Key article & video: Scant Evidence That Salt Raises BP, Review Finds
During our second Food and Health Group meeting, Caroline was demonstrating how to make lacto-fermented veggies. When she added a couple of tablespoons of salt to the mix that was going into the jar several people expressed their discomfort: Surely so much salt is bad for you?
We’ve all been told that one haven’t we? The media continually cry “Salt increases blood pressure” and “Food manufacturers are under pressure to reduce salt in food”. It is trotted out as if the scientific evidence is overwhelming, as if only a fool would question it. It may come as a surprise then to learn that the evidence for harm from salt is very underwhelming.
When, in 2011, the Cochrane Review published two studies finding little or no relationship with all-cause mortality and salt reduction, they received criticism from many scientists including the Lancet, who said “They have seriously misled the press and thereby the public.” Now lets just stop a minute and consider what is being said here. Policy makers are telling us we should reduce salt intake to avoid health issues. But the studies do not support this. As the Cochrane reviewers state:
“After more than 150 randomized controlled trials 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 Cochrane Collaboration was set up to ensure that systematic reviews of scientific studies were carried out without the typical bias that plagues meta-analyses. They throw out poorly designed studies and base their conclusions on the strength of what the best quality studies show. The fact that they had 150 gold-standard (randomised controlled) trials in the review is testament to how much good science has actually been done on this subject. The fact that they found ‘no signal’ – i.e. no overall evidence – should be the nail in the coffin for this long-standing and persistent myth.
So how come that this review did not make the news headlines in 2011? How come that a year later, an article called ‘Global health report card’ (New Scientist 22/29 Dec 2012) states that “Increasing salt intake is partly to blame for rising blood pressure around the globe”? Why do the media, GPs and the NHS (who have the gall to write ‘Salt: the Facts’ whilst ignoring the Cochrane review) carry on as if the benefits of salt reduction are well established? Probably because it is no longer a meer scientific question, but has become part of global public health policy – an entirely different beast! When my son studied media and film at college he was told in no uncertain terms that the news industry always prioritise stories which the public already believe over ones that they do not. Because the authorities have been saying ‘salt is bad’ for so long, and have just about everyone singing from the same hymn sheet, no one wants to be the first to perform the about-face. They have too much credibility to lose.
Fortunately, the professional medical research media are less constrained by public opinion and policy as they are largely only read by other medical professionals. In this day of the internet, fortunately, we can all read what they are saying. So if you want to get informed, you could start, with this Medpage Today article, which covers the debate, and includes a short video. The long and the short of it? Salt reduction may be beneficial in some patients with uncontrolled hypertension. For the rest of us, the evidence suggests it’s a non-issue.
Salt has been revered for millenia. So valuable was it in Roman times that soldiers were even paid in salt – it is where our word ‘salary’ comes from. Animals too, have been known to go to extreme lengths to get salt when it is insufficient in their diets. The clip below shows how dozens of herbivores make their way to a salt cave to gain this life saving nutrient.
What is not often mentioned are the dangers of lowering salt intake. For example, the production of stomach acid (hydrochloric acid) is dependent on the chloride ion which sodium chloride (salt) can provide. If sodium levels are too low this also will prevent gastric acid production. Following kidney problems, diarrhoea, surgery or when large quantities of fluid are lost adequate salt intake is essential (as demonstrated by the use of saline drips). Bile acids – necessary for digestion – are formed with sodium.
Rock salt and sea salt
It makes sense to use the most nutritious materials in all of our cooking, so I recommend a good quality rock salt or sea salt. They contain trace minerals besides the sodium chloride you get in ordinary table salt, including, for example, iodine, and unlike common table salt usually do not contain added flow agents.