Population-level interventions in government jurisdictions for dietary sodium reduction

In almost all countries worldwide, most people eat too much salt. This is a problem because eating too much salt can cause high blood pressure, which can lead to health problems such as heart disease and stroke. To reduce the amount of salt eaten, governments in many countries have developed national salt reduction initiatives.

This review aimed to examine whether national salt reduction initiatives have been effective in reducing the amount of salt consumed in those populations.

 The authors searched research papers and government reports and had direct communication with individuals working in salt reduction in their respective countries. The evidence is current as of 5 January 2015, when they last searched electronic databases. Initiatives in 15 countries met the inclusion criteria. Ten of these countries provided sufficient data for quantitative analysis, gathered from studies that included 64,798 participants. Initiatives ranged from one activity (e.g. in Japan, which at the time of writing had a public information campaign) to many activities (e.g. in the United Kingdom, which provided five activities including on-package nutrition information, restrictions on marketing to children and food product reformulation). Of the 15 countries that met inclusion criteria, seven provided information about funding source, of which six reported non-industry funding. The other eight countries did not report a funding source for one or more data point(s).

Five of the 10 countries included in the quantitative analysis (China, Finland, France, Ireland and England) showed a decrease in salt intake after the intervention. Two of the 10 countries (Canada, Switzerland) showed an increase in salt intake after the intervention. Because the initiatives were very different, the authors cannot present an overall finding of whether these types of initiatives work.

When they focused on the subset of seven countries whose salt reduction initiatives included multiple components and were not focused solely on educating the public, the authors found that more than half (four of seven) showed a decrease in salt intake from pre-intervention to post-intervention.

When the nine initiatives that analysed men and women separately were examined, it was found that amongst men, more than half (five of nine) showed a decrease in salt intake after the intervention. Amongst women, the pattern of findings was less clear, with three of nine interventions showing a decrease, two showing an increase and four showing no change in salt intake.

Low-bias study designs, such as randomised controlled trials, typically are not suitable for evaluating complex initiatives such as these; therefore, the authors rated all of the studies included in this review as having low methodological quality. Large nationally representative samples of the population and careful measurement of dietary sodium intake were strengths of several studies. However, because of study design limitations, the trustworthiness of study results is not clear.

Overall, these results show that national government initiatives have the potential to achieve population-wide reductions in salt intake, especially amongst men, and particularly if they employ more than one strategy and include structural activities such as food product reformulation (i.e. food companies putting less salt in food products). The wide variation of results across the studies presents a challenge in interpreting the current evidence and this warrants more research to help further understand this.

To learn more, read the review.