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Moderate reductions in the amount of salt people eat doesn't reduce their likelihood of dying or experiencing cardiovascular disease. This is the main conclusion from a systematic review published in the latest edition of The Cochrane Library.
There is lots of evidence that reducing dietary salt intake reduces blood pressure and the researchers did see some indication of this occurring. "Intensive support and encouragement to reduce salt intake did lead to a reduction in salt eaten and a small reduction in blood pressure after more than six months," says lead author Professor Rod Taylor who works at the Peninsula College of Medicine and Dentistry at the University of Exeter.
"What we wanted to see was whether this dietary change also reduced a person's risk of dying or suffering from cardiovascular events," says Taylor.
An earlier Cochrane review of dietary advice published in 2004 could not find enough evidence to allow the researchers to draw any conclusions about the effects of reducing salt intake on mortality or cardiovascular events. In Taylor's newly published research, however, the team managed to locate seven studies that together included 6,489 participants. This gave a sufficiently large set of data to be able to start drawing conclusions. Even so, Taylor believes he would need to have data from at least 18,000 individuals before he could expect to reveal any clear health benefits.
Most experts are agreed that consuming too much salt is not good for you and that salt reduction is beneficial in people with normal and high blood pressure. "We believe that we didn't see big benefits in this study because the people in the trials we analyzed only reduced their salt intake by a moderate amount, so the effect on blood pressure and heart disease was not large," says Taylor. He believes that health practitioners need to find more effective ways of reducing salt intake that are both practicable and inexpensive.
Many countries have government-sanctioned recommendations that call for reduced dietary sodium. In the UK, the National Institute of Health and Clinical Guidance (NICE) has recently called for an acceleration of the reduction in salt in the general population from a maximum intake of 6g per day per adult by 2015 to 3g by 2025.
"With governments setting ever lower targets for salt intake, and food manufacturers working to remove it from their products, it's really important that we do some large research trials to get a full understanding of the benefits and risks of reducing salt intake," says Taylor.