No change in 24-h sodium intake estimated from spot urine in Norwegian adults from 2006 to 2019: the population-based Trøndelag Health Study (HUNT)

OBJECTIVE

Monitoring time trends in salt consumption is important for evaluating the impact of salt reduction initiatives on public health outcomes. There has so far not been available data to indicate if salt consumption in Norway has changed during the previous decade. We aimed to assess whether average 24-h salt intake estimated from spot urine samples in the adult population of mid-Norway changed from 2006-2008 to 2017-2019 and to describe variations by sex, age and educational level.

DESIGN

Repeated cross-sectional studies.

SETTING

The population-based Trøndelag Health Study (HUNT).

PARTICIPANTS

In each of two consecutive waves (HUNT3: 2006-2008 and HUNT4: 2017-2019), spot urine samples were collected from 500 men and women aged 25-64 years, in addition to 250 men and women aged 70-79 years in HUNT4. Based on spot urine concentrations of Na, K and creatinine and age, sex and BMI, we estimated 24-h Na intake using the International Cooperative Study on Salt and Blood Pressure (INTERSALT) equation for the Northern European region.

RESULTS

Mean (95 % CI) estimated 24-h salt intakes in men were 11·1 (95 % CI 10·8, 11·3) g in HUNT3 and 10·9 (95 % CI 10·6, 11·1) g in HUNT4, P = 0·25. Corresponding values in women were 7·7 (95 % CI 7·5, 7·9) g and 7·7 (95 % CI 7·5, 7·9) g, P = 0·88. Mean estimated salt intake in HUNT4 decreased with increasing age in women, but not in men, and it did not differ significantly across educational level in either sex.

CONCLUSIONS

Estimated 24-h salt intake in adult men and women in mid-Norway did not change from 2006-2008 to 2017-2019.

Associations between estimation of salt intake and salt-restriction spoons and hypertension status in patients with poorly controlled hypertension: a community-based study from Huzhou City, Eastern China

BACKGROUND

As the prevalence of hypertension increases in China, it is advised to use salt-restriction spoons (SRS) as a lifestyle modification. This study aimed to examine the associations between estimated salt consumption, SRS usage, and the hypertension status in individuals with poorly controlled hypertension.

METHODS

Data was collected in Huzhou City, Zhejiang Province, in 2021 using convenience sampling. The analysis involved ordinal logistic regression and restricted cubic splines to assess the relevant factors.

RESULTS

The study found that 73.34% of the 1215 patients had uncontrolled blood pressure (BP). Urinary excretion was assessed through the utilization of the Kawasaki, INTERSALT, and Tanaka formulas. The outcomes of these three methodologies revealed average daily sodium excretion values of 208.70 (65.65), 154.78 (33.91), and 162.61 (40.87) mmol, respectively. The prevalence of utilizing SRS was found to be 37.78% in this study. Despite the acknowledgment among SRS users of the potential hazards associated with excessive salt consumption, there exists a contradictory pattern of attitudes and behaviors concerning salt reduction. Among individuals with different levels of salt intake (quartiles 1-4, Q1 vs Q4), there was a positive association between limiting salt and hypertension status when controlling for other variables (Kawasaki adjusted OR = 0.58, 95% CI = 0.43-0.79; INTERSALT adjusted OR = 0.62, 95% CI = 0.41-0.92; Tanaka adjusted OR = 0.61, 95% CI = 0.45-0.92, p < 0.05). Our research also revealed that using or used SRS was a protective factor for blood BP control (adjusted OR = 0.79, 95% CI = 0.64-0.99, P < 0.05). The restricted cubic spline plots illustrated a monotonic upward relationship between estimated 24-h urinary Na and BP (P-overall association < 0.05; P-non-linear association > 0.05).

CONCLUSIONS

The use of dietary SRS could result in decrease in daily salt intake for BP control in patients with poorly controlled hypertension. To reduce the impact of high BP in China, additional studies are required to create interventions that can enhance the results for patients.

[Analysis of iodine nutritional status of children aged 8-10 years in Zhejiang Province from 2016 to 2021]

Objective: To analyze the iodine nutrition status of children aged 8 to 10 years in Zhejiang Province from 2016 to 2021. Methods: A multi-stage stratified sampling method was used to select non-residential children aged 8 to 10 years from 90 counties in Zhejiang Province. A total of 114 103 children were included in the study from 2016 to 2021. Direct titration method and arsenic-cerium catalytic spectrophotometry were used to detect salt iodine content and urinary iodine level, respectively, to evaluate the iodine nutritional status of children. Ultrasound was used to detect thyroid volume and analyze the current prevalence of goiter in school-age children. Results: The age of 114 103 children was (9.04 ± 0.81) years old, with 50.0% of (57 083) boys. The median of iodine content M (Q1, Q3) in children's household salt was 23.00 (19.80, 25.20) mg/kg, including 17 242 non-iodized salt, 6 173 unqualified iodized salt, and 90 688 qualified iodized salt. The coverage rate of iodized salt was 84.89%, and the coverage rate of qualified iodized salt was 79.48%. The proportion of non-iodized salt increased from 11.85% in 2016 to 16.04% in 2021 (χ2trend=111.427, P<0.001). The median of urinary iodine concentration M (Q1, Q3) in children was 182.50 (121.00, 261.00) μg/L, among which the proportions of iodine deficiency, iodine suitability, iodine over suitability, and iodine excess were 17.25% (19 686 cases), 39.21% (44 745 cases), 26.85% (30 638 cases), and 16.68% (19 034 cases), respectively. The median of urinary iodine concentration in children in inland areas [M (Q1, Q3): 190.90 (128.80, 269.00) μg/L] was significantly higher than that in children in coastal areas [M (Q1, Q3): 173.00 (113.00, 250.30) μg/L] (P<0.001). From 2016 to 2021, a total of 39 134 ultrasound examinations were conducted, and 1 229 cases of thyroid enlargement were detected. The goiter rate was 3.14% (95%CI: 2.97%-3.32%). The incidence of goiter in children in coastal areas [3.45% (95%CI: 3.19%-3.72%), 641/18 604] was higher than that in children in inland areas [2.86% (95%CI: 2.64%-3.10%), 588/20 530] (P=0.001). Conclusion: From 2016 to 2021, the iodine nutrition level of children aged 8-10 years in Zhejiang Province is generally suitable, and the rate of goiter in children meets the limit of iodine deficiency disease elimination standards.

Salt Intake Estimation from Urine Samples in South Asian Population: Scoping Review

The World Health Organization recommended reducing one's salt intake below 5 g/day to prevent disability and death from cardiovascular and other chronic diseases. This review aimed to identify salt estimation at the population level in South Asian countries, namely Afghanistan, Bangladesh, Bhutan, India, Nepal, Pakistan, and Sri Lanka. We searched electronic databases and government websites for the literature and reports published between January 2011 and October 2021 and also consulted key informants for unpublished reports. We included studies that assessed salt intake from urinary sodium excretion, either spot urine or a 24 h urine sample, on a minimum of 100 samples in South Asian countries. We included 12 studies meeting the criteria after screening 2043 studies, out of which five followed nationally representative methods. This review revealed that salt intake in South Asian countries ranges from 6.7-13.3 g/day. The reported lowest level of salt intake was in Bangladesh and India, and the highest one was in Nepal. The estimated salt intake reported in the nationally representative studies were ranging from 8 g/day (in India) to 12.1 g/day (in Afghanistan). Salt consumption in men (8.9-12.5 g/day) was reported higher than in women (7.1-12.5 g/day). Despite the global target of population salt intake reduction, people in South Asian countries consume a much higher amount of salt than the WHO-recommended level.

Survey of iodized salt coverage in areas with different water iodine concentrations and the iodine status of local women

PURPOSE

There were only two definitions of iodine-deficient (water iodine concentration < 10 μg/L) and iodine-excess areas (water iodine concentration > 100 μg/L) in China before 2020. Areas with water iodine concentration between 10 and 100 μg/L implement the same policy as iodine-deficient areas to provide iodized salt. The definition of iodine-adequate areas was formulated in 2020 for the first time. The paper aims to investigate the coverage rate of iodized salt (CR) in different areas defined according to the latest national standards, evaluate the iodine status of local women, and provide a basis for the revision and improvement of relevant policies.

METHODS

A total of 1948 women aged 18-60 were recruited from the iodine extra-high areas (IEHA), iodine-excess areas (IEA), iodine-adequate areas (IAA), inland iodine-deficient areas (IIDA), and coastal iodine-deficient areas (CIDA). Information on daily diet was collected with the Food Frequency Questionnaire. Drinking water, salt, food, and urine samples were collected and tested in our laboratory. Based on the recommended daily iodine intake, we assessed whether the subjects' daily iodine intake levels were adequate.

RESULTS

The CR and the median urinary iodine concentrations (UICs) were 4.02% and 98.03 μg/L in CIDA, 89.74% and 144.93 μg/L in IIDA, 26.55% and 178.60 μg/L in IAA, 8.78% and 446.5 μg/L in IEA, 3.95% and 605.4 μg/L in IEHA, respectively. The differences among these five areas were statistically significant (P < 0.0001). The daily dietary iodine intakes were mainly from drinking water in IAA (63.92%), IEA (92.29%), and IEHA (92.93%), and were mainly from iodized salt in IIDA (59.22%) and food in CIDA (86.6%).

CONCLUSION

Women in IAA and IIDA were in an adequate iodine state. Women in IEA and IEHA were in an iodine-excess state, and it is necessary to carry out water improvements projects. Women in CIDA were in a slight iodine-deficient state, and health education on scientific iodine fortification should be strengthened to increase iodine intake.

Outcomes of a state-wide salt reduction initiative in adults living in Victoria, Australia

PURPOSE

To assess any effects of a state-wide sodium reduction intervention on sodium intake, sources of dietary sodium and discretionary salt use at a population level.

METHODS

Data (24-h urinary sodium excretion, self-report survey, a 24-h dietary recall) were collected cross-sectionally at baseline (2016/2017) and follow-up (2020) from adults in Victoria, Australia. Intervention activities included consumer awareness advertising campaign, public debate generation via mass media, strengthening existing policy initiatives and supporting food innovation with industry.

RESULTS

There were 339 participants at baseline and 211 at follow-up, with 144 and 90 of participants completing a 24-h dietary recall, respectively. There was no difference in adjusted 24-h urinary sodium excretion between baseline and follow-up (134 vs 131 mmol/24 h; p = 0.260). There were no differences in the percentage of participants adding salt during cooking (63% vs 68%; p = 0.244), adding salt at the table (34% vs 37%; p = 0.400) or regularly taking action to control salt/sodium intake (22% vs 21%; p = 0.793). There were large differences in the quantity of dietary sodium sourced from retail stores (57% vs 77%, p < 0.001), and less sodium was sourced from foods at fresh food markets (13% vs 2%; p ≤ 0.001) at follow-up. No large differences were apparent for foods with different levels of processing or for food groups.

CONCLUSION

There was no clear population-level effect of the 4-year multi-component Victorian Salt Reduction Intervention on sodium intake with Victorian adults continuing to consume sodium above recommended levels. The findings indicate that more intensive and sustained efforts aiming at the retail and food industry with national level support are likely to be required to achieve a measurable improvement in sodium intake at a state level.

Pertinence of Salt-Related Knowledge and Reported Behaviour on Salt Intake in Adults: A Cross-Sectional Study

The association between salt-related knowledge, attitude, behaviour (KAB) and actual salt consumption in Greek adults is uncertain. This study investigates the correlation between salt intake, gauged by 24-h urinary sodium excretion, with salt-related KAB. It further explores how socio-demographic factors influence these behaviors. Salt consumption was evaluated using a 24-h urinary sodium test, and compared to self-reported KAB data. Knowledge and behavior scores related to salt were computed. An overall cohort-adjusted model examined the relationship between daily salt consumption, knowledge and behavior scores, and certain covariates. Through the stratification by the cohort random effect, two models were established (Cohort I Adults; Cohort II Students) examining the same relationships of the overall cohort model. 463 Greek adults participated. The average salt intake was 9.54 g/day, nearly double the WHO recommendation. Significant differences in knowledge scores were noted based on sex, age, education, and BMI. A trend suggesting lower discretionary salt use with increased salt intake was observed (p = 0.06). However, comprehensive analysis revealed no direct correlation between salt intake and either knowledge (p = 0.562) or behavior scores (p = 0.210). The results emphasize the need for food product reforms by industry stakeholders and accelerated efforts towards reducing salt intake.

Estimating mean population salt intake using spot urine samples in Nepal: a cross-sectional study

INTRODUCTION

Little is known about the usefulness of spot urine testing compared with 24-h urine samples to estimate salt intake in low-income settings. This is given 24-h urinary collection can be costly, burdensome, and impractical in population surveys. The primary objective of the study was to compare urinary sodium levels (as an estimate of salt intake) of Nepalese population between 24-h urine and spot urine using previously established spot urine-based equations. Additionally, this study explored the 24-h prediction of creatinine and potassium excretion from spot urine samples using available prediction equations.

METHODS

The sample population was derived from the community-based survey conducted in Nepal in 2018. Mean salt intake was estimated from spot urine samples comparing previously published equations, and this was then contrasted with mean salt intake estimations from 24-h urine samples, using paired t test, Pearson correlation coefficient, intraclass correlation coefficient, and Bland-Altman plots.

RESULTS

A total of 451 participants provided both complete 24-h and morning spot urine samples. Unweighted mean (±SD) salt intake based on 24-h urine collection was 13.28 ± 4.72 g/day. The corresponding estimates were 15.44 ± 5.92 g/day for the Kawasaki, 11.06 ± 3.17 g/day for the Tanaka, 15.22 ± 16.72 g/day for the Mage, 10.66 ± 3.35 g/day for the Toft, 8.57 ± 1.72 g/day for the INTERSALT with potassium, 8.51 ± 1.73 g/day for the INTERSALT without potassium, 7.88 ± 1.94 g/day for the Whitton, 18.13 ± 19.92 g/day for the Uechi simple-mean and 12.07 ± 1.77 g/day using the Uechi regression. As compared with 24-h urine estimates, all equations showed significant mean differences (biases); the Uechi regression had the least difference with 9% underestimation (-1.21 g/day, P  < 0.001).Proportional biases were evident for all equations depending on the level of salt intake in the Bland-Altman plots.

CONCLUSION

None of the included spot urine-based equations accurately corresponded to 24-h salt intake in the present study. These equations may be useful for longitudinal monitoring of population salt intake in Nepal, our study highlights that there are limitations on using existing equations for estimating mean salt intake in Nepali population. Further studies are warranted for accuracy and validation.

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.

Twenty-four-hour Urinary Salt Excretion on Admission Predicts Significant Weight Loss with Seven-day Dietary Salt Restriction in Hospitalized Patients with Chronic Kidney Disease: A Single-center Study

In patients with chronic kidney disease (CKD), restricting dietary salt is recommended to prevent fluid retention. Rapid weight loss is often observed when CKD patients with a high salt intake are hospitalized and started on a low-salt diet. We investigated the effects of 7-day dietary salt restriction on weight loss in hospitalized patients with CKD. During the 7-day hospitalization, a low-salt (6 g/day) and low-protein (0.6-0.8 g/kg/day ideal body weight) diet was served to all patients. Urine samples were collected for the first 24 h after admission, and patients were divided into quartiles (Q1-Q4) by urinary salt excretion. Body weight was measured on days 1 and 7. Weight loss after admission was compared among the groups. Factors associated with weight loss were evaluated by multivariate logistic regression. The mean age of the patients was 70.3 ± 11.7 years, and 73% were male. Mean weight loss was 1.6 ± 1.7 kg on day 7. Weight loss was significantly greater in Q3 and Q4 than in Q1 (P = 0.009 and P <0.001, respectively). In the univariate analysis, weight loss correlated positively with 24-h urinary salt excretion on admission (γ2 = 0.146) and body mass index (γ2 = 0.223). The 24-h urinary salt excretion on admission and BMI were independently associated with weight loss of >2 kg. The adjusted odds ratios (95% confidence interval) were 1.24 (1.13-1.36) and 1.15 (1.07-1.22), respectively. Twenty-four-hour urinary salt excretion on admission is useful for predicting significant weight loss with short-term dietary salt restriction.

Estimating population level 24-h sodium excretion using spot urine samples in older adults in rural South Africa

BACKGROUND

South Africa has introduced regulations to reduce sodium in processed foods. Assessing salt consumption with 24-h urine collection is logistically challenging and expensive. We assess the accuracy of using spot urine samples to estimate 24-h urine sodium (24hrUNa) excretion at the population level in a cohort of older adults in rural South Africa.

METHODS

24hrUNa excretion was measured and compared to that estimated from matched spot urine samples in 399 individuals, aged 40-75 years, from rural Mpumalanga, South Africa. We used the Tanaka, Kawasaki, International Study of Sodium, Potassium, and Blood Pressure (INTERSALT), and Population Mean Volume (PMV) method to predict 24hrUNa at the individual and population level.

RESULTS

The population median 24hrUNa excretion from our samples collected in 2017 was 2.6 g (interquartile range: 1.53-4.21) equal to an average daily salt intake of 6.6 g, whereas 65.4% of participants had a salt excretion above the WHO recommended 5 g/day. Estimated population median 24hrUNa derived from the INTERSALT, both with and without potassium, showed a nonsignificant difference of 0.25 g (P = 0.59) and 0.21 g (P = 0.67), respectively. In contrast, the Tanaka, Kawasaki, and PMV formulas were markedly higher than the measured 24hrUNa, with a median difference of 0.51 g (P = 0.004), 0.99 g (P = 0.00), and 1.05 g (P = 0.00) respectively. All formulas however performed poorly when predicting an individual's 24hrUNa.

CONCLUSION

In this population, the INTERSALT formulas are a well suited and cost-effective alternative to 24-h urine collection for the evaluation of population median 24hrUNa excretion. This could play an important role for governments and public health agencies in evaluating local salt regulations and identifying at-risk populations.

Urinary metabolomics, dietary salt intake and blood pressure: the African-PREDICT study

In Black populations excessive salt intake may exacerbate the genetic predisposition to hypertension and promote the early onset of cardiovascular disease. Ethnic differences in the interaction between sodium intake and the metabolome may play a part in hypertension and cardiovascular disease development. We determined (1) urinary amino acid and acylcarnitine profiles of young Black and White adults according to low, moderate, and high dietary salt intake, and (2) investigated the triad of salt intake, systolic blood pressure (SBP), and the associated metabolomics profile. This study included 447 White and 380 Black adults aged 20-30 years from the African-PREDICT study. Estimated salt intake was determined from 24-hour urinary sodium levels. Urinary amino acids and acylcarnitines were measured using liquid chromatography-tandem mass spectrometry. Black adults exhibited no significant differences in SBP, amino acids, or acylcarnitines across low (<5g/day), moderate (5-10g/day), and high (>10g/day) salt intake. White adults with a high salt intake had elevated SBP compared to those with low or moderate intakes (p < 0.001). Furthermore, gamma-aminobutyric acid (GABA) (q = 0.020), citrulline (q = 0.020), glutamic acid (q = 0.046), serine (q = 0.054) and proline (q = 0.054) were lowest in those with higher salt intake. Only in White and not Black adults did we observe inverse associations of clinic SBP with GABA (Adj. R2 = 0.34; Std. β = -0.133; p = 0.003), serine (Adj. R2 = 0.33; Std. β = -0.109; p = 0.014) and proline (Adj. R2 = 0.33; Std. β = -0.109; p = 0.014). High salt intake in White, but not in black adults, were related to metabolomic changes and may contribute to pathophysiological mechanisms associated with increased BP.

Estimation of mean population salt intakes using spot urine samples and associations with body mass index, hypertension, raised blood sugar and hypercholesterolemia: Findings from STEPS Survey 2019, Nepal

Background

High dietary salt intake is recognized as a risk factor for several non-communicable diseases (NCDs), in particular cardiovascular diseases (CVDs), including heart attack and stroke. Accurate measurement of population level salt intake is essential for setting targeted goals and plans for salt reduction strategies. We used a spot urine sample to estimate the mean population salt intake in Nepal and evaluated the association of salt intake with excess weight, hypertension, raised blood sugar and hypercholesterolemia, and a number of socio-demographic characteristics.

Methods

A population-based cross-sectional study was carried out from February to May 2019 using a WHO STEPwise approach to surveillance. Spot urine was collected from 4361 participants aged 15–69 years for the analysis of salt intake. We then used the INTERSALT equation to calculate population salt intake. Student’s ‘t’ test, one-way ANOVA and multivariable linear regression were used to assess the association between salt intake and a number of factors. Statistical significance was accepted at P < .05.

Results

The average (±SD) age of participants was 40 (14.1) years. Mean salt intake, derived from spot urine samples, was estimated to be 9.1g/d. A total of 70.8% of the population consumed more than the WHO’s recommended amount of 5g salt per day, with almost one third of the population (29%) consuming more than 10g of salt per day. Higher salt intake was significantly associated with male gender (β for male = 0.98g; 95%CI:0.87,1.1) and younger age groups (β25–39 years = 0.08; 95%CI:-0.08,0.23) and higher BMI (β = 0.19; 95%CI:0.18,0.21). Participants who were hypertensive and had raised blood cholesterol consumed less salt than people who had normal blood pressure and cholesterol levels (P<0.001).

Conclusions

Salt consumption in Nepal is high, with a total of 70.8% of the population having a mean salt intake >5g/d, well above the World Health Organization recommendation. High salt intake was found to be associated with sex, age group, education, province, BMI, and raised cholesterol level of participants These findings build a strong case for action to reduce salt consumption in Nepal in order to achieve the global target of 30% reduction in population salt intake by 2025.

The DONALD study as a longitudinal sensor of nutritional developments: iodine and salt intake over more than 30 years in German children

Purpose

Mild-to-moderate iodine deficiency was present in large parts of Germany up to the beginning 1990s and improved from then on. Current epidemiological data on spot urine iodine measurements in German children strongly suggest the re-occurrence of an impaired iodine status. We thus examined whether this re-occurrence is identifiable in more detail, through iodine analyses of 24-h urine samples of a well-characterized cohort of German children in whom samples have been systematically collected from 1985 onward. As iodized salt is a major source for iodine supply, urinary sodium excretion was additionally studied.

Methods

Daily iodine and sodium excretions were measured in 2600 24-h urine samples collected between 1985 and 2018 by 677 healthy children aged 6–12 years (participants of the DONALD study). These data were compared with 24-h iodine and sodium excretion estimates obtained from spot urine samples collected in the representative German Health Interview and Examination Surveys for Children and Adolescents KiGGS-baseline (2003–2006) and KiGGS-wave-2 (2014–2017).

Results

Between 1985 and1992, DONALD participants started with a median daily iodine excretion level of 40.1 µg/d. Then, during 1993–2003, iodine excretions mounted up to an approximate plateau (~ 84.8 µg/d). This plateau lasted until 2012. Thereafter, iodine concentrations started to decrease again resulting in a median iodine excretion of only 58.9 µg/d in 2018. Sodium excretion, however, had increased. The marked decrease in iodine status along with an abundant sodium excretion corresponded closely with nationwide KiGGS data.

Conclusions

As exemplified for the clearly worsening iodine status in German children, longitudinal cohort studies collecting detailed biomarker-based prospective data have the potential to reliably capture health-relevant nutritional changes and trends, applicable on a more comprehensive and even representative population level.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-022-02801-6.

Factors Associated With the Use of a Salt Substitute in Rural China

IMPORTANCE

Lowering sodium intake reduces blood pressure and may reduce the risk of cardiovascular diseases. The use of reduced-sodium salt (a salt substitute) may achieve sodium reduction, but its effectiveness may be associated with the context of its use.

OBJECTIVE

To identify factors associated with the use of salt substitutes in rural populations in China within the Salt Substitute and Stroke Study, a large-scale cluster randomized trial.

DESIGN, SETTING, AND PARTICIPANTS

This sequential mixed-methods qualitative evaluation, conducted from July 2 to August 28, 2018, in rural communities across 3 provinces in China, included a quantitative survey, collection of 24-hour urine samples, and face-to-face interviews. A random subsample of trial participants, selected from the 3 provinces, completed the quantitative survey (n = 1170) and provided urine samples (n = 1025). Interview respondents were purposively selected from the intervention group based on their different ranges of urinary sodium excretion levels. Statistical analysis was performed from September 18, 2018, to February 22, 2019.

EXPOSURES

The intervention group of the Salt Substitute and Stroke Study was provided with the free salt substitute while the control group continued to use regular salt.

MAIN OUTCOMES AND MEASURES

Knowledge, attitudes, and behaviors regarding the use of the salt substitute were measured using quantitative surveys, and urinary sodium levels were measured using 24-hour urine samples. Contextual factors were explored through semistructured interviews and integrated findings from surveys and interviews.

RESULTS

A total of 1170 individuals participated in the quantitative survey. Among the 1025 participants with successful urine samples, the mean (SD) age was 67.4 (7.5) years, and 502 (49.0%) were female. The estimated salt intake of participants who believed that high salt intake was good for health was higher; however, it was not significantly different (0.84 g/d [95% CI, -0.04 to 1.72 g/d]) from those who believed that high salt intake was bad for health. Thirty individuals participated in the qualitative interviews (18 women [60.0%]; mean [SD] age, 70.3 [6.0] years). Quantitative and qualitative data indicated high acceptability of and adherence to the salt substitute. Contextual factors negatively associated with the use of the salt substitute included a lack of knowledge about the benefits associated with salt reduction and consumption of high-sodium pickled foods. In addition, reduced antihypertensive medication was reported by a few participants using the salt substitute.

CONCLUSIONS AND RELEVANCE

This study suggests that lack of comprehensive understanding of sodium reduction and salt substitutes and habitual consumption of high-sodium foods (such as pickled foods) were the main barriers to the use of salt substitutes to reduce sodium intake. These factors should be considered in future population-based, sodium-reduction interventions.

Iodine supplementation for pregnant women: a cross-sectional national interventional study

BACKGROUND

Although Iran has been considered iodine replete since 2000, the first national survey of iodine intake among Iranian pregnant women in 2014 indicated that despite the adequate intake of iodine by the general population, this vulnerable group has moderate iodine deficiency. Therefore, in this national cross-sectional interventional study, we aimed to assess the iodine intake and thyroid function of Iranian pregnant women 2 years after implementing national iodine supplementation for this vulnerable group.

MATERIALS AND METHODS

In this cross-sectional study, we conducted a national interventional survey of pregnant women. A total of 1200 pregnant women (400 women from each trimester) from 12 provinces of Iran were recruited from the antenatal care clinics from October 2018 to March 2019. The median urinary iodine concentration (MUIC), as an indicator of iodine status in three spot urine samples, was measured, along with the serum total T4 (TT4), thyrotropin (TSH), thyroglobulin (Tg), thyroid peroxidase antibody (TPO-Ab), and iodine content of household salt.

RESULTS

The mean age of the cohort was 28 ± 6.2 years, with the mean gestational age of 22.7 ± 13.0 weeks. The overall MUIC (IQR) of pregnant women was 188 µg/L (124.2-263 µg/L). Also, the MUICs in the three trimesters of pregnancy were 174 µg/L (110-254), 175 µg/L (116-251), and 165 µg/L (114-235), respectively. The MUICs ≥ 150, 100-149, and < 100 µg/L were found in 63, 19.8, and 16.2% of the subjects, respectively. The mean TT4 level was 12 ± 4.5 µg/dL, and the median (IQR) level of TSH was 2.37 mIU/L (1.66-3.18 mIU/L). According to our local reference range, 118 (10.5%) pregnant women had subclinical hypothyroidism, 6 (0.53%) women had isolated hypothyroxinemia, and 65 (5.7%) women were TPO-Ab positive. Also, the median (IQR) level of Tg was 10.08 µg/dL (5.7-20.4 µg/dL), and the median iodine content of household salt was 29.6 µg/g; the iodine content was ≥ 30 µg/g in 85% of household salt. The results showed that more than 95% of households were under iodized salt coverage.

CONCLUSION

The results of this study indicated that iodine supplementation with at least 150 µg of iodine per day improved the iodine intake of pregnant women. Except for subclinical hypothyroidism, the prevalence of clinical hypothyroidism, clinical/subclinical thyrotoxicosis, TPO-Ab positivity, and isolated hypothyroxinemia decreased significantly, which emphasizes the importance of iodine supplementation during pregnancy.

Association of Estimated Salt and Miso Intake with the Prevalence of Obesity in People with Type 2 Diabetes: A Cross-Sectional Study

Salt intake is often estimated by the amount of sodium excreted in urine, and miso has been reported to increase it. This cross-sectional study investigated the relationship between obesity and high estimated salt intake with and without habitual miso consumption. Estimates of salt intake (g/day) were calculated using urinary sodium excretion, and a high estimated intake was defined as greater than the median amount of 9.5 g/day. Participants were divided into four groups based on estimated salt intake and miso consumption. Among 300 people, the proportions of obesity were 77.8% (n = 14/18), 40.2% (n = 53/132), 26.0% (n = 33/127), and 34.8% (n = 8/23) in the (+/-), (+/+), (-/+), and (-/-) groups of high estimated salt intake/habitual miso consumption, respectively. Compared with the (+/-) group, the adjusted odds ratios for obesity were 0.07 (95% confidence interval (CI): 0.02-0.26, p < 0.001), 0.16 (95% CI: 0.03-0.76, p = 0.022), and 0.14 (95% CI: 0.04-0.51, p = 0.003) in the (-/+), (-/-), and (+/+) groups, respectively. The presence of obesity was not much higher in people with high estimated salt intake with habitual miso consumption than that in people without. Clinicians should be aware that miso consumption promotes salt excretion, which may lead to an apparently higher estimated salt intake than actual.

Trend of salt intake measured by 24-h urine collection in the Italian adult population between the 2008 and 2018 CUORE project surveys

BACKGROUND AND AIMS

The WHO Global Action Plan for the Prevention of non-communicable diseases (NCDs) recommends a 30% relative reduction in mean population salt/sodium intake. The study assessed the trend in the habitual salt intake of the Italian adult population from 2008 to 2012 to 2018-2019 based on 24-h urinary sodium excretion, in the framework of the CUORE Project/MINISAL-GIRCSI/MENO SALE PIU' SALUTE national surveys.

METHODS AND RESULTS

Data were from cross-sectional surveys of randomly selected age and sex-stratified samples of resident persons aged 35-74 years in 10 (out of 20) Italian Regions distributed in North, Centre and South of the Country. Urinary sodium and creatinine measurements were carried out in a central laboratory. The analyses included 942 men and 916 women examined in 2008-2012, and 967 men and 1010 women examined in 2018-2019. The age-standardized mean daily population salt (sodium chloride) intake was 10.8 g (95% CI 10.5-11.1) in men and 8.3 g (8.1-8.5) in women in 2008-2012 and respectively 9.5 g (9.3-9.8) and 7.2 g (7.0-7.4) in 2018-2019. A statistically significant (p<0.0001) salt intake reduction was thus observed over 10 years for both genders, and all age, body mass index (BMI) and educational classes.

CONCLUSIONS

The average daily salt intake of the Italian general adult population remains higher than the WHO recommended level, but a significant reduction of 12% in men and 13% in women has occurred in the past ten years. These results encourage the initiatives undertaken by the Italian Ministry of Health aimed at the reduction of salt intake at the population level.

High salt intake induces collecting duct HDAC1-dependent NO signaling

We reported that high salt (HS) intake stimulates renal collecting duct (CD) endothelin (ET) type B receptor (ETBR)/nitric oxide (NO) synthase 1β (NOS1β)-dependent NO production inhibiting the epithelial sodium channel (ENaC) promoting natriuresis. However, the mechanism underlying the HS-induced increase of NO production is unclear. Histone deacetylase 1 (HDAC1) responds to increased fluid flow, as can occur in the CD during HS intake. The renal inner medulla (IM), in particular the IMCD, has the highest NOS1 activity within the kidney. Hence, we hypothesized that HS intake provokes HDAC1 activation of NO production in the IM. HS intake for 1 wk significantly increased HDAC1 abundance in the IM. Ex vivo treatment of dissociated IM from HS-fed mice with a selective HDAC1 inhibitor (MS-275) decreased NO production with no change in ET-1 peptide or mRNA levels. We further investigated the role of the ET-1/ETBR/NOS1β signaling pathway with chronic ETBR blockade (A-192621). Although NO was decreased and ET-1 levels were elevated in the dissociated IM from HS-fed mice treated with A-192621, ex vivo MS-275 did not further change NO or ET-1 levels suggesting that HDAC1-mediated NO production is regulated at the level or downstream of ETBR activation. In split-open CDs from HS-fed mice, patch clamp analysis revealed significantly higher ENaC activity after MS-275 pretreatment, which was abrogated by an exogenous NO donor. Moreover, flow-induced increases in mIMCD-3 cell NO production were blunted by HDAC1 or calcium inhibition. Taken together, these findings indicate that HS intake induces HDAC1-dependent activation of the ETBR/NO pathway contributing to the natriuretic response.

Effect of workplace dietary intervention on salt intake and sodium-to-potassium ratio of Japanese employees: A quasi-experimental study

OBJECTIVES

Excess salt intake is a major risk factor for hypertension and cardiovascular disease. Modifying workplace environments has been recognized to be important for reducing salt intake. However, studies examining the effects of improving the workplace environment regarding salt reduction are limited. This study aimed to evaluate the effects of workplace dietary intervention on employees' salt intake and sodium-to-potassium (Na/K) ratio.

METHODS

A quasi-experimental study was conducted. Two small business establishments in Saitama Prefecture, Japan, were allocated as the intervention (n = 69) and comparison (n = 68) workplaces, respectively. The 1-year intervention involving healthy lunch and nutrition education was implemented in the intervention workplace. Spot urine samples, physical assessments, and self-administered questionnaire data were collected at baseline, 6 months, and 1 year after the start of the intervention. Analysis of covariance was conducted to investigate differences in the salt intake or Na/K ratio between the study workplaces at year 1. Educational status and rotating work schedules were included as covariates.

RESULTS

Salt intake in the intervention workplace decreased significantly from 10.7 to 9.3 g (-1.4 g change; 95% confidence interval [CI]: "-2.4, -0.5"). The adjusted difference in changes in salt intake between workplaces was statistically significant (-3.7 g change; 95% CI: "-5.2, -2.3"). Although no significant change was observed in the Na/K ratio in the intervention workplace (3.37-3.08; -0.29 change; 95% CI: "-0.59, 0.01"), the adjusted difference in changes between the workplaces was statistically significant (-0.60 change; 95% CI: "-1.03, -0.17").

CONCLUSIONS

Providing healthy lunch and nutrition education may be effective approaches to reduce employees' salt intake and Na/K ratio.

Correcting for Intra-Individual Variability in Sodium Excretion in Spot Urine Samples Does Not Improve the Ability to Predict 24 h Urinary Sodium Excretion

Given a global focus on salt reduction efforts to reduce cardiovascular risk, it is important to obtain accurate measures of salt intake on a population level. This study determined firstly whether adjustment for intra-individual variation in urinary sodium (Na) excretion using three repeated 24 h collections affects daily estimates and whether the use of repeated spot urine samples results in better prediction of 24 h Na compared to a single collection. Twenty three community-dwelling men and women from South Africa (mean age 59.7 years (SD = 15.6)) participating in the World Health Organization Study on global AGEing and adult health (WHO-SAGE) Wave 3 study collected 24 h and spot early morning urine samples over three consecutive days to assess urinary Na excretion. INTERSALT, Tanaka, and Kawasaki prediction equations, with either average or adjusted spot Na values, were used to estimate 24 h Na and compared these against measured 24 h urinary Na. Adjustment was performed by using the ratio of between-person (sb) and total (sobs) variability obtained from repeated measures analysis of variance. Sensitivity of the equations to predict daily urinary Na values below 5 g salt equivalent was calculated. The sb/sobs for urinary Na using three repeated samples for spot and 24 h samples were 0.706 and 0.798, respectively. Correction using analysis of variance for 3 × 24 h collections resulted in contraction of the upper end of the distribution curve (90th centile: 157 to 136 mmoL/day; 95th centile: 220 to 178 mmoL/day). All three prediction equations grossly over-estimated 24 h urinary Na excretion, regardless of whether a single spot urine or repeated collections corrected for intra-individual variation were used. Sensitivity of equations to detect salt intake equivalent values of ≤5 g/day was 13% for INTERSALT, while the other two equations had zero sensitivity. Correcting for intra-individual variability in Na excretion using three 24 h urine collections contracted the distribution curve for high intakes. Repeated collection of spot samples for urinary Na analysis does not improve the accuracy of predicting 24 h Na excretion. Spot urine samples are not appropriate to detect participants with salt intakes below the recommended 5 g/day.

Correlation among high salt intake, blood pressure variability, and target organ damage in patients with essential hypertension: Study protocol clinical trial (SPIRIT compliant)

BACKGROUND

Essential hypertension is a multifactorial disease, which is affected by genetic and environmental factors, and can cause diseases such as cerebrovascular disease, heart failure, coronary heart disease, and chronic renal failure. High salt intake is a risk factor for hypertension, stroke, and cardiovascular disease. Blood pressure variability (BPV) is a reliable independent predictor of cardiovascular events and death. At present, there are few studies about the correlation among high salt intake, BPV, and target organ damage (TOD) in patients with hypertension.

OBJECTIVE

The purpose of this study is to compare 24-hour urine sodium excretion, BPV, carotid intima-media thickness, left ventricular mass index, and serum creatinine or endogenous creatinine clearance rate. To clarify the relationship between high salt load and BPV and TOD in patients with hypertension.This study is a cross-sectional study. It will recruit 600 patients with essential hypertension in the outpatient and inpatient department of cardiovascular medicine of Chengdu Fifth People's Hospital. Researchers will obtain blood and urine samples with the patient's informed consent. In addition, we will measure patient's blood pressure and target organ-related information.

TRIAL REGISTRY

The study protocol was approved by the Chengdu Fifth People's Hospital. Written informed consent will be obtained from all the participants. The trial was registered in the Chinese Clinical trial registry, ChiCTR2000029243. This trial will provide for the correlation among high salt intake, BPV, and TOD in patients with essential hypertension.

Stopping the supply of iodized salt alone is not enough to make iodine nutrition suitable for children in higher water iodine areas: A cross-sectional study in northern China

BACKGROUND

For the sake of children's health, iodized salt supply has been stopped in many areas with excessive iodine in the drinking water, but children's iodine nutrition status and thyroid function after terminating the iodized salt supply is unknown. Objective We assessed the iodine nutrition, thyroid function and influencing factors for thyroid abnormalities in children from areas with different concentrations of water iodine; the supply of iodized salt has been stopped in high water iodine areas. This study aimed to evaluate whether the strategy of stopping the supplies of iodized salt alone is enough to avoid thyroid dysfunction in all areas with excess water iodine while still meeting the iodine nutrition needs of children.

METHODS

A cross-sectional study was conducted in children from four areas with different drinking water iodine concentrations in Tianjin, China. The drinking water samplings and spot urine samples were collected to estimate the external and internal iodine exposure levels. The thyroid volume was measured, and blood samples were collected to assess thyroid function. Logistic regression analysis was used to analyze risk factors for thyroid abnormalities. A dietary survey was conducted to determine the sources of iodine nutrition among the areas with different iodine concentrations in the drinking water.

RESULTS

In the area with a drinking water iodine concentration ≥300 μg/L, the median urinary iodine concentration (UIC) in children was 476.30 (332.20-639.30) μg/L, which was higher than that in other groups (all P < 0.05), and the prevalence of thyroid nodules and the thyroid goiter rate were higher than those in the <100 μg/L, 100-150 μg/L and 150-300 μg/L areas (all P < 0.01). Binary logistic regression analysis indicated that the risk of thyroid abnormalities was significantly increased in the UIC 200-299 μg/L group (OR: 4.534; 95% CI: 1.565, 13.135; bootstrapped 95% CI: 1.689, 21.206, P = 0.004) and in the UIC ≥ 300 μg/L group (OR: 6.962; 95% CI: 2.490, 19.460; bootstrapped 95% CI: 2.838, 32.570, P = 0.001) compared to the 100-199 μg/L group. The iodine contribution rates from water in areas with water iodine concentrations ≥300 μg/L are up to 63.04%.

CONCLUSIONS

After termination of the iodized salt supply, the level of iodine nutrition of children in the area with drinking water iodine concentrations ≥300 μg/L is still excessive. The water source needs to be replaced in this area. In the area with a water iodine concentration of 150-300 μg/L, it is proposed that stopping the supply of iodized salt is sufficient to achieve the proper iodine nutrition status in children.

The association of parents' behaviors related to salt with 24 h urinary sodium excretion of their children: A Spanish cross-sectional study

BACKGROUND

Sodium intake is excessive among Spanish children, but the salt use behaviors of parents and children are unknown. This study aims to determine behaviors related to salt intake in both schoolchildren and parents and the relationship between parental behaviors and 24 h urinary sodium excretion (UNa-24h) in children.

SUBJECTS AND METHODS

A convenience sample was taken from a cross-sectional analysis. Parents completed a self-reported questionnaire about their behaviors related to salt, and their responses were compared with the UNa-24h of their own children. The median test was used to identify differences in UNa-24h according to behaviors. Logistic regression was used to assess the relationship between the behaviors of parents and high sodium excretion in the children and the risk of children's use of table salt, adjusting for age, sex, and BMI. Multinomial logistic regression models, adjusted by the covariates, were used to study the children's salt preferences.

RESULTS

A total of 329 schoolchildren from different Spanish provinces were included in the study (mean age: 9.0 ± 1.2 years, 157 girls). The majority of families (parents mean age: 42.0 ± 5.2 years) reported adding salt to food during cooking (92%), and 59% of them never looked at the sodium content on food labels. However, none of these behaviors were related to UNa-24h (p > 0.05). The use of iodized salt (53%), the presence of a salt shaker on the table (6%), and the use of table salt by fathers (57%), mothers (52%) or children (17%) increased the odds (p < 0.05) of children having a higher UNa-24h. Checking sodium content on food labels and the use of table salt by the children or father was associated with a lower preference for salty foods (p < 0.05).

CONCLUSIONS

It is important to make parents aware of the relationship between their behaviors regarding the use of discretionary salt and their children's sodium intake. Our data suggest that salt-specific education programs on how to reduce salt both in-home and outside the home should be implemented to improve behavior skills related to salt consumption in parents and children.