There is of course a well-known relationship between sodium chloride and hypertension and we all make comments when we see the enthusiastic application of table salt onto food or add in the making of food. These are the visible uses of this flavour enhancer, but it is the salt used in food manufacturing that represents the largest exposure for most people.
A recent paper out in Nov 2010 in the BMJ Heart & Education explores the painfully slow progress towards suitable reductions. Many countries do recommend restricting daily sodium intake to 100 mmol (approximately 6 g of table salt) or less, but in a recent review of world salt levels, only seven out of the 25 countries reviewed met this goal suggesting a lack of legislative pressure and social interest.
In countries in which a western style diet is consumed some 75% of all ingested salt comes from food processing techniques. We all recognise that our initial enthusiasm with clients and patients for total salt reduction can reduce consumption through immediate changes in behaviour, but this is attenuated over time making what little gains in BP that were initially achieved too small to impact on significant numbers of the population.
Many countries, including Finland, the USA, the UK, Canada, France, Australia and New Zealand, have implemented salt reduction programmes based on product reformulation, labelling and/or public education to inform and encourage change in individual dietary choices and food industry practices. The population health benefits, however, are largely unknown except in Finland where the use of a replacement salt was made part of public health policy and included; Potassium, half the sodium of normal table salt and, more importantly, adds magnesium, potassium, lysine and iodine.
Adherence to antihypertensive drug therapy has been quite good. However, the drug treatment does not seem to account for more than 5-6 % of the observed fall of blood pressure, and 10-15 % of the decrease in deaths from strokes and ischaemic heart disease. The report went on to note that during the same time period …marked increases in the intake of alcohol, obesity among men, and smoking among women have been observed.
A follow up review noted that during the past 30 years, the one-third decrease in the average salt intake has been accompanied by a more than 10-mm Hg fall in the population average of both systolic and diastolic blood pressure, and a 75% to 80% decrease in both stroke and coronary heart disease mortality in Finland.
These are impressive improvements in mortality for a single intervention – if this was been achieved by medication the results would be lauded from all points of the media. Salt replacement may not be sexy but reducing sodium and increasing potassium in the diet has a dramatic impact on cardiovascular outcomes and represents the single most effective public health policy anywhere.
Overall, Cobiac and her colleagues calculated, 610,000 disability-adjusted life years could be avoided over the course of the lifetime of the population if everyone reduced their salt intake to recommended limits.
Salt Reduction is better than Cholesterol, Smoking and Weight Loss
Simulations in the USA even suggest that achieving a salt reduction of 3 g/day in the American diet (approximately 29% of daily intake for men and 41% for women) could benefit public health more than targeting tobacco, weight loss or cholesterol levels, and prevent as many deaths as antihypertensive drugs would prevent if given to everyone with hypertension.
It is not clear, however, if salt reductions of this magnitude are achievable with current measures that rely on voluntary changes by food manufacturers and informed choice by consumers.
Salt is added to processed foods for many reasons; to entice further consumption, to bulk a product up cheaply by increasing water-holding capacity, or to promote drink sales by increasing thirst. The idea that an alternative to salt may prevent CV disease by an amazing 75-80% suggests that the food industry looking to add value to their products would do well to exchange this ingredient quickly and the national government may be persuaded to seek legislation not to add or fortify as with folic acid, but to remove an ingredient closely linked to poor health and reduce the enormous economic burden related to CV disease.
 Law MR, Frost CD, Wald NJ. By how much does dietary salt reduction lower blood-pressure? 1. Analysis of observational data among populations. BMJ 1991;302:811–15. View Abstract
 Mohan S, Campbell NRC, Willis K. Effective population-wide public health interventions to promote sodium reduction. Can Med Assoc J 2009;181:605–9 View Abstract