Is reducing dietary sodium controversial? Is it the conduct of studies with flawed research methods that is controversial? A perspective from the World Hypertension League Executive Committee

It is strongly recommended to not conduct, fund, or publish research studies that use spot urine samples with estimating equations to assess individuals' sodium (salt) intake in association with health outcomes: a policy statement of the World Hypertension League, International Society of Hypertension and Resolve to Save Lives

Spot urine samples with estimating equations have been used to assess individuals' sodium (salt) intake in association with health outcomes. There is large random and systematic error in estimating sodium intake using this method and spurious health outcome associations. Substantial controversy has resulted from false claims the method is valid. Hence, the World Hypertension League, International Society of Hypertension and Resolve to Save Lives, supported by 21 other health organizations, have issued this policy statement that strongly recommends that research using spot urine samples with estimating equations to assess individuals' sodium (salt) intake in association with health outcomes should not be conducted, funded or published. Literature reviews on the health impacts of reducing dietary sodium that include studies that have used spot and short duration timed urine samples with estimating equations need to explicitly acknowledge that the method is not recommended to be used and is associated with spurious health outcome associations.

The Sweet and Salty Dietary Face of Hypertension and Cardiovascular Disease in Lebanon

According to the World Health Organization (WHO), an estimated 1.28 billion adults aged 30–79 years worldwide have hypertension; and every year, hypertension takes 7.6 million lives. High intakes of salt and sugar (mainly fructose from added sugars) have been linked to the etiology of hypertension, and this may be particularly true for countries undergoing the nutrition transition, such as Lebanon. Salt-induced hypertension and fructose-induced hypertension are manifested in different mechanisms, including Inflammation, aldosterone-mineralocorticoid receptor pathway, aldosterone independent mineralocorticoid receptor pathway, renin-angiotensin system (RAS), sympathetic nervous system (SNS) activity, and genetic mechanisms. This review describes the evolution of hypertension and cardiovascular diseases (CVDs) in Lebanon and aims to elucidate potential mechanisms where salt and fructose work together to induce hypertension. These mechanisms increase salt absorption, decrease salt excretion, induce endogenous fructose production, activate fructose-insulin-salt interaction, and trigger oxidative stress, thus leading to hypertension. The review also provides an up-to-date appraisal of current intake levels of salt and fructose in Lebanon and their main food contributors. It identifies ongoing salt and sugar intake reduction strategies in Lebanon while acknowledging the country’s limited scope of regulation and legislation. Finally, the review concludes with proposed public health strategies and suggestions for future research, which can reduce the intake levels of salt and fructose levels and contribute to curbing the CVD epidemic in the country.

Estimating the health and economic effects of the voluntary sodium reduction targets in Brazil: microsimulation analysis

BACKGROUND

Excessive sodium consumption is one of the leading dietary risk factors for non-communicable diseases, including cardiovascular disease (CVD), mediated by high blood pressure. Brazil has implemented voluntary sodium reduction targets with food industries since 2011. This study aimed to analyse the potential health and economic impact of these sodium reduction targets in Brazil from 2013 to 2032.

METHODS

We developed a microsimulation of a close-to-reality synthetic population (IMPACTNCD-BR) to evaluate the potential health benefits of setting voluntary upper limits for sodium content as part of the Brazilian government strategy. The model estimates CVD deaths and cases prevented or postponed, and disease treatment costs. Model inputs were informed by the 2013 National Health Survey, the 2008-2009 Household Budget Survey, and high-quality meta-analyses, assuming that all individuals were exposed to the policy proportionally to their sodium intake from processed food. Costs included costs of the National Health System on CVD treatment and informal care costs. The primary outcome measures of the model are cardiovascular disease cases and deaths prevented or postponed over 20 years (2013-2032), stratified by age and sex.

RESULTS

The study found that the application of the Brazilian voluntary sodium targets for packaged foods between 2013 and 2032 could prevent or postpone approximately 110,000 CVD cases (95% uncertainty intervals (UI): 28,000 to 260,000) among men and 70,000 cases among women (95% UI: 16,000 to 170,000), and also prevent or postpone approximately 2600 CVD deaths (95% UI: - 1000 to 11,000), 55% in men. The policy could also produce a net cost saving of approximately US$ 220 million (95% UI: US$ 54 to 520 million) in medical costs to the Brazilian National Health System for the treatment of CHD and stroke and save approximately US$ 71 million (95% UI: US$ 17 to170 million) in informal costs.

CONCLUSION

Brazilian voluntary sodium targets could generate substantial health and economic impacts. The reduction in sodium intake that was likely achieved from the voluntary targets indicates that sodium reduction in Brazil must go further and faster to achieve the national and World Health Organization goals for sodium intake.

Salt Reduction Initiatives in the Eastern Mediterranean Region and Evaluation of Progress towards the 2025 Global Target: A Systematic Review

This study aims at identifying national salt reduction initiatives in countries of the Eastern Mediterranean Region and describing their progress towards the global salt reduction target. A systematic review of published and grey literature was conducted. Key characteristics of strategies were extracted and classified according to a pre-defined framework: salt intake assessments; leadership and strategic approach; implementation strategies; monitoring and evaluation of program impact. Salt intake levels were estimated in 15 out of the 22 countries (68%), while national salt reduction initiatives were identified in 13 (59%). The majority of countries were found to implement multifaceted reduction interventions, characterized by a combination of two or more implementation strategies. The least common implementation strategy was taxation, while the most common was reformulation (100%), followed by consumer education (77%), initiatives in specific settings (54%), and front of pack labelling (46%). Monitoring activities were conducted by few countries (27%), while impact evaluations were lacking. Despite the ongoing salt reduction efforts in several countries of the region, more action is needed to initiate reduction programs in countries that are lagging behind, and to ensure rigorous implementation and evaluations of ongoing programs. Such efforts are vital for the achievement of the targeted 30% reduction in salt intake.

Dietary Sodium 'Controversy'-Issues and Potential Solutions

PURPOSE OF REVIEW

High dietary sodium is estimated to be the leading dietary risk for death attributed to 1.8 million deaths in 2019. There are uniform recommendations to reduce sodium consumption based on evidence that increased dietary sodium is responsible for approximately a third of the prevalence of hypertension, and meta-analyses of randomized controlled trials show that sodium reduction lowers blood pressure, cardiovascular disease, and total mortality. Nevertheless, there is a perception that the beneficial effect of reducing dietary sodium is controversial. We provide experiential evidence relating to some sources of the controversy and propose potential solutions.

RECENT FINDINGS

Inappropriate research methodology, lack of rigor in research, conflicts of interest and commercial bias, questions of professional conduct, and lack of policies to protect public interests are likely to contribute to the controversy about reducing dietary sodium. There is a failure to protect policies to reduce dietary sodium from nonscientific threats. Significant efforts need to be made to ensure the integrity of nutritional research and maintain public trust.

Blood Pressure Effects of Sodium Reduction: Dose-Response Meta-Analysis of Experimental Studies

Supplemental Digital Content is available in the text.

Background:

The relationship between dietary sodium intake and blood pressure (BP) has been tested in clinical trials and nonexperimental human studies, indicating a direct association. The exact shape of the dose–response relationship has been difficult to assess in clinical trials because of the lack of random-effects dose–response statistical models that can include 2-arm comparisons.

Methods:

After performing a comprehensive literature search for experimental studies that investigated the BP effects of changes in dietary sodium intake, we conducted a dose–response meta-analysis using the new 1-stage cubic spline mixed-effects model. We included trials with at least 4 weeks of follow-up; 24-hour urinary sodium excretion measurements; sodium manipulation through dietary change or supplementation, or both; and measurements of systolic and diastolic BP at the beginning and end of treatment.

Results:

We identified 85 eligible trials with sodium intake ranging from 0.4 to 7.6 g/d and follow-up from 4 weeks to 36 months. The trials were conducted in participants with hypertension (n=65), without hypertension (n=11), or a combination (n=9). Overall, the pooled data were compatible with an approximately linear relationship between achieved sodium intake and mean systolic as well as diastolic BP, with no indication of a flattening of the curve at either the lowest or highest levels of sodium exposure. Results were similar for participants with or without hypertension, but the former group showed a steeper decrease in BP after sodium reduction. Intervention duration (≥12 weeks versus 4 to 11 weeks), type of study design (parallel or crossover), use of antihypertensive medication, and participants’ sex had little influence on the BP effects of sodium reduction. Additional analyses based on the BP effect of difference in sodium exposure between study arms at the end of the trial confirmed the results on the basis of achieved sodium intake.

Conclusions:

In this dose–response analysis of sodium reduction in clinical trials, we identified an approximately linear relationship between sodium intake and reduction in both systolic and diastolic BP across the entire range of dietary sodium exposure. Although this occurred independently of baseline BP, the effect of sodium reduction on level of BP was more pronounced in participants with a higher BP level.

Developing and applying a costing tool for hypertension and related cardiovascular disease: Attributable costs to salt/sodium consumption

This paper proposes a costing tool for hypertension and cardiovascular disease by adapting cost-of-illness methodologies to estimate the attributable burden of excessive salt intake on cardiovascular disease. The methodology estimates the changes in blood pressure that result from each gram change in salt intake and links diet to the direct and indirect costs of cardiovascular diseases (CVD), such as coronary heart disease, stroke, hypertensive disease, aortic aneurysm, heart failure, pulmonary embolism, and rheumatic heart, using the relative risks of disease and the prevalence of salt consumption in the population. The methodology includes (a) identifying major diseases and conditions related to excessive salt intake and relevant economic cost data available, (b) quantifying the relationship between the prevalence of excessive salt intake and the associated risk of disease morbidity and mortality using population attributable risks (PAR), (c) using PARs to estimate the share of total costs directly attributed to excessive salt intake, and (d) undertaking a sensitivity analysis of key epidemiological and economic parameters. The costing tool has estimated that, in 2013, US$ 102.0 million (95% uncertainty interval-UI: US$ 96.2-107.8 million) in public hospitalizations could be saved if the average salt intake of Brazilians were reduced to 5 g/d, corresponding to 9.4% (95% UI: 8.9%-9.9%) of the total hospital costs by CVDs. This methodology of cost of illness associated with salt consumption can be adapted to estimate the burden of other dietary risk factors and support prevention and control policies in Brazil and in other countries.

The Science of Salt: A Systematic Review of Quality Clinical Salt Outcome Studies June 2014 to May 2015

Studies identified from an updated systematic review (from June 2014 to May 2015) on the impact of dietary salt intake on clinical and population health are reviewed. Randomized controlled trials, cohort studies, and meta-analyses of these study types on the effect of sodium intake on blood pressure, or any substantive adverse health outcomes were identified from MEDLINE searches and quality indicators were used to select studies that were relevant to clinical and public health. From 6920 studies identified in the literature search, 144 studies were selected for review, of which only three (n=233,680) met inclusion criteria. Between them, the three studies demonstrated a harmful association between excess dietary salt and all-cause mortality, noncardiovascular and cardiovascular disease mortality, and headache. None of the included studies found harm from lowering dietary salt. The findings of this systematic review are consistent with the large body of research supportive of efforts to reduce population salt intake and congruent with our last annual review from June 2013 to May 2014.

Salt Reduction Initiatives around the World - A Systematic Review of Progress towards the Global Target

OBJECTIVE

To quantify progress with the initiation of salt reduction strategies around the world in the context of the global target to reduce population salt intake by 30% by 2025.

METHODS

A systematic review of the published and grey literature was supplemented by questionnaires sent to country program leaders. Core characteristics of strategies were extracted and categorised according to a pre-defined framework.

RESULTS

A total of 75 countries now have a national salt reduction strategy, more than double the number reported in a similar review done in 2010. The majority of programs are multifaceted and include industry engagement to reformulate products (n = 61), establishment of sodium content targets for foods (39), consumer education (71), front-of-pack labelling schemes (31), taxation on high-salt foods (3) and interventions in public institutions (54). Legislative action related to salt reduction such as mandatory targets, front of pack labelling, food procurement policies and taxation have been implemented in 33 countries. 12 countries have reported reductions in population salt intake, 19 reduced salt content in foods and 6 improvements in consumer knowledge, attitudes or behaviours relating to salt.

CONCLUSION

The large and increasing number of countries with salt reduction strategies in place is encouraging although activity remains limited in low- and middle-income regions. The absence of a consistent approach to implementation highlights uncertainty about the elements most important to success. Rigorous evaluation of ongoing programs and initiation of salt reduction programs, particularly in low- and middle- income countries, will be vital to achieving the targeted 30% reduction in salt intake.

The World Hypertension League: where now and where to in salt reduction

High dietary salt is a leading risk for death and disability largely by causing increased blood pressure. Other associated health risks include gastric and renal cell cancers, osteoporosis, renal stones, and increased disease activity in multiple sclerosis, headache, increased body fat and Meniere's disease. The World Hypertension League (WHL) has prioritized advocacy for salt reduction. WHL resources and actions include a non-governmental organization policy statement, dietary salt fact sheet, development of standardized nomenclature, call for quality research, collaboration in a weekly salt science update, development of a process to set recommended dietary salt research standards and regular literature reviews, development of adoptable power point slide sets to support WHL positions and resources, and critic of weak research studies on dietary salt. The WHL plans to continue to work with multiple governmental and non-governmental organizations to promote dietary salt reduction towards the World Health Organization (WHO) recommendations.

Salt and sugar: their effects on blood pressure

Both dietary salt and sugar are related to blood pressure (BP). The evidence for salt is much stronger, and various types of studies have consistently shown that salt is a major cause of raised BP, and a reduction from the current intake of ≈ 9-12 g/day in most countries of the world to the recommended level of 5-6 g/day lowers BP in both hypertensive and normotensive individuals, in men and women, in all age groups and in all ethnic groups. Countries such as Finland and the UK that have successfully reduced salt intake have demonstrated a reduction in population BP and cardiovascular mortality, with major cost savings to the health service. The mechanisms whereby salt raises BP are not fully understood. The traditional concepts focus on the tendency for an increase in extracellular fluid volume. Increasing evidence suggests that small increases in plasma sodium may play an important role. There are several other factors that also increase BP, one of which is added sugars. The current high intake of added sugars increases obesity which, in turn, raises BP. Recent studies also suggest that added sugars, particularly those in soft drinks, may have a direct effect on BP. However, the relationship between soft drink consumption and BP could be, at least partially, mediated by the effect of salt intake on increasing soft drink consumption. Actions to reduce salt and sugar intake across the whole population will have major beneficial effects on health along with major cost savings.