SALT is safe to eat – and cutting our daily intake does nothing to lower the risk of suffering from heart disease, research shows.
For years, doctors have been telling us that too much salt is bad and official NHS guidance aims to speed up new measures to control how much we eat.
But now a study, using more data than ever before, shows although blood pressure reduced when salt intake was cut, this had no long-term health benefits.
It is welcome news for those who love their fish and chips with a dash of salt and vinegar.
High levels of salt have long been said to lead to a greater risk of high blood pressure, heart attacks and strokes.
Guidance from the National Institute for Health and Clinical Excellence (Nice) has called for the speeding up of salt reduction measures, cutting the intake of salt from 6g a day per adult by 2015 to 3g by 2025.
Nice claims up to 40,000 deaths from heart disease and strokes could be prevented by changes to lifestyle.
Salt
But in a blow to that advice, this review has shown slashing our daily intake is not as beneficial as thought. People who cut the salt they ate by a small amount saw their blood pressure reduce after six months.
Professor Rod Taylor, from the University of Exeter, whose research is published in the latest edition of The Cochrane Library, said: “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.
“What we wanted to see was whether this dietary change also reduced a person’s risk of dying or suffering from cardiovascular events.”
Most studies recommended a reduction of 50 per cent of normal salt intake. A person’s daily salt intake from the research papers reviewed was on average 8-9g a day, so the reduction was to around 4g.
But this then had no long-term health benefits that may usually be expected from eating less salt.
The team reviewed seven studies that looked at 6,489 people, which they said was a large enough set of data from which to draw conclusions. Most experts say too much salt has detrimental health effects and cutting your intake can have beneficial effects in people with normal and high blood pressure but Prof Taylor said he could not find enough evidence for the theory.
He said: “We believe that we didn’t see big benefits in this study because the people in the trials we analysed only reduced their salt intake by a moderate amount, so the effect on blood pressure and heart disease was not large.”
His finding led him to call for health professionals to find more effective ways of reducing salt intake that are practical and inexpensive.
Prof Taylor said: “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.”
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Some will no doubt take the news with a pinch of salt.
But researchers claim that salt is addictive in the same way as cigarettes or hard drugs, with the craving triggering the same genes, brain cells and brain connections.
The finding could help explain why many find it so hard to cut back on salt, despite warnings about dangers to blood pressure and heart health.
For the study, Australian and American scientists kept some mice on low-salt diets and gave others a salt drip.
Activity in the creatures’ brains was then compared with that in mice fed normally. They also studied the brains of mice that had been starved of salt for three days and then given salty water to drink freely.
When the rodents were in need of salt, brain cells made proteins more usually linked to addiction to substances such as heroin, cocaine and nicotine.
Professor Derek Denton, of the University of Melbourne, said: ‘In this study we have demonstrated that one classic instinct, the hunger for salt, is providing neural organisation that subserves addiction to opiates and cocaine.’
The study also revealed that after salt was taken, the brain believes it has received its fix well before it should be physically possible.
In other words, the changes caused by salt cravings disappeared well before the salt could have left the gut, entered the blood and got to the brain.
Professor Denton said: ‘It was amazing to see that the genes that were set “off” by the loss of sodium were already beginning to get back to the original state within ten minutes.
‘It is an evolutionary mechanism of high survival value because when an animal is depleted of water or salt it can drink what it needs in five to ten minutes and get out which makes it less susceptible to predators.’
The researchers said that the importance of salt to overall health means that cravings for it form ‘an ancient instinct’ deeply embedded in the brain. This may explain why we find salty foods so tasty.
Experiments also revealed that stopping the mice from getting a feeling of pleasure from eating salt partially quenched the animals’ appetite for the condiment, the journal Proceedings of the National Academy of Sciences reports.
Dr Wolfgang Liedtke, of Duke University in North Carolina, said: ‘We were surprised and gratified to see that blocking addiction-related pathways could powerfully interfere with sodium appetite.’
The average Briton consumes 8.6g of salt a day – way above the recommended limit of 6g.
A recent University of Exeter study of almost 6,500 people concluded there was ‘no strong evidence’ that lowering levels in the diet reduced the risk of heart disease or premature death.
In fact it found that cutting back on salt actually raises the likelihood of death in some patients with heart problems.
However, health campaigners said this was because salt reduction needs to be over a longer period than the study monitored to have an impact.
Moderate cuts to salt intake don’t reduce the risk of developing heart disease or dying prematurely, a new review concludes.
Cutting back on salt did seem to reduce blood pressure slightly after more than six months but the British review of seven studies on nearly 6,500 participants did not find evidence of an effect of reducing salt intake on mortality or heart disease.
“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,” said the study’s lead author Prof. Rod Taylor of the Peninsula College of Medicine and Dentistry at the University of Exeter.
To see any clear health benefits, Taylor estimated he would need data from at least 18,000 people.
Taylor suggested that health practitioners need to find more effective ways of reducing salt intake that are both practicable and inexpensive.
Robert Walker from the School of Medicine at the University of Otago in New Zealand said lowering salt intake can reduce blood pressure.
“However, blood pressure is not the only cardiovascular risk and therefore it has to be seen in the global context of reducing risk not as the sole intervention to reduce heart attacks,” Walker told the Australian Broadcasting Corporation.
High blood pressure, or hypertension, is a major risk factor for cardiovascular diseases such as heart failure, heart attacks and stroke.
Canada’s Sodium Working Group agreed to set a goal of reducing sodium in the Canadian diet to 2,300 mg per day by 2016. That represents a five per cent reduction per year, based on the current average sodium intake of about 3,400 mg per day.
The study was published Wednesday by the Cochrane Library and appears in the Wednesday’s online issue of the American Journal of Hypertension.