The researchers, led by Dr Duncan Gillespie from the University of Liverpool, compared four different salt reduction methods – mandatory reformulation, voluntary reformulation, better nutrition labelling and public health campaigns.
Using data from Cochrane reviews, national health surveys and expert opinions, Gillespie et al. analysed each one for its efficacy - in other words the amount of salt that could be cut per day - its scope in terms of number of people affected, and impact in terms of preventing cardiovascular deaths.
For the mandatory reformulation scenario, they envisaged a 30% salt reduction, or 1.45 g of salt per day, which equated to an average of 4,500 lives saved a year.
Obliging companies reformulate was also the most inequality-reducing method, reaching an estimated 85% of people in the most deprived sections of society.
Gillespie said:"Unhealthy diets are concentrated in the more deprived parts of society and these groups are also at the greatest risk of disease, and so the problem with public health policy is making sure it reaches more deprived individuals."
Introducing mandatory salt reduction targets was the best way to do this – and previous research has suggested that it would also be the most cost-effective strategy, they wrote.
Voluntary reformulation, on the other hand, would save an estimated 1,500 deaths while improved nutrition labelling and public health campaigns would only save around 500 deaths per year as well as having a minimal effect on equality.
Effective – but ‘politically challenging’
Interventions which affect our food environment such as reformulation through legislation or ‘sin taxes’ - known as structural policies - tend in general to be more effective and inequality-reducing. But, wrote the researchers, they are also seen as ’politically challenging’.
Agentic options, on the other hand, rely on influencing individual choice - examples include social marketing and nutrition labelling.
"Agentic policy options are politically more likely, even though policymakers and academics agree that they have fewer benefits, and potentially widen inequality.”
"[They] might be a third as effective as voluntary reformulation, and a tenth as effective as our high impact mandatory scenario.”
Ultimately, however, the researchers said that best – and most realistic – strategy was one which incorporated a variety of tactics.
“In practice, each policy option will fit within a multi-component policy strategy, where policies undoubtedly interact. Our dietary salt consumption is, after all, a product of our personal agency and the structure of our environment.
“For example, ‘nudge’ campaigns are likely to be enhanced by more supportive environments, [such as] concurrent action on price, reformulation and labelling.”
Experts have suggested that the UK's successful reformulation programme - which has since been disrupted by the Tory government's Responsibility Deal - bridged the gap between voluntary and mandatory.
It brought together all major players in the industry on a voluntary basis but allowed each company to make sure the others were sticking to agreed targets - creating a sort of obligatory compliance among competitors.
Source: PLOS One
Published online: 1 July 2015, DOI: 10.1371/journal.pone.0127927
“The Health Equity and Effectiveness of Policy Options to Reduce Dietary Salt Intake in England: Policy Forecast“
Authors: D. Gillespie, K. Allen, M. Guzman-Castillo,