roccella.
Jo Butten, nutritionist for CASH, welcomed the research. "The UK is leading the world in making reductions in the salt content of manufactured foods and some children's foods have had their salt content reduced, but sadly many other manufacturers are still stuffing salt into their products and marketing them to children. They need to take immediate action to reduce these unnecessary and very high salt concentrations."
In the UK, Ireland and the USA, over 80 per cent of salt intake comes from processed food, with 20 per cent of salt intake coming from meat and meat products, and about 35 per cent from cereal and cereal products.
However, Julian Hunt, director of communications for the Food and Drink Federation pointed out the progress the UK food industry has made in reducing salt in foods.
"CASH has recognised that UK food manufacturers have taken the lead on salt reductions. Consumers young and old are benefiting from enormous cuts in salt in a whole range of processed foods, and industry is committed to doing more," said Hunt.
"Industry has worked very closely with the Food Standards Agency to reduce salt in foods eaten by children such as bread, breakfast cereals and soups with other products such as potato crisps and biscuits also making tremendous cuts.
"Additionally, more and more manufacturers are helping consumers see at a glance how much salt is in their foods by putting information on the front of packs and including salt equivalence," he said.