Abstract
Background: Poor sodium and potassium balance (i.e., high sodium and low potassium) intakes is associated with elevated blood pressure, a key predictor of stroke and other non-communicable diseases. Because of this, improving dietary sodium and potassium intakes is of global public health concern. On average, adults consume excess sodium and insufficient potassium compared with recommended levels. Given the increasing popularity of food provision services, more studies have examined whether providing free healthy foods can improve health outcomes. However, few studies have investigated the unintended impact of food provision interventions on sodium and potassium intakes. Additionally, no studies have examined the long-term effects on sodium and potassium intakes over an extended period following the conclusion of the intervention.
Objective: This study aimed to assess changes in sodium and potassium intakes as a result of receiving healthy grocery interventions, and whether any changes in intakes were maintained 3 and 12 months after grocery provision ended.
Methods: The Healthy Heart Study was a randomised three-arm parallel trial designed to investigate the effects of free healthy grocery delivery, in addition to usual care, on cardiometabolic risk factors in adults recovering from an acute coronary event. Participants were randomly assigned to one of three groups: a control group, an intervention group receiving foods rich in unsaturated fats (Healthy Fats), and an intervention group receiving foods rich in dietary fibre (High Fibre). These interventions were not specifically designed to impact sodium and potassium intakes, and therefore this thesis investigates whether these interventions had an unintentional impact on sodium and potassium intakes. Participants in the intervention groups received weekly deliveries of healthy groceries for 12 weeks. Food diaries were completed by all participants at baseline, immediately post-intervention, and at 3-months and 12-months follow-up. Dietary data were entered into FoodWorks 10 and analysed by study group and time point to assess mean sodium and potassium intakes. Differences in sodium and potassium intakes between intervention arms were analysed using generalised linear models (GLMs).
Result: A total of 297 participants were included in this analysis, 32% of whom were female. The study population primarily comprised middle-aged and older adults (mean age 63 years; SD: 10), most of whom were classified as overweight or obese (mean BMI: 30; SD: 5). At baseline, the mean (SD) sodium and potassium intakes across all three groups were 2,348 (830) mg/day and 3,296 (1,018) mg/day, respectively. The High Fibre grocery provision led to a significant increase in potassium intake of 279 mg/day (95% CI: 0, 558) at the end of the intervention, and a reduction in sodium intake of -257 mg/day (95% CI: -512, -1) at the three-month follow-up, when compared with the control group. The Healthy Fats grocery provision did not result in any significant changes in participants’ sodium or potassium intakes.
Conclusion: The food provision intervention, whether provided to the Healthy Fats group or the High Fibre group, did not have a negative impact on sodium or potassium intake. Additionally, the groceries provided to the High Fibre group inadvertently improved potassium intake at the end of the intervention and sodium intake three months after the intervention, indicating that the intervention led to a long-term dietary behaviour change. Therefore, food provision interventions focused on unsaturated fats or dietary fibre do not pose a risk to sodium or potassium intake and, with appropriate consideration of the potassium and sodium content in the provided foods, can temporarily improve potassium intake and support a long-term dietary behaviour change to reduce sodium intake. Although a food provision intervention may not lead to a meaningful long-term increase in potassium intake, it can still serve as an important strategy alongside other sodium reduction initiatives.