Salt is bad for you, as we’ve been told for years and years. It raises your blood pressure and makes you more prone to strokes and other nasty health issues. Except … perhaps not:
The more salt we eat, the more water our body retains. This increases blood pressure, at least until our kidneys flush out the salt and water. Those who see salt as a problem believe that the effect on blood pressure is more lasting, and that if too much salt is ingested over a long period of time it will cause hypertension and perhaps death. A much-cited study carried out by America’s National Institutes of Health in 2001, called the DASH-sodium study, found that participants put on diets that were lower in sodium than the control group ended up with significantly lower blood pressure. This study forms the basis for many of the public-health pronouncements that demonise salt. America’s dietary guidelines, based on “a strong body of evidence”, put salt at the top of the list of things to avoid.
The body of evidence, though, is rather weaker than the American government lets on. The DASH study is one of many that have looked at the effects of salt intake on health. Others have failed to produce similar results. The English study mentioned above finds a correlation, but other factors — such as a simultaneous decline in smoking — seem more likely to account for the improved health outcomes. In 2011 two meta-analyses, which look at the results from many different studies, were published by the Cochrane Collaboration, a non-profit that reviews medical evidence. The first found that reducing salt intake leads to lower blood pressure, but concluded that there is “insufficient evidence” that this will lead to fewer premature deaths or a lower incidence of heart disease. The second concluded, rather simply, that “we do not know if low salt diets improve or worsen health outcomes.” The authors went on to say that “after more than 150 [randomised controlled trials] and 13 population studies without an obvious signal in favour of sodium reduction, another position could be to accept that such a signal may not exist.”
Some researchers go a step further, claiming that reducing salt intake actually increases a person’s risk of dying. The body needs some amount of sodium; if it gets too little the kidney secretes an enzyme called renin that can lead to hypertension. Some studies have found that low sodium levels were associated with increased risk of heart failure. Others suggest that a low sodium-to-potassium ratio may be the key to heart health. Much depends on the individual. The evidence is inconclusive, yet public-health officials have long presented the link between salt and heart disease as if it were fact. Such confidence is not warranted. There are plenty of reasons to avoid a full English breakfast, but salt may not be one of them.
