The review’s authors, from Denmark’s Copenhagen University Hospital and Bispebjerg University Hospital, examined randomized controlled trials (RCTs) that sought to estimate the effect of a low-sodium diet on blood pressure, as well as certain hormones, cholesterol and/or triglycerides.
They found that although cutting sodium consumption did decrease blood pressure, it also tended to increase levels of hormones, cholesterol and triglycerides, which are all thought to be risk factors for heart disease.
"In my opinion, people should generally not worry about their salt intake," said lead author Dr Niels Graudal, senior consultant in internal medicine and rheumatology at Copenhagen University Hospital – a comment that was welcomed by the Salt Institute.
Reacting to the review, the organization’s vice president of science and research Morton Satin said: “Population-wide salt reduction is proving to be one of the biggest deceptions in modern public health."
Many studies have shown a link between salt intake and blood pressure – a major risk factor for heart disease – and this has led to pressure on food manufacturers to reduce sodium in their products. The Centers for Disease Control and Prevention has estimated that about 75% of the sodium in the average US diet comes from processed food, with cheese, bread, pizza and grain-based desserts some of the biggest contributors.
The review found that blood pressure was reduced by about 1% for white people with normal blood pressure on a low-salt diet, and about by about 3.5% for white people with high blood pressure.
The authors said that there was some data suggesting that Asians and blacks were more sensitive to sodium reduction than whites, but this required further study. They said future studies of mixed populations should report results separately according to ethnicity.
The authors concluded: “Long-term RCTs with mortality and morbidity outcomes would be desirable to determine whether the benefits of sodium reduction outweigh the harms. However, such studies may not be practicable and instead well-designed prospective population studies could be an alternative.
“After more than 150 RCTs and 13 population studies without an obvious signal in favor of sodium reduction, another position could be to accept that such a signal may not exist.”
The 167 studies involved in the review were conducted between 1950 and 2011.
The latest Dietary Guidelines for Americans recommend keeping sodium intake under 2,300mg per day – and under 1,500mg per day for those with high blood pressure, as well as those at risk of high blood pressure, including blacks and those aged over 50, groups that make up about 70% of the US population.
Meanwhile, the American Heart Association recommends all Americans should consume less than 1,500mg of sodium per day, while average US sodium consumption is about 3,400mg a day.
Source: The Cochrane Library
2011, Issue 11. Art.No.: CD004022. DOI: 10.1002/14651858.CD004022.
“Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol, and triglyceride”
Authors: Niels Albert Graudal, Thorbjorn Hubeck-Graudal, Gesche Jurgens