Reducing salt intake in Danish families: Effectiveness of salt reduction strategies on sodium and potassium intake, dietary intake and taste sensitivity

Background: High salt consumption is associated with high blood pressure, a main risk factor for morbidity and mortality. Intake of salt greatly exceeds the recommended level of 5-6g/day in most countries worldwide, and in Denmark, the average salt consumption is 9.5g/day in adults. Reducing population salt intake has been identified as one of the most cost effective approaches to prevent and/or reduce the prevalence of high blood pressure (BP) and cardiovascular diseases (CVD), but real-life evidence on effective strategies to reduce population salt intake are limited.

Objective: The overall aim of this thesis was to estimate the effect of providing salt reduced bread with or without dietary counselling on the intake of sodium, potassium and the sodium to potassium ratio in Danish families. Additionally, we assessed if the intervention had an impact on other dietary intake including energy, macronutrients and selected food groups, as well as salt taste sensitivity, and liking of bread with varying salt content.

Design and methods: The study was a four-month, single blinded, cluster randomized controlled trial with a parallel design. Participants were recruited as families consisting of at least one child (3-17y) and one adult (18-65y). Families were randomly assigned to one of three groups, receiving either; salt reduced bread (Intervention A), salt reduced bread with dietary counselling (Intervention B) or bread with a regular salt content (Control).

At baseline and after four months, participant collected 24-h urine samples (children gave one urine sample and adults gave three), and recorded their dietary intake for seven days in a web-based dietary assessment tool. Salt taste sensitivity was measured by salt taste detection threshold (DT) and recognition threshold (RT) according to ISO3972, and liking for bread with a salt content of 0.4g/100g, 0.8g/100g and 1.2g/100g, respectively, was measured using a 7-point hedonic scale.

Results: Eighty-nine families (n=309) were enrolled in the study. The results on salt (sodium) and potassium differed depending on the method used to measure the intake, i.e. 24-h urine collections or dietary records. The following results are based on the measures from the sevenday dietary records in children, to account for the day-to-day variation in intake, and the repeated 24-h urine collections in adults (Golden Standard).

Intervention A resulted in a lower salt intake of 0.8g/day (-1.5, -0.0) and a lower sodium to potassium ratio of 16% (-26, -4) in children. In adults, salt intake was lowered by 0.8g/day (-2.0, 0.5) and the sodium to potassium ratio by 10% (-24, 7). Intervention B resulted in a lower salt intake of 0.8g/day (-1.3, 0.0) and a lower sodium to potassium ratio of 14% (-24, -4) in children.

In adults, salt intake was lowered by 1.5g/day (-2.5, -0.5) and the sodium to potassium by 20% (-32, -7). Intervention A did not result in any differences in the estimated energy intake or the macronutrient distribution compared to the control group, whereas Intervention B resulted in an increased energy intake among adults compared to the control group (841kJ, CI 311, 1372), and a lower E% from saturated fat (-1.0%, CI -1.8, -0.1).

With regard to the food groups, the intervention did not result in any differences between groups in the consumption of ‘bread’ and ‘bread fillings’. Intervention A resulted in a lower intake of ‘cheese and cheese products’ (-38%, CI -57, -10). Intervention B resulted in higher intakes of ‘fish and fish products’ in children (222%, CI 16, 793) and higher intakes of ‘fruit’ (53%, CI 8, 117), ‘breakfast cereals’ (187%, CI 13, 624), and ‘poultry and poultry products’ (219%, CI 11, 813) in adults.

These findings remained significant when taking differences in energy intake into account. The intervention did not significantly affect DT or RT, but Intervention B resulted in a significant reduction in DT of 18% (-28, -7) and a trend towards a reduction in RT of -16% (-30, 2) from baseline to follow-up.

Following the intervention, liking for bread with 0.4g salt/100g was significantly higher in Intervention B compared to the control (0.4, CI 0.1, 0.8) and borderline significantly higher in Intervention A compared to the control (0.4, CI -0.0, 0.8). Conclusion: Providing salt reduced bread with and without dietary counselling was effective in lowering salt (sodium) intake and the sodium to potassium ratio in both children and adults, although not reaching statistical significance in adults receiving salt reduced bread only.

Providing dietary counselling in addition to salt reduced bread lowered the salt intake and the sodium to potassium ratio beyond the effect of providing salt reduced bread alone in adults, but due to methodological limitations, it was not possible to evaluate if the same was true for children. The energy intake and the quality of the diet in terms of the macronutrient distribution and intake of food groups was not affected by providing salt reduced bread alone.

Adding dietary counselling resulted in minor improvements in the dietary quality, as the E% from saturated fat was lowered and fruit consumption increased, but it might also have increased energy intake (among adults). The intervention did not affect the amount of bread consumed differently between the groups and there was no evidence of a compensating behavior by consuming more salt rich bread fillings or other high salt food groups.

The two salt reduction interventions did not affect the salt taste sensitivity compared to the control, but Intervention B resulted in an increased salt taste sensitivity from baseline to followup. Consumption of salt reduced bread in comparison to regular salt bread resulted in higher liking for bread with a low salt content of 0.4g/100g.

The findings from this study can provide practical applications for the bread industry for salt reduction and guide authorities in setting target levels for salt content in bread. Moreover, the advices used in the dietary counselling can provide a foundation for future strategies aiming at lowering salt intake through public education.