The Science of Salt: A Regularly Updated Systematic Review of Salt and Health Outcomes (August to November 2015)

Smoking, dietary factors and major age-related eye disorders: an umbrella review of systematic reviews and meta-analyses

BACKGROUND

There is accumulating evidence of the associations between age-related eye diseases (AREDs) and smoking or dietary factors. We aimed to provide an umbrella review of the published literature pertaining to smoking or dietary intake as risk factors for major AREDs including cataract, glaucoma, age-related macular degeneration (AMD) and diabetic retinopathy.

METHODS

We searched for pertinent systematic reviews or meta-analyses in PubMed and Web of Science until 16 April 2022. We reperformed the meta-analysis of each association using random effects models. The heterogeneity and 95% prediction interval were calculated. The presence of small-study effect or excess significance bias was also assessed.

RESULTS

In total, 64 associations from 25 meta-analyses and 41 associations from 10 qualitative systematic reviews were evaluated. There was convincing (class I) evidence for only one association, namely current smoking and cataract. Two factors had highly suggestive (class II) evidence, namely ever smoking associated with cataract and fish consumption associated with AMD. We also found suggestive (class III) evidence for associations between the dietary intake of omega-3 polyunsaturated fatty acid, lutein, zeaxanthin, vitamin C and the risk of cataract.

CONCLUSIONS

Smoking as a risk factor for cataract was the most robust association we identified. We also identified several dietary elements associated with AREDs. Large prospective studies are warranted to further examine the associations discussed in this review.

PROSPERO REGISTRATION NUMBER

CRD42022339082.

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.

Development and application of the sodium index to estimate and assess sodium intake for Korean adults

BACKGROUND/OBJECTIVES

The purpose of this study was to develop a sodium index, which is a tool for estimating and assessing sodium intake easily and quickly, to assist in the prevention of various diseases induced by excess sodium intake in Korean adults.

SUBJECTS/METHODS

The 24-h urine collection and dietary behavior surveys were performed on 640 healthy people in 4 regions of South Korea, and an equation for the estimation of 24-h sodium intake was developed. The validity and reliability of the equation were verified with 200 adults. The sodium index was developed by converting the estimated sodium intake using the equation. Finally, the sodium intake status of 1,600 adults was assessed using the sodium index.

RESULTS

The equation included sex, age, body mass index, eating habit and dietary behaviors related to sodium intake. In validity test of the equation, the mean bias between sodium intake using 24-h urine analysis and using the equation from the Bland-Altman plots was −1.5 mg/day. The sensitivity and specificity of the equation for estimation of sodium intake were 80.5% and 64.4%, respectively. In the reliability test of the equation, there was no significant difference between the first and second sodium intakes calculated using the equations, and Spearman's correlation coefficient between the 2 sodium intakes was 0.98. Sodium intake can be assessed as ‘very moderate’ for 75–100 on the sodium index, ‘moderate’ for 100–150, ‘careful’ for less than 75 or 150–200, and ‘severe’ for 250 or more. When sodium intake was assessed using the sodium index in 1,600 subjects, 54.3% and 24.3% of the subjects were assessed to be in the ‘careful’ and ‘severe’ categories, respectively.

CONCLUSIONS

Using a simple questionnaire, the sodium index can be used to monitor and assess sodium intake status, assisting in nutrition education and counseling in a large population.

Further evidence that methods based on spot urine samples should not be used to examine sodium-disease relationships from the Science of Salt: A regularly updated systematic review of salt and health outcomes (November 2018 to August 2019)

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.

The Science of Salt: A global review on changes in sodium levels in foods

This review aims to summarize and synthesize studies reporting on changes in sodium levels in packaged food products, restaurant foods, and hospital or school meals, as a result of salt reduction interventions. Studies were extracted from those published in the Science of Salt Weekly between June 2013 and February 2018. Twenty-four studies were identified: 17 assessed the changes in packaged foods, four in restaurant foods, two in hospital or school meals, and one in both packaged and restaurant foods. Three types of interventions were evaluated as part of the studies: voluntary reductions (including targets), labeling, and interventions in institutional settings. Decreases in sodium were observed in all studies (n = 8) that included the same packaged foods matched at two time points, and in the studies carried out in hospitals and schools. However, there was little to no change in mean sodium levels in restaurant foods. The pooled analysis of change in sodium levels in packaged foods showed a decrease in sodium in unmatched food products (-36 mg/100 g, 95% CI -51 to -20 mg/100 g) and in five food categories-breakfast cereals, breads, processed meats, crisps and snacks, and soups. Twenty-two of the 24 studies were from high-income countries, limiting the applicability of the findings to lower resource settings.

The International Consortium for Quality Research on Dietary Sodium/Salt (TRUE) position statement on the use of 24-hour, spot, and short duration (<24 hours) timed urine collections to assess dietary sodium intake

The International Consortium for Quality Research on Dietary Sodium/Salt (TRUE) is a coalition of intentional and national health and scientific organizations formed because of concerns low-quality research methods were creating controversy regarding dietary salt reduction. One of the main sources of controversy is believed related to errors in estimating sodium intake with urine studies. The recommendations and positions in this manuscript were generated following a series of systematic reviews and analyses by experts in hypertension, nutrition, statistics, and dietary sodium. To assess the population's current 24-hour dietary sodium ingestion, single complete 24-hour urine samples, collected over a series of days from a representative population sample, were recommended. To accurately estimate usual dietary sodium at the individual level, at least 3 non-consecutive complete 24-hour urine collections obtained over a series of days that reflect the usual short-term variations in dietary pattern were recommended. Multiple 24-hour urine collections over several years were recommended to estimate an individual's usual long-term sodium intake. The role of single spot or short duration timed urine collections in assessing population average sodium intake requires more research. Single or multiple spot or short duration timed urine collections are not recommended for assessing an individual's sodium intake especially in relationship to health outcomes. The recommendations should be applied by scientific review committees, granting agencies, editors and journal reviewers, investigators, policymakers, and those developing and creating dietary sodium recommendations. Low-quality research on dietary sodium/salt should not be funded, conducted, or published.

Paucity of high-quality studies reporting on salt and health outcomes from the science of salt: A regularly updated systematic review of salt and health outcomes (April 2017 to March 2018)

The purpose of this review is to identify, summarize, and critically appraise studies on dietary salt and health outcomes that were published from April 2017 to March 2018. The search strategy was adapted from a previous systematic review on dietary salt and health. Identified studies were screened based on a priori defined criteria to identify publications eligible for detailed critical appraisals. Overall, 6747 citations were identified by the search strategy, and 42 health outcome studies were identified. Three of the 42 studies met the criteria for methodological quality and health outcomes and underwent detailed critical appraisals and commentary. In addition, a systematic review and meta-analysis was critically appraised, although it did not strictly meet our methodological criteria. All four of the studies critically appraised found that sodium reduction improved blood pressure, especially in individuals with hypertension. In addition, sodium reduction reduced albuminuria in patients with stage 1-3 chronic kidney disease. Examination of the time course of blood pressure responses to sodium reduction revealed lowering sodium in the context of an average American diet may not produce maximal blood pressure reductions within a 4-week intervention period. This review provides further evidence of the benefit of sodium reduction for blood pressure lowering and gives insights into the subgroups of the population that may derive the greatest benefit from sodium reduction and the time course required to see benefit. Only three high-quality studies were identified during this 12-month review period, highlighting the critical need for more well-conducted rigorous studies in this area.

Sources of Dietary Sodium in Food and Beverages Consumed by Spanish Schoolchildren between 7 and 11 Years Old by the Degree of Processing and the Nutritional Profile

Excessive salt intake has negative effects on health and persists as a dietary problem in Spanish children. However, the analysis of dietary sodium sources has not been extensively studied. A group of 321 children between 7 and 11 years old from five Spanish regional communities was studied. A three-day dietary record was used to determine the contribution of food and beverages to dietary sodium intake. The food consumed was classified based on the level of processing (NOVA classification) and the nutritional profile. Boys consumed more dietary sodium and sodium from ultra-processed food (UPF) than girls (p < 0.05). The main sources of dietary sodium from discretionary food were meat and meat products (25.1%), some ready-to-eat and pre-cooked dishes (7.4%) and sugars and sweets (6.3%). More than 4/5 of the total dietary sodium consumed came from processed foods (PF) and UPF. Ready-to-eat and pre-cooked dishes (14.4%), meat and meat products (10.6%), and cereals (10.2%) were the most relevant UPF. These results demonstrate that a key point for Spanish children is a reduction in the sodium content in PF and UPF, whether these foods are for basic or discretionary consumption. Furthermore, a decrease in the frequency and the quantity of discretionary food consumption should be encouraged.

The Science of Salt: A regularly updated systematic review of the implementation of salt reduction interventions (September 2016-February 2017)

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.