Mixing it up on the blogosphere
The Salt Institute has been engaged in the cyber-debate over the British Food Standards Agency's promotion of salt-reduced diets. FSA released a report yesterday stating that in five years, Britons had reduced their salt intake from 9.5 g/day to 9.0 g/day. A typical newspaper story ran the story this way:
Salt consumption in Britain is still on average 50 per cent higher than the recommended amount, new research has revealed today. Tests on 1,287 adults showed their average salt intake was 9g per day. Although this is adrop from 9.5g when the last tests were done in 2001, the consumption is far higher than the national target of 6g per day, the Food Standards Agency said.
That set off a string of reader comments -- you can read them yourself .
First of out the box was the accusation that salt manufacturers who object that the intervention might entail risks should "tell us which consumers could be harmed by a blanket approach and of course, the evidence?"
OK. We did. I responded:
Two groups come to mind, based on peer-review, published studies: the populations of Mr. Schmulian's Scotland and the population of the United States. The massive Scottish Heart Health study found additional risk for Scots and two studies of the US National Health and Nutrition Examination survey found 20% and 37% greater cardiovascular mortality among those consuming FSA-recommended amounts of salt.
The FSA contention of lower CV risk is based on extrapolations that have not been confirmed in studies of the direct question: will lower salt diets be healthier.
That's why the experts in evidence-based medicine at the Oxford-based Cochrane Collaboration have concluded there is insufficient evidence to recommend universal salt reduction.
That prompted another reader to complain "Your claim about the cochrane institute is wrong," adding that blood pressure is improved by salt reduction. To keep the record accurate and in further response, I added:
The Cochrane review "Advice to reduced dietary salt for prevention of cardiovascular disease" which the Cochrane Library issued in November 2003 (http://www.cochrane.org/reviews/en/ab003656.html ). It concluded:
"Intensive support and encouragement to reduce salt intake did lead to reduction in salt eaten. It also lowered blood pressure but ... not enough to expect an important health benefit. It was also very hard to keep to a low salt diet....
"There was not enough information to assess the effect of these changes in salt intake on health or deaths."
But, the question really isn't about blood pressure, it's about health outcomes. Blood pressure is an interim variable affected by salt. So is insulin resistance, plasma renin activity, sympathetic nervous system activity, etc. What we need to focus on is the net effect: are people healthier? living longer? having fewer heart attacks, etc?
Just keeping the science front and foremost.
