MEDICAL MATTERS:Dietary issue is crying out for more research, writes MUIRIS HOUSTON
‘YOU’RE THE salt of the earth”, “take it with a pinch of salt” and “salt it away for the future” are just some of the many references to salt in the vernacular. It’s a reflection of the central place of salt in previous centuries, from its use as currency to people’s dependence on it as a means of preserving fish and meat.
A visit to Romania in the late 1970s remains my first and only experience of a salt mine. If memory serves me, it was located in the centre of the country, near the industrial city of Ploeisti. We descended into the bowels of the earth in rickety wire cages – this was communist Eastern Europe after all – accompanied by plummeting temperatures. But there was no mistaking the clarity of the air as we walked around the massive salt chambers below. It made you want to breathe more deeply and more slowly, such was its purity.
I was reminded of this when reading about a new health vogue in the US. Halotherapy is the breathing in of microscopic salt particles in an effort to improve respiratory difficulties. There is no scientific evidence to support its use, but it is proving popular as an alternative therapy for asthma, allergies and colds.
It involves the creation of “salt rooms”, with the aim of replicating conditions found in east European caverns, where people sit for 45-minute periods breathing in particles blown in by a generator.
But specialists warn it should not be used for primary therapy and people certainly should not give up their medication in favour of halotherapy.
The principle may be similar to the use of nasal sprays and salt solutions to help decongestion.
So what is salt, and how can it affect our health? Salt contains sodium, one of the minerals essential for life. Our bodies need minerals for several reasons: they are part of its structure; they help regulate bodily fluids; and, as components of enzymes, they are involved in the body’s metabolic processes.
Some minerals, such as zinc, copper and manganese, are antioxidants; they play a role in stopping free radicals from damaging cells. The major minerals – calcium, potassium, phosphorous, magnesium and sodium – are needed in the largest amounts. Others, such as iron, iodine and copper, are required in smaller quantities, but they are no less important.
Different foods supply different minerals, which is why eating a varied diet is essential, although I was most interested to learn recently from a dietitian colleague that while the “lo-salt” version may have less sodium, to compensate it has higher levels of potassium, which poses its own health risks. In any event, most of our salt intake is via processed foods, so efforts to reduce it in our diets are probably best focused on a more careful perusal of the dietary information on food packaging.
Following its successful anti-passive smoking intervention, the New York City Department of Health has started a campaign to persuade the makers of processed food to reduce salt content by more than 40 per cent over the next 10 years. The premise is simple: if people eat less salt, it could lower blood pressure, and this should translate into fewer heart attacks and stroke.
Or is it? A recent review in the Journal of the American Medical Association found a low-salt diet was associated with fewer strokes and heart attacks in just five of 11 studies analysed; in the rest, people on a low-salt diet saw no change in clinical outcome or even fared worse. We do know that cardiac risk assessment works only when a multiplicity of factors are taken into account. And there may be other metabolic consequences of limiting sodium intake, such as increased insulin resistance and activation of a regulatory system in the kidneys, which may themselves add to the risk of heart attack and stroke.
The crux of the issue is that we have yet to complete a large randomised and double blind trial into the specific effects of a low-sodium diet. Most of the available evidence is based on observational research, which is good at identifying factors associated with a particular condition but is not designed to identify a cause and effect. Until we do, salt will remain under medical suspicion.
Maurice Neligan is stranded overseas