Choosing the Best Approach for Salt Reduction
Salt reduction is one strategy that is widely recommended to reduce high blood pressure and the cardiovascular complications associated with it. Sodium, the mineral in salt responsible for high blood pressure, is essential and needed to regulate blood volume, blood pressure, maintain an equilibrium in dissolved mineral concentrations within and between cells, and other functions. Almost everyone consumes more salt than is needed for these vital functions. Salt intakes are on average too high and are a contributor to hypertension, heart attacks and stroke.
Like many public health issues, there is some friction between “personal” versus “environmental” measures to reduce excessive salt intake. Individuals all have different baseline diets, food preferences and health status. Genetics can influence how blood pressure will react to a low-salt diet (Felder et al.). The effectiveness of education about the role of salt in the diet will vary depending on personal interest in health. Many people consume food that has not been prepared from scratch by themselves or someone else with a vested interest in their health and salt consumption, therefore they may have limited control over the salt content of their diet. Salt is used in many foods to enhance flavor, improve consistency, and to prevent growth of undesirable microorganisms. There are ways to reduce salt content in the diet without impacting taste or health, however, and the role of industry in helping to reduce the salt supply is one avenue that has received considerable attention. A voluntary initiative in the US called the National Salt Reduction Initiative has used this approach, the EU has a salt reduction campaign to reduce salt consumption in many types of foods, and some consumer organizations such as the Consumentenbond in the Netherlands, the Center for Science in the Pubic Interest in the US, and the Australian Division of World Action on Salt and Health in Australia have public awareness campaigns that highlight the role of industry in helping limit salt levels in food.
In a recent study, researchers Hendriksen and colleagues looked at the effects of various means of reducing salt consumption. They used three models:
1) The effect of actions by individuals in reducing the salt content of their diet, assuming that everyone substitutes the foods they eat for a similar item with the lowest salt content.
2) Reducing the salt content in processed foods, which varied depending on the type of salt reduction possible for each food type. On average, salt content was halved.
3) High salt consumers were assumed to be able to reduce the salt content of their diet to less than 6 grams per day.
The authors used data from the Dutch National Food Consumption Survey from 2007 to 2010 to estimate salt intakes and the relative contribution from the foods consumed. In the model, the authors assumed a larger decrease in blood pressure in hypertensive individuals compared to people with healthy blood pressure. The authors found that the first scenario reduced average salt consumption the most, by around 3 grams per day, and this would result in an overall blood pressure reduction of 1.9 mm Hg for systolic blood pressure. Reducing salt in processed foods would decrease salt intakes by 2.3 grams per day and lead to overall reductions in blood pressure of 1.5 mm Hg systolic, whereas capping salt intakes at 6 grams per day would reduce intakes by 2.5 grams per day and reduce blood pressure by 1.6 mg Hg systolic. These amounts do not seem large compared to individual recommendations to reduce blood pressure, however on the population level, they are significant. In the Dutch population of close to 17 million, the scenarios would prevent between 80,000 to 100,000 heart attacks, strokes and cases of congestive heart failure, and reduce all-cause mortality by 20,000 to 25,000 over 20 years. There would be an increase in DALYs for a 40-year old of 0.5%.
These results sound encouraging, however they could be considered “best case scenarios”. Not all people would be able, willing, or concerned enough to choose the lowest salt options of foods in the first model. The current voluntary model of salt reduction in the Netherlands has not resulted in a decrease in salt consumption over the last six years (Consumentenbond), and therefore it is unlikely that salt reduction by an average of 50% is achievable without mandatory policies in place. Even capping salt intakes of high salt consumers would require changes in individual behavior; there are reasons why people consume too much salt and people are unlikely to change without a reason that they find convincing.
Although reducing salt consumption in populations is attractive to reduce ill health, the translation of this ideal is challenging. Actions taken to help individuals choose a low salt diet, and at the same time to reduce the amount of salt in the food environment are likely to be the best policy to achieve these potential improvements in health.
Hendriksen MA, Hoogenveen RT, Hoekstra J, Geleijnse JM, Boshuizen HC, van Raaij JM. Potential effect of salt reduction in processed foods on health. The American Journal of Clinical Nutrition. 2014. http://ajcn.nutrition.org/content/early/2013/12/11/ajcn.113.062018.abstract
De Consumentenbond. Groot zoutonderzoek: 150 dagelijkse levensmiddelen. 2013. http://www.consumentenbond.nl/campagnes/opzouten/zout-test/
Felder RA, White MJ, Williams SM, Jose PA. Diagnostic tools for hypertension and salt sensitivity testing. Curr Opin Nephrol Hypertens. 2013 Jan;22(1):65-76. doi: 10.1097/MNH.0b013e32835b3693. http://www.ncbi.nlm.nih.gov/pubmed/23197156