Search

The aim of this eighth Science of Salt outcomes review is to identify, summarize, and critically appraise studies on dietary sodium and health outcomes published between November 1, 2018, and August 31, 2019, to extend this series published in the Journal since 2016. The standardized Science of Salt search strategy was conducted. Studies were screened based on a priori defined criteria to identify publications eligible for detailed critical appraisal. The search strategy resulted in 2621 citations with 27 studies on dietary sodium and health outcomes identified. Two studies met the criteria for detailed critical appraisal and commentary. We report more evidence that high sodium intake has detrimental health effects. A post hoc analysis of the Dietary Approaches to Stop Hypertension (DASH) sodium trial showed that lightheadedness occurred at a greater frequency with a high sodium DASH diet compared to a low sodium DASH diet. In addition, evidence from a post‐trial analysis of the Trials of Hypertension (TOHP) I and II cohorts showed that estimates of sodium intake from methods based on spot urine samples are inaccurate and this method alters the linearity of the sodium‐mortality association. Compared to measurement of 24‐hour sodium excretion using three to seven 24‐hour urine collections, estimation of average 24‐hour sodium excretion with the Kawasaki equation appeared to change the mortality association from linear to J‐shaped. Only two high‐quality studies were identified during the review period, both were secondary analyses of previously conducted trials, highlighting the lack of new methodologically sound studies examining sodium and health outcomes.

This systematic literature review and meta‐analysis examined whether 24‐hour diet recall is a valid way to measure mean population sodium intake compared with the gold standard 24‐hour urinary assessment. The authors searched electronic databases MEDLINE, Embase, and Scopus using pre‐defined terms. Studies were eligible for inclusion if they assessed adult humans in free‐living settings, and if they included group means for 24‐hour diet recall and 24‐hour urinary collection of sodium intake in the same participants. Studies that included populations with an active disease state that might interfere with normal sodium metabolism were excluded. Results of 28 studies are included in the meta‐analysis. Overall, 24‐hour diet recall underestimated population mean sodium intake by an average of 607 mg per day compared to the 24‐hour urine collection. The difference between measures from 24‐hour urine and 24‐hour diet recall was smaller in studies conducted in high‐income countries, in studies where multiple‐pass methods of 24‐hour diet recall were reported and where urine was validated for completeness. Higher quality studies also reported smaller differences between measures than lower quality studies. Monitoring of population sodium intake with 24‐hour urinary excretion remains the most accurate method of assessment. Twenty‐four‐hour diet recall tends to underestimate intake, although high‐quality 24‐hour diet recall improves accuracy, and may be used if 24‐hour urine is not feasible.

The Global Burden of Disease (GBD) 2010 study estimated national salt intake for 187 countries based on data available up to 2010. The purpose of this review was to identify studies that have measured salt intake in a nationally representative population using the 24‐hour urine collection method since 2010, with a view to updating evidence on population salt intake globally. Studies published from January 2011 to September 2018 were searched for from MEDLINE, Scopus, and Embase databases using relevant terms. Studies that provided nationally representative estimates of salt intake among the healthy adult population based on the 24‐hour urine collection were included. Measured salt intake was extracted and compared with the GBD estimates. Of the 115 identified studies assessed for eligibility, 13 studies were included: Four studies were from Europe, and one each from the United States, Canada, Benin, India, Samoa, Fiji, Barbados, Australia, and New Zealand. Mean daily salt intake ranged from 6.75 g/d in Barbados to 10.66 g/d in Portugal. Measured mean population salt intake in Italy, England, Canada, and Barbados was lower, and in Fiji, Samoa, and Benin was higher, in recent surveys compared to the GBD 2010 estimates. Despite global targets to reduce population salt intake, only 13 countries have published nationally representative salt intake data since the GBD 2010 study. In all countries, salt intake levels remain higher than the World Health Organization's recommendation, highlighting the need for additional global efforts to lower salt intake and monitor salt reduction strategies.

This systematic literature review aimed to investigate whether 24 hour diet recall and diet records are reliable and valid ways to measure usual dietary sodium intake compared with 24 hour urinary assessment. We searched electronic databases Medline, Embase, Cinahl, Lilacs, Google Scholar and the Cochrane Library using pre‐defined terms Studies were eligible for inclusion if they assessed adult humans in free‐living settings, and if they included dietary assessment and 24 hours urinary collection for assessment of sodium intake in the same participants. Studies that included populations with an active disease state that might interfere with normal sodium metabolism were excluded. Results of 20 studies using 24 hour diet recall recall (including 14 validation studies) and 10 studies using food records (including six validation studies) are included in this review. Correlations between estimates from dietary assessment and urinary excretion ranged from 0.16 to 0.72 for 24 hour diet recall, and 0.11 to 0.49 for food diaries. Bland‐Altman analysis in two studies of 24 hour diet recall showed poor agreement with 24 hours urinary sodium excretion. These results show that 24 hour diet recall and diet records inaccurately measure dietary sodium intake in individuals compared with the gold standard 24 hours urinary excretion. Validation studies of dietary assessment methods should include multiple days of assessment and 24 hours urine collection, use relevant food composition databases and Bland‐Altman methods of analysis.

The aim of the current review was to examine the scope of studies published in the Science of Salt Weekly that contained a measure of self‐reported knowledge, attitudes, and behavior (KAB) concerning salt. Specific objectives were to examine how KAB measures are used to evaluate salt reduction intervention studies, the questionnaires used, and whether any gender differences exist in self‐reported KAB. Studies were reviewed from the commencement of Science of Salt Weekly, June 2013 to the end of August 2017. Seventy‐five studies had relevant measures of KAB and were included in this review, 13 of these were salt‐reduction intervention‐evaluation studies, with the remainder (62) being descriptive KAB studies. The KAB questionnaires used were specific to the populations studied, without evidence of a best practice measure. 40% of studies used KAB alone as the primary outcome measure; the remaining studies used more quantitative measures of salt intake such as 24‐hour urine. Only half of the descriptive studies showed KAB outcomes disaggregated by gender, and of those, 73% showed women had more favorable KAB related to salt. None of the salt intervention‐evaluation studies showed disaggregated KAB data. Therefore, it is likely important that evaluation studies disaggregate, and are appropriately powered to disaggregate all outcomes by gender to address potential disparities.

Food frequency questionnaires (FFQs) are often used to assess dietary sodium intake, although 24‐hour urinary excretion is the most accurate measure of intake. The authors conducted a systematic review to investigate whether FFQs are a reliable and valid way of measuring usual dietary sodium intake. Results from 18 studies are described in this review, including 16 validation studies. The methods of study design and analysis varied widely with respect to FFQ instrument, number of 24‐hour urine collections collected per participant, methods used to assess completeness of urine collections, and statistical analysis. Overall, there was poor agreement between estimates from FFQ and 24‐hour urine. The authors suggest a framework for validation and reporting based on a consensus statement (2004), and recommend that all FFQs used to estimate dietary sodium intake undergo validation against multiple 24‐hour urine collections.

This periodic review aims to identify, summarize, and appraise studies relating to the implementation of salt reduction strategies that were published between September 2016 and February 2017. A total of 41 studies were included as relevant to the design, assessment, and implementation of salt reduction strategies, and a detailed appraisal was conducted on the seven studies that evaluated the impact of salt reduction strategies. Of these, three were national studies or included large populations and four were conducted in communities with small participant sample sizes. Each study used a different strategy for reducing salt intake varying from category‐specific sodium targets for packaged food to use of a low‐sodium salt substitute to behavior change interventions. Four studies found statistically significant decreases in dietary salt intake and one study showed statistically significant decreases in mean sodium density of packaged food products. Four of the seven studies used either spot or 24‐hour urine samples to measure dietary salt intake and five were conducted in East or Southeast Asia—two of which were in low‐ and middle‐income countries. Study quality varied among the seven studies and all except one had one or more risks related to bias.

The objective of this periodic review was to identify, summarize, and appraise studies relating to the implementation of salt reduction strategies that were retrieved between November 2015 and February 2016. From the established MEDLINE search, 56 studies were identified as relevant to the implementation of salt reduction initiatives. Detailed appraisal was performed on seven studies that evaluated the impact of salt reduction interventions. While study quality varied, all had one or more risks related to bias. There was consistent evidence, from three studies, demonstrating that setting‐based structural interventions to improve the nutritional composition of foods were effective in reducing salt but mixed evidence in relation to the effectiveness of behavioral interventions. The development of an evaluation guidance framework that supports scientific rigor and external validity would aid future design and interpretation of studies evaluating salt reduction interventions, particularly for low‐resource countries.

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.