Conclusions drawn from a 70-study review found that multi-component strategies, involving both individual and population-wide interventions, achieve salt intake reductions most notably 4 grams per day (g/day) in Finland and Japan, 3g /day in Turkey and 1.3 g/day recently in the UK.
“There are clear implications for public health,” the review concludes. “The biggest population-wide reductions in salt consumption involved “upstream” population-wide policies (regulation, mandatory reformulation, and food labelling).
”Downstream” individually-based interventions appear relatively weak (e.g. dietary counselling to individuals and school children, and media campaigns in isolation).”
The team, made up of researchers from the Universities of Liverpool and Warwick, spoke of an “effectiveness hierarchy,” in which health policies that target populations over high-risk individuals are more effective.
Emerging evidence suggests that a similar hierarchy might exist for salt reduction strategies, whereby upstream interventions apparently achieve bigger reductions in salt intake.
The review noted the downstream interventions adopted in tobacco control and alcohol policies as an example of less successful approaches.
The UK Responsibility Deal
The UK and other high-income countries consume over 70% of dietary salt through processed foods such as bread, breakfast cereals, processed meats, snack foods, soups and sauces.
This food environment contributes to excessive salt intake among adults, on average 10 g/day or more. The World Health Organisation (WHO) recommends a maximum adult salt intake of 5 g/day.
Finland and, more recently, the UK have put in place policies designed to reduce salt intake.
In the UK, awareness campaigns, agreed target settings, voluntary industry reformulation and population monitoring of salt consumption led to a 1.4 g/day reduction in population salt intake between 2001 and 2011.
However, the introduction of the Responsibility Deal in 2010, which shifted emphasis to downstream interventions, coupled with ineffective voluntary agreements and, controversially, the direct involvement of the industry in policy decisions, reversed this downward trend.
After screening 2,526 candidate papers, 70 were included in the systematic review (49 empirical studies and 21 modelling studies).
Two researchers searched six electronic databases (CDSR, CRD, MEDLINE, SCI, SCOPUS and the Campbell Library).
Retrieved papers were independently screened, appraised and graded for quality.
Along with the salt reductions of 4 g/day in Finland and Japan, 3 g/day in Turkey and 1.3 g/day in the UK, the team found mandatory reformulation alone could achieve a reduction of approximately 1.45 g/day.
This was followed by voluntary reformulation (-0.8 g/day), school interventions (-0.7 g/day), short-term dietary advice (-0.6 g/day) and nutrition labelling (-0.4 g/day).
Tax and community based counselling could, each typically reduce salt intake by 0.3 g/day, whilst even smaller population benefits were derived from health education media campaigns (-0.1 g/day).
Worksite interventions achieved an increase in intake (+0.5 g/day), however, with a very wide range.
Long-term dietary advice could achieve a -2 g/day reduction under optimal research trial conditions; however, smaller reductions might be expected in certain individuals.
Other dietary changes
“This systematic review of salt reduction interventions suggests that comprehensive strategies could generally achieve the biggest reductions in salt consumption across an entire population,” the team highlighted.
“Multi-component salt reduction strategies involving a series of structural initiatives together with campaigns to increase population awareness have been successful in Japan and Finland.
“In Finland, some credit should also go to other dietary changes e.g. fat quality.”
The results are consistent with growing evidence that suggest population-wide prevention policies can often be powerful, rapid, equitable and cost-saving.
Several modelling studies, which also investigated the cost-effectiveness of the salt interventions outlined in this study, found mandatory and voluntary reformulation appeared far more cost-effective than labelling or dietary advice targeting individuals.
The team also highlighted that more deprived groups are likely to consume foods high in salt, (and sugar and fat).
These inequalities persist in Britain and Italy, the team stated, also noting that downstream interventions typically widen inequalities whereas upstream interventions may reduce inequalities.
Source: PLOS One
Published online ahead of print: doi.org/10.1371/journal. pone.0177535
“Systematic review of dietary salt reduction policies: Evidence for an effectiveness hierarchy?”
Authors: Lirije Hyseni, Alex Elliot-Green, Ffion Lloyd-Williams, Chris Kypridemos, Martin O’Flaherty, Rory McGill, Lois Orton, Helen Bromley, Francesco P. Cappuccio, Simon Capewell