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Table 3 Input parameters relating to the four new intervention effects

From: The health gains and cost savings of dietary salt reduction interventions, with equity and age distributional aspects

Intervention Sources and extra details Key values and uncertainty (average adult)a
Salt substitution at 59 %: In all processed food the NaCl is legally required to be largely substituted with other salts at the level of 59 % (mix of potassium and magnesium salts). This 59 % substitution level was that used in a randomised trial in the Netherlands [27]. This trial reported that all the foods were rated equally by both groups for appearance and palatability-except that the bread and table salt were considered “less salty” by those in the intervention group. It was assumed that the intervention would apply to processed foods (72 % of sodium intake in NZ) and table salt (15 % of intake), but not to milk, seafood, fruit, vegetables and fresh meat (13 % of intake) [66]. Of note, is that another study found that consumption of bread was not affected at 52 % reduction in sodium and up to 67 % when KCl and yeast extract was used for flavour compensation [46]. We assumed a phased-in implementation over a five year period (i.e., five equal steps beginning in the baseline year of 2011). Reduction of 51.5 % in daily sodium intake from the reduced intake of processed foods and table salt (or 1824 mg [79.3 mmol] sodium per day for an average adult). For uncertainty we used +/- 10 % of the point estimate (normal distribution).
Salt substitution at 25 %: As per the intervention above but at a lower level. This substitution level is as per the majority of the salt substitution studies in the meta-analysis by Peng et al [16]. The same assumptions about the phase-in period and application to just processed foods and to table salt (as per the intervention directly above) applied. Reduction of 21.8 % in daily sodium intake from the reduced intake of processed foods and table salt (or 773 mg [33.6 mmol] sodium per day for an average adult). For uncertainty we used +/- 10 % of the point estimate (normal distribution).
Tight limits on sodium in bread: A legal requirement for commercial bread to have a sodium level that is ≤280 mg/100 g. This is the level used in Finnish law for the labelling of low salt bread (i.e., 0.7 % salt) [28]. This level is equivalent to 0.28 % sodium which is equivalent to 0.28 g (or 280 mg) sodium per 100 g. For the baseline year we used the mean value of 439 mg/100 g for NZ bread [29]. We also assumed that to ensure ready compliance with the law, the manufacturers aim for an average level in bread that is slightly lower at 270 mg per 100 g. So this would shift the contribution of dietary sodium from bread from 20.6 % [66] to 12.7 % (270/439 x 20.6), i.e., a 7.9 % absolute reduction. That is a reduction of 280 mg/day (out of the baseline consumption of 3544 mg/day [60]). Of note is that this level is still higher than some breads currently on the NZ market e.g., 186 mg/100 g for one multigrain bread [30]. We assumed a phased-in implementation over a five year period (i.e., five equal steps beginning in the baseline year of 2011). Reduction of 7.9 % (or 280 mg [12.2 mmol] sodium per day for an average adult). For uncertainty we used +/- 10 % of the point estimate (normal distribution).
Modest limits on sodium in bread: As per the intervention above but for a less stringent limit of ≤400 mg/100 g (i.e., as per a target value for Australia [31]) As per the row above except that we assumed that to ensure ready compliance with the law, the manufacturers aimed for the 390 mg per 100 g level. So this would shift the dietary contribution of sodium from bread from 20.6 to 18.3 % (390/439 × 20.6), i.e., a 2.3 % absolute reduction. That is a reduction of 81.5 mg/day (out of the baseline consumption of 3544 mg/day). We assumed full implementation in the baseline year. Reduction of 2.3 % (or 81.5 mg [3.5 mmol] sodium per day for an average adult). For uncertainty we used +/- 10 % of the point estimate (normal distribution).
  1. aValues given for the average adult. In the modelling we adjusted these values for men and women by ratios of 4013/3544 and 3115/3544 respectively, given the variation in sodium intakes (in mg) according to national nutrition survey data [60]