Earlier this week the following paper was published, which investigates the potential impact of proposed salt reduction work in the US. Read on for our summary of the findings.
Pearson-Stuttard J., Kypridemos C., Collins B., Mozaffarian D., Huang Y., Bandosz P. et al. Estimating the health and economic effects of the proposed US Food and Drug Administration voluntary sodium reformulation: Microsimulation cost-effectiveness analysis. PLoS Medicine, 2018
In 2016, the US Food and Drink Administration (FDA) proposed salt reduction guidelines for 155 categories of food that are commonly eaten in the US. The guidelines laid out maximum and average levels of salt (per 100g) allowed in food products in each category in the short term (2 years) and the longer term (10 years)1.
This follows similar work in the UK where the UK Food Standards Agency developed and implemented salt reduction guidelines on 85 categories of food in 2006, which were gradually reset to lower targets in 2009 and 2014. By slowly reducing the amount of salt in food products, the UK population’s salt intake fell from 9.5g to 8.1g between 2003 and 2011, which also lead to a drop in average blood pressure and fewer deaths from cardiovascular diseases, such as strokes and heart attacks2.
Despite the proven success of the UK’s salt reduction strategy, the FDA’s salt reduction guidelines remain in a draft form. The guidelines were not popular with some food companies, who asked the House Appropriations Committee (a committee of the US House of Representatives, responsible for allocating money to federal government departments, agencies, and programs, including the FDA) to advise the FDA to delay implementation of the guidelines. They requested a delay until the Centres for Disease Control and Prevention (CDC) had completed review work on the Dietary Reference Intake (DRI) value for salt (due for completion in 2018)3,4. The House Appropriations Committee also included a provision that salt reduction could not be enacted in schools in their 2018 Agriculture Appropriations Bill, until the CDC work was completed5.
However, in a positive development, earlier this month the FDA Commissioner Scott Gottlieb reinforced the FDA’s commitment to salt reduction, hinting that the FDA would implement the short-term targets by 2019 and stating that salt reduction is essential to ‘meaningful’ nutrition initiatives6.
The researchers aimed to investigate the potential health and economic benefits to the US population if the FDA’s guidance was implemented over a 20-year period (2017-2036).
They used the US IMPACT Food Policy Model to investigate potential outcomes. This model can help predict outcomes of an intervention using data on the current, or baseline, situation, and data related to known effects of an intervention. The model used data from the National Health and Nutrition Examination Survey (NHANES), which assesses the health and nutritional status of adults and children in the United States, on current salt intake in the baseline population. The model also used data from the UK salt reduction strategy to predict the cost of implementing and monitoring the FDA guidance.
The researchers also developed three scenarios to investigate:
- OPTIMAL – 100% compliance to the FDA’s guidance, all products are reformulated
- MODEST – 50% compliance with the maximum 2-year and 10-year targets, and 50% compliance with the average 2-year and 10-year targets
- PESSIMISTIC – all processed food is reformulated to meet the 2-year targets, but no further action is taken following this initial reformulation work.
The researchers compared all three scenarios against the current baseline and aimed to determine the effects of salt reduction on health, focusing on blood pressure, coronary heart disease and strokes. They also aimed to determine the cost effectiveness of the guidelines.
By 2036, the model predicted that without FDA guidance, salt intake in the US would be 7.4g/day. They predicted that salt intake would slowly fall over the 20-year period based on the slow declining trend in salt consumption seen in the US from national health survey data.
The model predicted the following impacts on health:
|Median salt consumption||5.6g/day||6.3g/day||7.0g/day|
|Median systolic blood pressure||114 mm/Hg||114.5 mmHg||115 mm/Hg|
|Heart disease cases prevented/postponed||260,000||120,000||63,000|
|Heart disease deaths prevented/postponed||22,000||11,000||7,400|
|Stroke cases prevented/postponed||180,000||93,000||52,000|
|Stroke deaths prevented/postponed||13,000||7,400||5,600|
|All deaths prevented/postponed||83,000||41,000||22,000|
Adapted from Table 2 of the publication
The table highlights that the optimal scenario has the most benefit for health, preventing or postponing double the heart disease and stroke cases or deaths compared to the modest scenario, and four times as many as the pessimistic scenario. However, the researchers also found that the pessimistic scenario, even with minimal compliance, would still lead to health benefits to the population, thus demonstrating the effectiveness of population salt reduction.
The model also predicted the following economic benefits:
|Healthcare cost savings||$31 billion||$16 billion||$9.7 billion|
|Societal cost savings||$41 billion||$19 billion||$12 billion|
|Net Benefit||$250 billion||$130 billion||$81 billion|
Adapted from Table 4 of the publication
Healthcare cost savings refer to savings for the government and those paying for private healthcare. Societal cost refers to the cost saved by more people in the population being healthier, not requiring care and being able to work due to a reduction of illness. The net benefit takes into account the cost of implementing and monitoring the FDA guidelines, along with costs incurred by the food industry in reformulating their products, and balances this against the improvement in health and reduced health costs and care. The net benefit calculation values one year of good health, or a ‘Quality Adjusted Life Year (QALY)’ at $100,000.
Again, even the pessimistic scenario resulted in reduced costs, and health benefits, for the US population. However, the net benefit of the optimal scenario is three times the pessimistic scenario.
This is a great modelling study, which demonstrates the huge potential benefit of salt reduction to our health, and clearly underlines the necessity of proper monitoring and evaluation of salt reduction strategies to ensure their success.
There are some limitations to this study. Modelling studies are useful for public health policy planning, but are only ever a simulation and therefore the findings are not set in stone. The model appears robust, but it can only take into account factors it has been told about and cannot respond to other arising factors.
Additionally, the scenarios used by the researchers are not very reflective of what will be possible in practice. We refer specifically to the OPTIMAL scenario – 100% compliance, leading to reformulation of all processed foods by all manufacturers. The FDA guidance are voluntary and so food companies can choose to adhere to the targets. Under a robust voluntary salt reduction programme, with public monitoring, companies can be encouraged to adhere to targets through negative press of their non-compliance. However, even in the most successful voluntary salt reduction strategy to date – the UK’s salt reduction strategy – not all manufacturers participated and reformulated their products. 100% compliance can only be ensured by making the targets mandatory.
Conversely, the study was probably quite conservative in its predicted impact on health, as it did not take in to account the effect of salt intake on other health conditions, such as stomach cancer, osteoporosis and kidney disease. Furthermore, as food from the US is exported, notably to Canada and Mexico, other populations will benefit from an improved food supply and the example set by the US.
This study serves as a useful resource for countries currently developing salt reduction strategies, and hopefully can be a tool for reinvigoration of salt reduction work worldwide.
- He FJ et al. Salt reduction in England from 2003 to 2011: its relationship to blood pressure, stroke and ischaemic heart disease mortality BMJ Open;4:e004549 (2014)