Salt, Diet, and Health

John Swales in his review of our book1Swales J Salt: sense and pseudo-consensus.Lancet. 1999; 353: 597-598Summary Full Text Full Text PDF Google Scholar declares an interest in that we state that in 1986 he disputed the relationship between salt intake and blood pressure at a press conference and he implies that to have done so is unremarkable. But he does not reveal that the press conference was funded and organised by the Salt Manufacturers’ Association in conjunction with Kingsway, a public relations company.2MacGregor GA de Wardener. HE Salt diet and health. Cambridge University Press, Cambridge1998Google Scholar They also set up a so-called Salt Data Centre that claimed to give impartial and independent advice on the relation between salt and blood pressure. The press conference was held in January, 1986, in London. Swales was the sole speaker: his solicited, unopposed, and commercially popular view received widespread media publicity.2MacGregor GA de Wardener. HE Salt diet and health. Cambridge University Press, Cambridge1998Google Scholar One of the major aims of the Salt Manufacturers’ Association is to protect the sale of salt, particularly that added to processed food, which accounts for about 40% by value of all salt sales, and to try and increase salt sales. The subsequent campaign developed by the Kingsway Rowland Company was so successful that it was used as an example on how to influence public opinion in the marketing for their company. Swales’ continued opinion that there is no consensus about the effects on blood pressure of a moderate permanent reduction in salt intake to around 100 mmol per day is based on a meta-analysis of extremely short periods of salt restriction, which resulted in a mean 24 h sodium excretion of 41 mmol/L for a median duration of 8 days in 2581 normotensives.3Graudal NA Gallo AM Garred P Effects of sodium restriction on blood pressure, renin, aldosterone, catecholamines, cholesterols and trigylcerides: a metaanalysis.JAMA. 1998; 279: 1383-1391Crossref PubMed Scopus (418) Google Scholar He regards this analysis as “the most rigorous systematic review of intervention trials” and concludes “that salt restriction in healthy people produces no worthwhile lowering of the blood pressure”. We agree that it may be the best review of what a few days of salt restriction can do to blood pressure. However, there was a highly significant mean fall in systolic pressure of 1·5 mm Hg which, if prolonged and on a population basis, would nevertheless have a major effect on reducing cardiovascular disease. But these short-term studies are utterly irrelevant to a discussion of the merits of a sustained, moderate reduction in salt intake on blood pressure that one wonders why they were introduced. There are huge commercial reasons for protecting the high salt content of processed food.2MacGregor GA de Wardener. HE Salt diet and health. Cambridge University Press, Cambridge1998Google Scholar It is not surprising, therefore, that some food and softdrink companies and the salt industry have fought a careful and largely covert campaign akin to the tobacco manufacturers suggesting there is a lack of consensus about the need to reduce our unnecessarily high salt consumption. Nevertheless, consensus that salt intake should be reduced in the whole population does now exist. For instance, in the UK, a Government-appointed expert committee on diet and cardiovascular disease reviewed all the evidence and unequivocally recommended a reduction in salt intake for the whole UK population from 9 to 6 g per day.4Nutritional Aspects of Cardiovascular Disease.Report on the Cardiovascular Review Group Committee on Medical Aspects of Food Policy (COMA). Department of Health and Social Subjects 46. HM Stationery Office, London1994Google Scholar Meetings at the British Heart Foundation in December, 1997, the National Heart Lung and Blood Institute in Washington in January, 1999, have all endorsed these population recommendations. Furthermore, Swales’ assertion that “If, on the other hand, there is a scientific consensus, as the authors claim, surely we have arrived at the stage of implementation” has been accepted. A recent UK Department of Health release states that “the Government accepts that there is a large body of authoritative opinion which favours a general reduction in salt intake. In consequence, Ministers have asked officials to initiate discussion with the Food Industry to explore the scope of broadening public choice in, and reducing the salt content of, manufactured food”.5Department of Health Press Release, Feb 23, 1999.Google Scholar Salt, diet, and healthAuthors' reply Full-Text PDF