Dietary Sodium 'Controversy'-Issues and Potential Solutions

Formula-led methods using first morning fasting spot urine to assess usual salt intake: a secondary analysis of PURE study data

OBJECTIVES

Observational studies that assess the relationship between salt intake and long-term outcomes require a valid estimate of usual salt intake. The gold-standard measure in individuals is sodium excretion in multiple nonconsecutive 24-h urines. Multiple studies have demonstrated that random spot urine samples are not valid for estimating usual salt intake; however, some researchers believe that fasting morning spot urine samples produce a better measure of usual salt intake than random spot samples.

METHODS

We have used publicly available data from a PURE China validation study to compare estimates of usual salt intake from morning spot urine samples and four published formulae with mean of two 24-h urine samples (reference). We estimated the mean and 95% confidence interval of absolute and relative error for each formula-led method and the degree to which estimates were able to be classified into the correct quartile of intake. Bland-Altman plots were used to test the level of agreement.

RESULTS

The results show that compared with the reference method, all formulae-led estimates from spot urine collections have high error rates: both random and systematic. This is demonstrated for individual estimates, as well as by quartiles of reference salt intake. This study conclusively demonstrates the unsuitability of morning spot urine formula-led estimates of usual salt intake.

CONCLUSION

Our findings support international recommendations to not conduct, fund, or publish research studies that use spot urine samples with estimating equations to assess individuals' salt intake in association with health outcomes.

Misinformation surrounding sodium reduction for blood pressure: content analysis of Japanese posts on X

This content analysis aimed to assess misinformation themes regarding sodium reduction and blood pressure on X with the goal of providing strategies to address and debunk such misinformation. A total of 531 posts were manually coded into sodium-related misinformation themes, with inclusion criteria for posts asserting no association between sodium reduction and hypertension or claiming consuming sodium is beneficial for health. Numbers and post frequencies per misinformation theme were calculated. Post characteristics, including information sources, advertisements and narratives, were coded, and a correlation analysis was conducted to assess their association with each misinformation theme. Fourteen sodium-related misinformation themes were identified and consistently disseminated on X. The predominant theme, 'Natural Salt', accounted for 37.7% (n = 200), reaching 1.6 million followers, followed by 'Reducing salt could be bad for my health' theme, comprising 28.6% (n = 152) and reaching 1.5 million followers. There was a statistical correlation between the natural salt misinformation theme and advertisements. Many of the most frequent misinformation themes identified in this study have not been systematically debunked by organizations such as the World Health Organization and the American Heart Association. This study underscores the importance of continuous monitoring and analysis of sodium-related misinformation on social media platforms and their underlying commercial interests. Such monitoring has the potential to identify prevalent misinformation themes that may pose harm to the public and to inform public health organizations, enabling them to proactively address potential issues through debunking.

Population-level salt intake in the WHO European Region in 2022: a systematic review

OBJECTIVE

The WHO recommends that adults consume less than 5 g of salt per day to reduce the risk of CVD. This study aims to examine the average population daily salt intake in the fifty-three Member States of the WHO European Region.

DESIGN

A systematic review was conducted to examine the most up-to-date salt intake data for adults published between 2000 and 2022. Data were obtained from peer-reviewed and grey literature, WHO surveys and studies, as well as from national and global experts.

SETTING

The fifty-three Member States of the WHO European Region.

PARTICIPANTS

People aged 12 years or more.

RESULTS

We identified fifty studies published between 2010 and 2021. Most countries in the WHO European Region (n 52, 98 %) reported salt intake above WHO recommended maximum levels. In almost all countries (n 52, 98 %), men consume more salt than women, ranging between 5·39 and 18·51 g for men and 4·27 and 16·14 g for women. Generally, Western and Northern European countries have the lowest average salt intake, whilst Eastern European and Central Asian countries have the highest average. Forty-two percentage of the fifty-three countries (n 22) measured salt intake using 24 h urinary collection, considered the gold standard method.

CONCLUSIONS

This study found that salt intakes in the WHO European Region are significantly above WHO recommended levels. Most Member States of the Region have conducted some form of population salt intake. However, methodologies to estimate salt intake are highly disparate and underestimations are very likely.

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.

Comment on Hogas et al. Salt, Not Always a Cardiovascular Enemy? A Mini-Review and Modern Perspective. Medicina 2022, 58, 1175

Hogas et al. recently published their perspective on dietary salt in a mini review [...].

The World Hypertension League Science of Salt: a regularly updated systematic review of salt and health outcomes studies (Sept 2019 to Dec 2020)

The World Hypertension League Science of Salt health outcomes review series highlights high-quality publications relating to salt intake and health outcomes. This review uses a standardised method, outlined in previous reviews and based on methods developed by WHO, to identify and critically appraise published articles on dietary salt intake and health outcomes. We identified 41 articles published between September 2019 to December 2020. Amongst these, two studies met the pre-specified methodological quality criteria for critical appraisal. They were prospective cohort studies and examined physical performance and composite renal outcomes as health outcomes. Both found an association between increased/higher sodium intake and poorer health outcomes. Few studies meet criteria for high-quality methods. This review adds further evidence that dietary salt reduction has health benefits and strengthens evidence relating to health outcomes other than blood pressure and cardiovascular disease. We observe that most studies on dietary sodium do not have adequate methodology to reliably assess sodium intake and its association with health outcomes.

Camel (Camelus spp.) Urine Bioactivity and Metabolome: A Systematic Review of Knowledge Gaps, Advances, and Directions for Future Research

Up to the present day, studies on the therapeutic properties of camel (Camelus spp.) urine and the detailed characterization of its metabolomic profile are scarce and often unrelated. Information on inter individual variability is noticeably limited, and there is a wide divergence across studies regarding the methods for sample storage, pre-processing, and extract derivatization for metabolomic analysis. Additionally, medium osmolarity is not experimentally adjusted prior to bioactivity assays. In this scenario, the methodological standardization and interdisciplinary approach of such processes will strengthen the interpretation, repeatability, and replicability of the empirical results on the compounds with bioactive properties present in camel urine. Furthermore, sample enlargement would also permit the evaluation of camel urine's intra- and interindividual variability in terms of chemical composition, bioactive effects, and efficacy, while it may also permit researchers to discriminate potential animal-intrinsic and extrinsic conditioning factors. Altogether, the results would help to evaluate the role of camel urine as a natural source for the identification and extraction of specific novel bioactive substances that may deserve isolated chemical and pharmacognostic investigations through preclinical tests to determine their biological activity and the suitability of their safety profile for their potential inclusion in therapeutic formulas for improving human and animal health.

Sodium and Health: Old Myths and a Controversy Based on Denial

PURPOSE OF REVIEW

The scientific consensus on which global health organizations base public health policies is that high sodium intake increases blood pressure (BP) in a linear fashion contributing to cardiovascular disease (CVD). A moderate reduction in sodium intake to 2000 mg per day helps ensure that BP remains at a healthy level to reduce the burden of CVD.

RECENT FINDINGS

Yet, since as long ago as 1988, and more recently in eight articles published in the European Heart Journal in 2020 and 2021, some researchers have propagated a myth that reducing sodium does not consistently reduce CVD but rather that lower sodium might increase the risk of CVD. These claims are not well-founded and support some food and beverage industry's vested interests in the use of excessive amounts of salt to preserve food, enhance taste, and increase thirst. Nevertheless, some researchers, often with funding from the food industry, continue to publish such claims without addressing the numerous objections. This article analyzes the eight articles as a case study, summarizes misleading claims, their objections, and it offers possible reasons for such claims. Our study calls upon journal editors to ensure that unfounded claims about sodium intake be rigorously challenged by independent reviewers before publication; to avoid editorial writers who have been co-authors with the subject paper's authors; to require statements of conflict of interest; and to ensure that their pages are used only by those who seek to advance knowledge by engaging in the scientific method and its collegial pursuit. The public interest in the prevention and treatment of disease requires no less.

Mechanism-based strategies to prevent salt sensitivity and salt-induced hypertension

High-salt diets are a major cause of hypertension and cardiovascular (CV) disease. Many governments are interested in using food salt reduction programs to reduce the risk for salt-induced increases in blood pressure and CV events. It is assumed that reducing the salt concentration of processed foods will substantially reduce mean salt intake in the general population. However, contrary to expectations, reducing the sodium density of nearly all foods consumed in England by 21% had little or no effect on salt intake in the general population. This may be due to the fact that in England, as in other countries including the U.S.A., mean salt intake is already close to the lower normal physiologic limit for mean salt intake of free-living populations. Thus, mechanism-based strategies for preventing salt-induced increases in blood pressure that do not solely depend on reducing salt intake merit attention. It is now recognized that the initiation of salt-induced increases in blood pressure often involves a combination of normal increases in sodium balance, blood volume and cardiac output together with abnormal vascular resistance responses to increased salt intake. Therefore, preventing either the normal increases in sodium balance and cardiac output, or the abnormal vascular resistance responses to salt, can prevent salt-induced increases in blood pressure. Suboptimal nutrient intake is a common cause of the hemodynamic disturbances mediating salt-induced hypertension. Accordingly, efforts to identify and correct the nutrient deficiencies that promote salt sensitivity hold promise for decreasing population risk of salt-induced hypertension without requiring reductions in salt intake.