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.

Association of Pro-Inflammatory Diet with Long-Term Risk of All-Cause and Cardiovascular Disease Mortality: NIPPON DATA80

AIM

A pro-inflammatory diet may increase the risk of cardiovascular disease (CVD) and all-cause mortality. However, this remains inconclusive as there is yet no study using a dietary record method that has been conducted in a large general population. Furthermore, an underestimation of the pro-inflammatory diet may exist due to the unmeasured effect of salt intake. Thus, in this study, we aimed to examine how pro-inflammatory diet is associated with the long-term risk of all-cause and CVD mortality in a representative Japanese population.

METHODS

A national nutrition survey was conducted throughout Japan in 1980. After considering the exclusion criteria, 9284 individuals (56% women aged 30-92 years) were included in this study. In total, 20 dietary parameters derived from 3-day weighed dietary records were used to calculate the dietary inflammatory index (DII). The causes of death were monitored until 2009. The Cox proportional hazards model was used to determine multivariable-adjusted hazard ratios (HRs). Stratified analysis according to salt intake level was also performed.

RESULTS

Compared with the lowest quartile of DII, multivariable-adjusted HRs (95% confidence intervals) in the highest quartile were 1.28 (1.15, 1.41), 1.35 (1.14, 1.60), 1.48 (1.15, 1.92), 1.62 (1.11, 2.38), and 1.34 (1.03, 1.75) for all-cause mortality, CVD mortality, atherosclerotic CVD mortality, coronary heart disease mortality, and stroke mortality, respectively. Stratified analysis revealed stronger associations among individuals with higher salt intake.

CONCLUSIONS

As per our findings, a pro-inflammatory diet was determined to be positively associated with the long-term risk of all-cause and CVD mortality in a representative Japanese population. Thus, considering both salt intake and pro-inflammatory diet is deemed crucial for a comprehensive assessment of CVD risk.

Is high salt intake inducing obesity via production of cortisol? A novel working hypothesis and pilot study

PURPOSE

Evidence is growing that high salt intake is an independent risk factor for obesity, but the mechanisms are unknown. Our novel working hypothesis is that high salt intake drives cortisol production, which in turn, drives obesity. The current study aimed to demonstrate an acute cortisol response following a single high salt meal.

METHODS

Eight participants (age 30.5 ± 9.8 years [mean ± SD], 50% female), consumed high salt (3.82 g; 1529 mg sodium) and low salt (0.02 g; 9 mg sodium) meals in a randomized cross-over design.

RESULTS

Urinary and salivary cortisol and plasma adrenocorticotropic hormone (ACTH) demonstrated order effects. When high salt was given second, there was a peak above baseline for urinary cortisol (26.3%), salivary cortisol (9.4%) and plasma ACTH (4.1%) followed by a significant decline in each hormone (treatment*time, F[9, 18] = 2.641, p = 0.038, partial η2 = 0.569; treatment*time, F[12, 24] = 2.668, p = 0.020, partial η2 = 0.572; treatment*time, F[12, 24] = 2.580, p = 0.023, partial η2 = 0.563, respectively), but not when high salt was given first (p > 0.05 for all).

CONCLUSION

These intriguing findings provide partial support for our hypothesis and support a need for further research to elucidate the role of high salt intake in cortisol production and, in turn, in the aetiology of obesity.

TRIAL REGISTRATION NUMBER

ACTRN12623000490673; date of registration 12/05/2023; retrospectively registered.

Low-Chloride Diet Prevents the Development of Arterial Hypertension and Protects Kidney Function in Angiotensin II-Infused Mice

INTRODUCTION

A comprehensive pathophysiological mechanism to explain the relationship between high-salt intake and hypertension remains undefined. Evidence suggests that chloride, as the accompanying anion of sodium in dietary salt, is necessary to develop hypertension. We evaluated whether reducing dietary Cl- while keeping a standard Na+ intake modified blood pressure, cardiac hypertrophy, renal function, and vascular contractility after angiotensin II (AngII) infusion.

METHODS

C56BL/6J mice fed with standard Cl- diet or a low-Cl- diet (equimolar substitution of Cl- by a mixture of Na+ salts, both diets with standard Na+ content) received AngII (infusion of 1.5 mg/kg/day) or vehicle for 14 days. We measured systolic blood pressure (SBP), glomerular filtration rate (GFR), natriuretic response to acute saline load, and contractility of aortic rings from mice infused with vehicle and AngII, in standard and low-Cl- diet.

RESULTS

The mice fed the standard diet presented increased SBP and cardiac hypertrophy after AngII infusion. In contrast, low-Cl- diet prevented the increase of SBP and cardiac hypertrophy. AngII-infused mice fed a standard diet presented hampered natriuretic response to saline load, meanwhile the low-Cl- diet preserved natriuretic response in AngII-infused mice, without change in GFR. Aortic rings from mice fed with standard diet or low-Cl- diet and infused with AngII presented a similar contractile response.

CONCLUSION

We conclude that the reduction in dietary Cl- as the accompanying anion of sodium in salt is protective from AngII pro-hypertensive actions due to a beneficial effect on kidney function and preserved natriuresis.

Estradiol modulation of behavioral and physiological body fluid control during repeated dietary sodium deprivation

The low salt diet is a first line treatment for hypertension, but it is a difficult diet to maintain. As a result, patients may alternate between periods of high and low salt intake, the effects of which are unclear. Importantly, blood pressure increases in women after menopause, suggesting that estrogen plays a role in preventing hypertension. At present, however, it is unknown if the behavioral and physiological impact of alternating episodes on the low salt diet may be altered by the presence of estrogen. Our goals were to assess salt intake and body fluid hormones with repeated dietary sodium deprivations. Using ovariectomized rats with (EB) and without (OIL) estrogen treatment, we subjected rats to one or two dietary sodium deprivations using low salt laboratory chow. 0.5 M NaCl and water intakes were recorded after each period of regular chow or deprivation. After deprivation, rats were sacrificed, and trunk blood was collected for analysis of vasopressin, norepinephrine, epinephrine, and aldosterone levels. Plasma sodium concentration, plasma protein concentration, body weight, and uterine weight were also measured. There was no difference in the salt intakes of OIL- or EB-treated rats after one or two dietary sodium deprivations. However, EB-treated rats drank a less concentrated solution overall, suggesting less overcompensation after dietary sodium deprivation. Additionally, after a single episode of dietary sodium deprivation, EB-treated rats' consumption remained elevated above baseline even after returning to regular laboratory chow. These behavioral differences were not explained by alterations in vasopressin, norepinephrine, epinephrine, or aldosterone. Plasma sodium and plasma protein concentrations also did not show alterations related to the change in behavior. Further research is necessary to determine the mechanism behind these changes in intake in EB-treated rats, which may ultimately be clinically relevant for both pre- and postmenopausal women on the low salt diet.

Sodium intake and urinary losses in children on dialysis: a European multicenter prospective study

BACKGROUND

Sodium (Na) balance is unexplored in dialyzed children. We assessed a simplified sodium balance (sNaB) and its correlates in pediatric patients receiving maintenance dialysis.

METHODS

Patients < 18 years old on hemodialysis (HD) or peritoneal dialysis (PD) in six European Pediatric Dialysis Working Group centers were recruited. sNaB was calculated from enteral Na, obtained by a 3-day diet diary, Na intake from medications, and 24-h urinary Na (uNa). Primary outcomes were systolic blood pressure and diastolic blood pressure standard deviation scores (SBP and DBP SDS), obtained by 24-h ambulatory blood pressure monitoring or office BP according to age, and interdialytic weight gain (IDWG).

RESULTS

Forty-one patients (31 HD), with a median age of 13.3 (IQR 5.2) years, were enrolled. Twelve patients (29.3%) received Na-containing drugs, accounting for 0.6 (0.7) mEq/kg/day. Median total Na intake was 1.5 (1.1) mEq/kg/day, corresponding to 60.6% of the maximum recommended daily intake for healthy children. Median uNa and sNaB were 0.6 (1.8) mEq/kg/day and 0.9 (1.7) mEq/kg/day, respectively. The strongest independent predictor of sNaB in the cohort was urine output. In patients receiving HD, sNaB correlated with IDWG, pre-HD DBP, and first-hour refill index, a volume index based on blood volume monitoring. sNaB was the strongest predictor of IDWG in multiple regression analysis (β = 0.63; p = 0.005). Neither SBP SDS nor DBP SDS correlated with sNaB.

CONCLUSIONS

Na intake is higher than uNa in children on dialysis, and medications may be an important source of Na. sNaB is best predicted by urine output in the population, and it is a significant independent predictor of IDWG in children on HD. A higher resolution version of the Graphical abstract is available as Supplementary information.

The high salt intake in adults with metabolic syndrome is related to increased waist circumference and blood pressure: the Brazilian Longitudinal Study of Adult Health study (ELSA-Brasil)

OBJECTIVES

The association between metabolic syndrome (MetS), a cluster of cardiometabolic risk factors, and salt consumption has fed intense debate in recent years, although it is yet to be fully elucidated. We aimed to evaluate whether individuals with MetS have a high salt consumption and to identify which components of the MetS diagnosis could be independently related to high salt consumption.

METHODS

We analyzed data from 11 982 adults, ages 35 to 74 y, from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) cohort study, from which clinical and anthropometric data were assessed, and a validated 12-h overnight urine collection was used to estimate salt intake. MetS was defined according to the Adult Treatment Panel III criteria.

RESULTS

Salt intake was increased in individuals with MetS compared with individuals without MetS, regardless of sex (men: 14.3 ± 6.4 g/d versus 12.2 ± 5.5 g/d, P < 0.001; women: 10.6 ± 4.9 g/d versus 8.9 ± 4.0 g/d, P < 0.001) and increased progressively as the MetS criteria accumulated. The high salt intake in MetS participants, however, was observed only in the presence of elevated waist circumference and/or blood pressure and not with the other MetS criteria (reduced high-density lipoprotein, increased triglycerides, and impaired fasting blood glucose), regardless of the presence of MetS. When diabetes was incorporated as a MetS criterion, increased salt intake was observed in men but not in women.

CONCLUSIONS

Salt intake should be reduced worldwide, but strategies must be more intense in people with elevated blood pressure and waist circumference, regardless of MetS diagnosis, to avoid the associated morbidity and mortality.

Hypertension in urban slums of southern India: Burden, awareness, health seeking, control and risk factor profile

INTRODUCTION

Hypertension is the leading risk factor for global disease burden. Inequalities in health among urban poor and non-poor is a matter of concern. The current study was done to estimate the prevalence of hypertension and to describe the health seeking and risk factor profile of people with hypertension in the urban slums of Kochi, Kerala, India.

METHODS

Blood pressure of 5980 adults from 20 randomly selected slums were measured by door to door survey by trained nurses as a part of baseline assessment for a cluster randomised controlled trial.

RESULTS

Prevalence of hypertension was found to be 34.8% (95% CI 33.5-34.9). Among those with hypertension, 66.9% were aware of their hypertensive status, of which 75.8% were initiated on treatment for hypertension. Proportion of hypertensive in the population who had their blood pressure under control was 24.5%. Among hypertensive, 53% were obese, 25.1% had diabetes mellitus, 14% had history of hospitalisation for high blood pressure. Of them, 60.3% had a per capita salt consumption above 8 g/day and 47.5% of them reported sitting for more than 8 h on a usual day. Mean monthly out of pocket expenditure for treatment of hypertension was $9(Median $8, IQR $16).

CONCLUSION

One in three adults in urban slums of Kochi had hypertension. High rates of obesity, salt intake, physical inactivity prevails among the people with hypertension. Awareness, treatment initiation and control rate of hypertension are lower in urban slums as compared to non-slum urban areas. Slums require additional attention to ensure equitable and universal access to hypertension control.

Excessive salt intake accelerates the progression of cerebral small vessel disease in older adults

BACKGROUND

It is unclear whether excessive salt intake accelerates the progression of cerebral small vessel disease (CSVD). The major objective of this study was to investigate the harmful effect of excessive salt intake on the progression of CSVD in older individuals.

METHODS

Between May 2007 and November 2010, 423 community-dwelling individuals aged 60 years and older were recruited from the Shandong area, China. Salt intake was estimated using 24-hour urine collection for 7 consecutive days at baseline. Participants were classified into low, mild, moderate and high groups according to the salt intake estimation. CSVD including white matter hyperintensities (WMHs), lacunes, microbleeds and an enlarged perivascular space (EPVS) were determined using brain magnetic resonance imaging.

RESULTS

During an average of five years of follow-up, the WMH volume and WMH-to-intracranial ratio were increased in the four groups. However, the increasing trends in the WMH volume and WMH-to-intracranial ratio were significantly faster in the higher salt intake groups compared with the lower salt intake groups (P_adjusted < 0.001). The cumulative hazard ratios of new-incident WMHs (defined as those with Fazekas scale scores ≥ 2), new-incident lacunes, microbleeds or an EPVS, as well as composites of CSVD, were respectively 2.47, 2.50, 3.33, 2.70 and 2.89 for the mild group; 3.72, 3.74, 4.66, 4.01 and 4.49 for the moderate group; and 7.39, 5.82, 7.00, 6.40 and 6.61 for the high group, compared with the low group after adjustment for confounders (P_adjusted < 0.001). The risk of new-incident WMHs, lacunes, microbleeds or an EPVS, and composites of CSVD was significantly increased with each 1-standard-deviation increment in salt intake (P_adjusted < 0.001).

CONCLUSION

Our data indicates that excessive salt intake is an important and independent contributor to the progression of CVSD in older adults.

Iodine intake assessment in the staff of a Porto region university (Portugal): the iMC Salt trial

PURPOSE

Iodine deficiency disorder (IDD) is an ongoing worldwide recognized problem with over two billion individuals having insufficient iodine intake. School-aged children and pregnant women are often target groups for epidemiological studies, but there is a lack of knowledge on the general adult population. The aim of this study was to assess the iodine status among a Portuguese public university staff as a proxy for the adult working population.

METHODS

The population study covered 103 adults within the iMC Salt randomized clinical trial, aged 24-69 years. Urinary iodine concentration was measured spectrophotometrically using the Sandell-Kolthoff reaction. Iodine food intake was assessed using a 24-h dietary recall. The contribution of discretionary salt to the iodine daily intake was assessed through 24-h urinary sodium excretion (UIE) and potentiometric iodine determination of household salt.

RESULTS

The mean urine volume in 24 h was 1.5 L. The median daily iodine intake estimated from 24-h UIE was 113 µg/day, being lower among women (p < 0.05). Only 22% of participants showed iodine intake above the WHO-recommended cutoff (150 µg/day). The median daily iodine intake estimated from the 24-h dietary recall was 58 µg/day (51 and 68 µg/day in women and men, respectively). Dairy, including yoghurt and milk products, were the primary dietary iodine source (55%). Iodine intake estimated from 24-h UIE and 24-h dietary recall was moderately correlated (Spearman rank correlation coefficient r = 0.34, p < 0.05). The average iodine concentration in household salt was 14 mg I/kg, with 45% of the samples below the minimum threshold preconized by WHO (15 mg I/kg). The contribution of discretionary salt to the daily iodine intake was around 38%.

CONCLUSION

This study contributes new knowledge about iodine status in Portuguese working adults. The results revealed moderate iodine deficiency, particularly in women. Public health strategies and monitoring programs are needed to ensure iodine adequacy in all population groups.

Home blood pressure-lowering effect of digital therapeutics in hypertension: impact of body weight and salt intake

Lifestyle modifications, including body weight reduction and salt restriction, help reduce blood pressure (BP). This study investigated the effects of body mass index (BMI) and salt intake on home BP reductions in unmedicated patients with hypertension receiving guideline-based lifestyle modification from doctors (control group) or with the addition of a digital therapeutics intervention. Data from the HERB Digital Hypertension 1 (HERB-DH1) pivotal trial were analyzed. Home BP was measured for 7 days before each study visit (baseline, and 4/8/12 weeks). Body weight was measured at each visit and salt intake questionnaire was answered at baseline and 12 weeks. This analysis included 302 patients with sufficient home BP monitoring data (digital therapeutics: 156; control group: 146). The reduction in morning home SBP from baseline to 12 weeks was significantly greater in the digital therapeutics vs. control group for patients with baseline BMI ≥ 25 kg/m² and higher salt intake group (self-reported salt intake score ≥ 14) (-5.1 mmHg, p < 0.01). Patients in the digital therapeutics group who experienced a reduction in BMI and an improvement in salt intake score during the 12-week study also had a significantly greater reduction in morning home SBP compared with patients in the control group (-7.2 mmHg, p < 0.01). The digital therapeutic intervention reduced home BP the most in unmedicated patients with hypertension with high baseline BMI and salt intake score. Those with improvements in both BMI and salt intake during the digital therapeutics intervention achieved the greatest reduction in home BP vs. control.Clinical trial registration: Japan Registry of Clinical Trials (jRCT2032190148).

Importance of dietary salt restriction for patients with primary aldosteronism during treatment with mineralocorticoid receptor antagonists: The potential importance of post-treatment plasma renin levels

We measured dietary salt intake in 26 patients with primary aldosteronism treated with mineralocorticoid receptor antagonists and evaluated whether plasma renin levels were affected by dietary salt intake pre-treatment and post 6 months of mineralocorticoid receptor antagonist treatment. The dietary salt intake level was calculated using spot urine sodium and creatinine concentrations, body weight, height, and age. The clinical parameters pre- and post- treatment were compared. The systolic and diastolic blood pressure levels decreased, and the serum potassium and active renin concentration increased significantly. Although the dietary salt intake did not change after treatment, the differences in dietary salt intake and active renin concentration pre- and post- treatment were inversely correlated (r = -0.418, p = 0.03). The 26 patients were divided into two groups with active renin concentration levels ≥5 pg/mL (Group 1) and <5 pg/mL (Group 2) after treatment. The Group parameters did not differ pre- and post- treatment. Group 1 evidenced improvements in systolic and diastolic blood pressures, and the potassium level and active renin concentration over time; Group 2 did not. Group 1 evidenced no significant correlation between the differences in dietary salt intake and active renin concentration levels (r = -0.481, p = 0.11) but Group 2 showed a strong inverse correlation (r = -0.7599, p = 0.01). In conclusion, we found that an active renin concentration level <5 pg/mL post-mineralocorticoid receptor antagonist treatment may indicate that salt sensitivity has not adequately improved, emphasizing the importance of measuring plasma renin levels after such treatment.

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.

Dietary sodium intake remains high in Brazil: Data from the Brazilian National Dietary Surveys, 2008-2009 and 2017-2018

Reducing salt intake is considered one of the most cost-effective interventions to decrease morbidity and mortality resulting from noncommunicable diseases. This study aimed to describe changes in sodium intake in the Brazilian population using data from the National Dietary Surveys (NDS) conducted in 2008-2009 and 2017-2018. We hypothesized that over the 10-year period evaluated, sodium intake has remained high in Brazil. Nationwide representative samples of 34,003 and 46,164 individuals (aged ≥10 years) from NDS 2008-2009 and 2017-2018, respectively, were evaluated. Food consumption data were obtained from 2 nonconsecutive food records (NDS 2008-2009) and two 24-hour food recalls (NDS 2017-2018). Trends, percentiles of distribution, and proportions of the population exceeding the age-specific tolerable upper intake level for sodium were estimated. Dietary sodium intake was also estimated as a function of energy intake (mg/1000 kcal). Overall, mean crude daily sodium intake was slightly lower in 2017-2018 than in 2008-2009 (2489 mg/d vs. 2529 mg/d). The decrease in sodium intake (mg/day) was statistically significant (P < .05) only among female adolescents and subjects in the highest income level. Additionally, an overall statistically significant increase in dietary sodium density was observed independent of age, sex, and income level for energy-adjusted data (P < .05). Our findings indicate that sodium intake has not significantly changed over time in the Brazilian population; thus, policies aimed at reducing sodium intake in Brazil are necessary.

Adding salt to foods and hazard of premature mortality

AIMS

We analyzed whether the frequency of adding salt to foods was associated with the hazard of premature mortality and life expectancy.

METHODS AND RESULTS

A total of 501 379 participants from UK biobank who completed the questionnaire on the frequency of adding salt to foods at baseline. The information on the frequency of adding salt to foods (do not include salt used in cooking) was collected through a touch-screen questionnaire at baseline. We found graded relationships between higher frequency of adding salt to foods and higher concentrations of spot urinary sodium or estimated 24-h sodium excretion. During a median of 9.0 years of follow-up, 18 474 premature deaths were documented. The multivariable hazard ratios [95% confidence interval (CI)] of all-cause premature mortality across the increasing frequency of adding salt to foods were 1.00 (reference), 1.02 (0.99, 1.06), 1.07 (1.02, 1.11), and 1.28 (1.20, 1.35) (P-trend < 0.001). We found that intakes of fruits and vegetables significantly modified the associations between the frequency of adding salt to foods and all-cause premature mortality, which were more pronounced in participants with low intakes than those with high intakes of these foods (P-interaction = 0.02). In addition, compared with the never/rarely group, always adding salt to foods was related to 1.50 (95% CI, 0.72-2.30) and 2.28 (95% CI, 1.66-2.90) years lower life expectancy at the age of 50 years in women and men, respectively.

CONCLUSIONS

Our findings indicate that higher frequency of adding salt to foods is associated with a higher hazard of all-cause premature mortality and lower life expectancy.

The frequency of early age-related macular degeneration and its relationship with dietary pattern in Hunan, China: a cross-sectional study

PURPOSE

To estimate the frequency of age-related macular degeneration (AMD) among people who underwent health examination in Hunan, China and to determine the relationship between dietary pattern and the risk of AMD.

METHODS

The Questionnaire was used to collect dietary data from 56,775 study participants of ≥ 50 years old who underwent health examination at the Department of Health Management, the Third Xiangya Hospital of Central South University between January 2017 and December 2019. The diagnosis of AMD was based on the results of color fundus photography (CFP), spectral-domain optical coherence tomography (OCT) and multispectral imaging (MSI). After excluding participants with incomplete records or other ocular disease that may affect the results of fundus examination, a total of 43,672 study participants were included. The univariate and multivariate logistic regression analyses were used to determine the relationship between dietary pattern and the frequency of AMD.

RESULTS

Among the 43,672 study participants, 1080 (2.5%) had early AMD: the frequencies were 2.6% (n = 674) in men and 2.3% (n = 406) in women; the frequencies were 1.0% (n = 289), 3.6% (n = 401), 9.1% (n = 390) in 50-59, 60-69, ≥ 70 years old, respectively. And the age-standard frequency was 6.6% over the 60 years old in Hunan China. The high-salt intake increased the risk of early AMD [odds ratio (OR) = 1.61, 95% confidence interval (CI) = 1.54-1.68], whereas the intake of meat decreased the risk (OR = 0.90, 95% CI = 0.81-0.99).

CONCLUSION

In Hunan China, there was a high frequency of early AMD detected through health examination over the 60 years old. And high-salt intake increases the risk of early AMD, whereas intake of meat decreases the risk. Modulating the dietary pattern and reducing the salt intake as an AMD prevention strategy warrant further study.

Impact of salt intake on urinary albumin excretion in patients with type 2 diabetic nephropathy: a retrospective cohort study based on a generalized additive model

Diabetic kidney disease is an important and common cause of end-stage renal disease. Measurement of urinary albumin excretion (UAE) requires the diagnosis of the stage of diabetic nephropathy and the prognosis of renal function. We aimed to analyze the impact of lifestyle modification on UAE in patients with stage 2 and 3 type 2 diabetic nephropathy who received comprehensive medical care, using a generalized additive model (GAM), an explanatory machine learning model. In this retrospective observational study, we used changes in HbA1c, systolic blood pressure (SBP), and diastolic blood pressure (DBP) levels; body mass index (BMI); and daily salt intake as factors contributing to changes in UAE. In total, 269 patients with type 2 diabetic nephropathy were enrolled (stage 2, 217 patients; stage 3, 52 patients). The rankings that contributed to changes in UAE over 6 months by permutation importance were the changes in daily salt intake, HbA1c, SBP, DBP, and BMI. GAM, which predicts the change in UAE, showed that with increase in the changes in salt intake, SBP, and HbA1c, the delta UAE tended to increase. Salt intake was the most contributory factor for the changes in UAE, and daily salt intake was the best lifestyle factor to explain the changes in UAE. Strict control of salt intake may have beneficial effects on improving UAE in patients with stage 2 and 3 diabetic nephropathy.

Excessive dietary salt promotes neuroinflammation to worsen retinopathy in mice with streptozotocin-induced diabetes

OBJECTIVE

Diabetic retinopathy (DR) includes vascular and neural tissue injury. Persistent low-grade inflammation may contribute to DR. Increased salt intake has been shown to promote autoimmunity in the brain. This study determined the role of salt intake in DR development.

METHODS

Eight-week-old C57BL/6 J male mice received streptozotocin to induce diabetes. Diabetic or non-diabetic mice were fed a diet containing normal, low and high amounts of salt. The retinal function, structure and inflammatory response were determined 8 weeks after the establishment of diabetes. Interleukin (IL)-1β or a NLR family pyrin domain containing 3 (NLRP3) inhibitor was injected intravitreally and the retinal changes were evaluated.

RESULTS

A high salt diet worsened the functional and structural damage of retinal cells and increased IL-1β in the retina of diabetic mice. IL-1β injection impaired the function of photoreceptors and retinal structure in the diabetic mice. Blocking NLRP3 inhibited IL-1β increase in the mouse bone marrow macrophages cultured in high sodium medium. NLRP3 inhibition attenuated retinal injury of diabetic mice on high salt diet. A low-salt diet also triggered inflammation and cell damage in the retina of diabetic mice but at a lower grade than those induced by high salt diet. A low or high salt diet for 8 weeks did not induce inflammation or cell injury in the retina of mice without diabetes.

CONCLUSION

These results indicate that high salt intake has deleterious effects in DR development through NLRP3 inflammasome activation and the subsequent production of IL-1β. Limiting salt intake may not attenuate DR development.

Positive relationships between annual changes in salt intake and plasma B-type natriuretic peptide levels in the general population without hypertension and heart diseases

Excessive salt intake causes hypertension and heart diseases. B-type natriuretic peptide (BNP) is a surrogate marker of heart disease, and a slightly elevated BNP level is associated with a poor prognosis. Our previous cross-sectional study demonstrated that plasma BNP has a significant positive association with daily salt intake in the general population. However, the relationship between changes in salt intake and changes in plasma BNP remains unknown. We recruited 3051 participants without hypertension or electrocardiogram abnormalities who underwent annual health check-ups for two consecutive years. Clinical parameters, including plasma BNP, were obtained, and daily salt intake was evaluated using urinary samples. Annual changes in these parameters were calculated. The median plasma BNP level was 12.9 pg/mL, and the daily salt intake was 8.73 ± 1.89 g. The annual changes in plasma BNP and daily salt intake were 4.79 ± 36.38% and 2.01 ± 21.80%, respectively. Participants in the highest quartile of annual changes in daily salt intake showed the largest annual changes in plasma BNP. Annual changes in plasma BNP indicated a significant positive association with daily salt intake. Moreover, multiple linear regression analyses revealed that annual changes in plasma BNP showed a significant positive association with daily salt intake after adjustments. Our study showed a significant positive relationship between annual changes in plasma BNP and annual changes in daily salt intake. The suppression of plasma BNP is therefore induced by salt intake restriction. The monitoring of plasma BNP while reducing salt intake may therefore prevent heart diseases and lead to improved prognoses in the general population without heart diseases.

National and sub-national trends of salt intake in Iranians from 2000 to 2016: a systematic analysis

Background

One fifth of the global burden of cardiovascular diseases (CVDs) in 2017 was attributable to excessive salt intake. As a member of the World Health Organization (WHO), Iran has committed itself to a 30% reduction in salt intake by 2025. Evidence on the amount and trend of salt intake among the Iranian population at national and sub-national levels is scarce. This study aimed to estimate the Iranian population’s salt intake during 2000–2016 at the national and sub-national levels, by sex and age groups.

Methods

Data on national and sub-national mean salt intake was obtained through systematically searching the literature and contacting the research studies’ principal investigators. Data collected through various methods were harmonized using the cross-walk method. Bayesian hierarchical and spatio-temporal-age regression models and simulation analysis were used to estimate the mean salt intake and its uncertainty interval across sex, age, year, and province.

Results

National age-sex standardized mean salt intake decreased from 10·53 g/day (95% uncertainty interval [UI]: 10·2 to 10·9) in 2000 to 9·41 (9·2 to 10·6) in 2016 (percent change: − 9·8% [− 21·1–3·1]). The age-standardized mean salt intake in women had decreased from 9·8 g/day (95% UI: 9·0–10·6) in 2000 to 9·1 g/day (8·6–9·7) in 2016 (percent change: − 6·6% [− 19·0–7·9]). The same measure in men was 11·1 g/day in 2000 (95% UI: 10·3–11·8) and 9·7 g/day (9·1–10·2) in 2016 (percent change: − 12·7% [− 23·0 – -0·9]).

Age-sex standardized mean salt intake at the sub-national level in 2016 varied from 8·0 (95% UI: 7·0–9·0) to 10·5 (10·0–11·1). The difference between the provinces with the highest and the lowest levels of salt intake in 2016 was 31·3%.

Conclusion

Salt intake decreased in Iran from 2000 to 2016, while persistently exceeding the recommended values. This declining trend was more pronounced between 2010 and 2016, which might be attributed to Iran’s compliance to WHO’s Action Plan for reducing NCDs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13690-022-00871-w.

A review of risk factors and prevention strategies for exercise associated hyponatremia

Exercise-associated hyponatremia (EAH) is defined as a serum sodium concentration under 135 mmol·L-1 during or within 24 h of exercise. Increasing interest in endurance events has led to a higher number of athletes presenting with this potentially life-threatening condition. EAH is largely caused by the overconsumption of hypotonic fluids leading to weight gain during exercise. The primary risk factors include the inappropriate secretion of arginine vasopressin, longer exercise duration, smaller body mass, and to smaller extent ingestion of non-steroidal anti-inflammatory drugs. Accurate tracking of fluid intake and losses to prevent weight gain during exercise, sodium supplementation, and heat acclimatization may help attenuate declines in serum sodium concentration during exercise.

Validation and reproducibility of a semi-qualitative food frequency questionnaire for assessment of sodium intake in Iranian population

Background

Few semi-quantitative food frequency questionnaires (SFFQ)s has yet been developed to assess sodium intake in Middle East region. This study was performed to validate a SFFQ for assessment of sodium consumption and food groups΄ contribution to sodium intake.

Methods

This study was performed on 219 healthy participants including 113 adults aged ≥19 years and 106 children aged 6–18 years in Isfahan, Iran. They were administered two SFFQ at the beginning and after 1 year to evaluate the reproducibility. The validity of SFFQ for assessment of sodium intake was compared with 24-h urine sodium and twelve 24-h dietary recalls which were completed monthly during a year as two standard methods.

Results

Correlation coefficient between the contribution of food groups to sodium intake based on SFFQ and 24-h dietary recalls varied from 0.04 for legumes (P = 0.667) to 0.47 for added salt (P < 0.001). There was a significant correlation between the estimated total sodium intake based on SFFQ and both standard methods (P < 0.01). Intraclass correlation coefficient (95% CI) between first and second SFFQ had a diverse range from 0.10 (-0.05, 0.17) for fats and oils to 0.49 (0.28, 0.69) for bread. According to the Bland-Altman plots, we observed an acceptable level of agreement between the two methods for sodium intake.

Conclusions

The SFFQ was a relatively valid and reproducible method for estimating sodium intake. Combination of this SFFQ with a valid prediction of 24-h urinary sodium excretion can be useful in achieving more accurate results.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12937-021-00749-7.

Dietary salt consumption pattern as an antecedent risk factor for hypertension: Status, vision, and future recommendations

Multiple salt reduction strategies have been devised from time to time, addressing the issues of hypertension without considering the other essential factors, like the variability of salt sensitivity from the person to person. In this paper, we discuss how high salt consumption is one modifiable risk factor associated with hypertension among Indians, and there needs to be updated cut-off values. A thorough literature search on salt consumption articles on well-known search engines like Cochrane Library, PubMed, Google Scholar and Embase electronic database revealed a paucity of data in this field for India. Several studies revealed that the mean salt intake among the Indian populations ranges between 5.22 and 42.30 g/day. Moreover, among other risk factors analysed, salt intake (≥ 5 gm/day) was significantly associated with the development of hypertension. Although the need to address reduced salt intake for primordial prevention of hypertension and related cardiovascular diseases (CVDs) in India is well acknowledged by the key stakeholders, social and cultural beliefs, unorganized food retail sector and lack of existing food policing are some of the potential barriers that affect the progress and employment of such effective strategies. Some multinational food companies have already research is warranted to evaluate the contextual barriers and facilitators and to adopt effective strategies to improve awareness among consumers, to encourage the endorsement of salt reduction by the food industry, and to facilitate the adoption of countrywide consumer-friendly food labelling. We concluded that salt consumption is high in India, although this assessment has been done primarily by subjective methods in India. People all across are recommended the same cut-off value of dietary salt consumption regardless of the diversity in dietary patterns and environmental conditions across the country. There is an urgent need to address these issues through evidence-based population research.

Development of a Method for Estimating Dietary Salt Intake Using the Overnight Urinary Sodium/Potassium Ratio

Background

There are many patients who need to restrict and assess salt in their diet. However, it is difficult to estimate daily salt intake accurately and easily. Therefore, a method for estimating dietary salt intake using the overnight urinary sodium (Na)/potassium (K) ratio was developed.

Methods

The study involved 43 healthy adults (13 males, 30 females). From 2018 to 2020, subjects consumed a salt-adjusted diet for 11 - 30 days continuously, and overnight urine was collected daily. Using the previous day's salt intake as the objective variable, an equation for estimating the salt intake was developed using a general linear model. To verify the accuracy of the estimating equation, the estimated salt intake of the previous day was calculated using our equation and Tanaka's equation, which is an estimating equation from spot urine widely used in clinical practice and epidemiological studies to estimate dietary salt intake, and they were compared with the actual salt intake.

Results

The results of the analysis showed that model 1 (previous day's salt intake (g) = 3.62 + 0.64 × urinary Na/K ratio + 0.18 × conductivity (mS/cm) - 0.43 × sex (male 0, female 1)) was the optimal model. Then, salt intake was estimated using model 1 and Tanaka's equation, and compared with actual salt intake. The Pearson's product-moment correlation coefficient between the actual and estimated salt intake was r = 0.618 (P < 0.001) and r = 0.573 (P < 0.001) for model 1 estimates and Tanaka's equation estimates, respectively. The percentages of errors within ±30% from the actual salt intake were 64.2% and 58.4% for model 1 and Tanaka's equation, respectively.

Conclusion

An equation for estimating salt intake was developed using the Na/K ratio and conductivity of overnight urine. Although the applicability of this method to hypertensive patients and the elderly has not been studied and needs to be clarified in the future, the estimating equation developed is simple and may be a useful method for daily monitoring of dietary salt intake.

Salt reduction to prevent hypertension: the reasons of the controversy

There is a causal relationship between dietary salt intake and blood pressure. A reduction in salt intake from the current world average of ∼10 g/day to the WHO recommended level of <5 g/day, lowers blood pressure and reduces the risk of cardiovascular disease and all-cause mortality. However, a few cohort studies have claimed that there is a J-shaped relationship between salt intake and cardiovascular risk, i.e. both high and low salt intakes are associated with an increased risk. These cohort studies have several methodological problems, including reverse causality, and inaccurate and biased estimation of salt intake, e.g. from a single spot urine sample with formulas. Recent studies have shown that the formulas used to estimate salt intake from spot urine cause a spurious J-curve. Research with inappropriate methodology should not be used to refute the robust evidence on the enormous benefits of population-wide reduction in salt intake. Several countries, e.g. Finland, the UK, have successfully reduced salt intake, which has resulted in falls in population blood pressure and deaths from stroke and ischaemic heart disease. Every country should develop and implement a coherent, workable strategy to reduce salt intake. Even a modest reduction in salt intake across the whole population will lead to a major improvement in public health, along with huge cost-savings to the healthcare service.

The Complex Role of Cognitive and Behavioral Factors in Salt Intake Levels of Women

Background

High salt intake is responsible for some serious health consequences. This study aims to investigate the interrelationship between salt intake cognitive and behavioral factors and urinary sodium excretion levels in women.

Methods

A descriptive analytical cross-sectional study was conducted in two residential complexes in Ahvaz city, Iran. 260 female participants were selected using systematic random sampling. Data on salt-related cognitive factors, including knowledge, perceived susceptibility, perceived severity, attitude, intention, self-efficacy, and behavior, were collected using a validated questionnaire. To determine true salt intake, 24-hour urinary sodium excretion level was measured. Data was analyzed using Pearson correlation, one-way Anova, and linear regression tests.

Results

81.2% of the participants’ salt intake was higher than the WHO recommended value (5 grams/day). A significant relationship between sodium excretion level and knowledge (r = –0.332, p < 0.001), attitude (r = –0.144, p = 0.02), behavior (r = –0.130, p = 0.036), and perceived severity (r = –0.135, p = 0.03) was found. An R² of 0.134 demonstrates a 13.4% variation in urinary sodium excretion, associated with knowledge and perceived severity.

Conclusion

Future interventions should aim to improve all the salt-related cognitive factors with placing an emphasis on increasing salt-related knowledge and perceived severity.

Relationship between salt intake and sleep disordered breathing in dialysis patients

BACKGROUND

The prevalence of sleep disordered breathing is high in patients with end-stage renal disease. Salt intake is related to the severity of obstructive sleep apnea in patients with resistant hypertension and hyperaldosteronism. We investigated the relationship between salt intake and sleep disordered breathing in patients on maintenance hemodialysis.

PATIENTS AND METHODS

We studied 128 dialysis outpatients (mean age 63 ± 11 years) who were followed at Kokura Daiichi Hospital. We estimated each patient's salt intake using an InBody S10 body composition analyzer and measured the 3% oxygen desaturation index (ODI) during sleep using a Pulsewatch: PMP-200 GplusX.

RESULTS

The average estimated salt intake was 8.0 ± 2.6 g/day, and the median value of that was 7.5 g/day. Blood pressure (BP) before and after dialysis were 140 ± 18/78 ± 11 and 127 ± 13/72 ± 8 mmHg, respectively. The geometric average number of 3% ODI was 7.1, and sleep disordered breathing was detected in 30% of all subjects. The patients with ≥ 7.5 g/day salt intake were younger and more frequently male and had higher body mass index (BMI) and BP before dialysis compared to those with salt intakes < 7.5 g/day. Patients with ≥ 7.5 g/day salt intake had a significantly higher geometric average number of 3% ODI; however, this relationship became weaker after adjusting for BMI. The same relationship was obtained for the prevalence of sleep disordered breathing.

CONCLUSION

The prevalence of sleep disordered breathing in patients on maintenance hemodialysis was high, and the sleep disordered breathing was associated with salt intake and BMI.

Strengthening Knowledge to Practice on Effective Salt Reduction Interventions in Low- and Middle-Income Countries

PURPOSE OF REVIEW

The objective of this review was to consolidate available published information on the implementation and evaluation of salt reduction interventions in low- and middle-income countries (LMICs).

RECENT FINDINGS

The Science of Salt database (made up of studies identified in a weekly Medline search) was used to retrieve articles related to the implementation of salt reduction interventions from June 2013 to February 2020. Studies that measured the effects of the interventions in LMICs, based on four outcome measures-salt intake; sodium levels in foods; knowledge, attitudes, and behaviours (KABs) towards salt; and blood pressure-were included. Results were summarised overall and according to subgroups of intervention type, duration, sample size, country's income class, and regional classification. The review identified 32 studies, representing 13 upper middle-income and four lower middle-income countries. The main salt reduction interventions were education, food reformulation, and salt substitution; and many interventions were multi-faceted. More studies reported a positive effect of the interventions (decreased salt intake (12/17); lower sodium levels in foods or compliance with agreed targets (6/6); improved KAB (17/19); and decreased blood pressure (10/14)) than a null effect, and no study reported a negative effect of the intervention. However, many studies were of small scale and targeted specific groups, and none was from low-income countries. Consumer education, food reformulation, and salt substitution, either alone or in combination, were effective in their target populations. Supporting scale-up of salt reduction interventions in LMICs is essential to cover broader populations and to increase their public health impact.

Salt intake was higher among males and those with high BMI and waist circumference: introduction to the Malaysian Community Salt Survey (MyCoSS), a population-based salt intake survey in Malaysia

BACKGROUND

Recognising that excessive dietary salt intake is associated with high blood pressure and adverse cardiovascular health, the Ministry of Health Malaysia conducted the Malaysian Community Salt Survey (MyCoSS) among Malaysian adults. This paper introduced MyCoSS projects and presented findings on the salt intake of the Malaysian adult population.

METHODS

MyCoSS was a nationally representative survey, designed to provide valuable data on dietary salt intake, sources of salt in the diet, and knowledge, perception, and practice about salt among Malaysian adults. It was a cross-sectional household survey, covering Malaysian citizens of 18 years old and above. Multi-stage-stratified sampling was used to warrant national representativeness. Sample size was calculated on all objectives studied, and the biggest sample size was derived from the knowledge on the effect of high salt on health (1300 participants). Salt intake was estimated using a single 24-h urine collection and its sources from a food frequency questionnaire. Knowledge, attitude, and practice were determined from a pre-tested questionnaire. All questionnaires were fully administered by trained interviewers using mobile devices. Anthropometric indices (weight, height, and waist circumference) and blood pressure were measured using a standardised protocol. Ethical approvals were obtained from the Medical Research Ethics Committee, Ministry of Health Malaysia, and Queen Mary University of London prior to conducting the survey.

RESULTS

Findings showed that the average sodium intake of Malaysian adults (3167 mg/day) was higher than the WHO recommendation of 2000 mg/day. Daily intake was significantly higher among males and individuals with higher BMI and higher waist circumference.

CONCLUSION

Salt intake in the Malaysian population was higher than the WHO recommendation. MyCoSS's findings will be used for the development and implementation of national salt reduction policy. A successful implementation of a national salt reduction programme in Malaysia will benefit the whole population.

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.

Salt intake and blood pressure in Iranian children and adolescents: a population-based study

BACKGROUND

Previous studies have reported a high prevalence of hypertension in Iranian students, especially in rural areas. The aim of this study was to investigate the daily intake of salt in students and its association with high blood pressure.

METHODS

A random sub-sample was selected from the participants of the second phase of Shahroud schoolchildren eye cohort study and then a random urine sample was tested for sodium, potassium and creatinine. Urine electrolyte esexcretion and daily salt intake were calculated by Tanaka et al.'s formula.

RESULTS

Among 1455 participants (including 230 participants from rural area and 472 girls), the mean age was 12.9 ± 1.7 year and the mean daily salt intake was 9.7 ± 2.6 g (95% CI 9.5-9.8). The mean salt consumption in rural areas [10.8 (95% CI 10.4-11.2)] was higher than urban areas [9.4 (95% CI 9.3-9.6)], in people with hypertension [10.8 (95% CI 10.3-11.3)] was more than people with normal blood pressure [9.4 (95% CI 9.3-9.6)], and in boys [9.8 (95% CI 9.7-10.0)] was more than girls [9.3 (95% CI 9.1-9.6)]. Higher age, BMI z-score, male sex and rural life, were associated with increased daily salt intake. Increased salt intake was associated with increased systolic and diastolic blood pressure.

CONCLUSION

Daily salt intake in Iranian adolescents was about 2 times the recommended amount of the World Health Organization, was higher in rural areas and was associated with blood pressure. Reducing salt intake should be considered as an important intervention, especially in rural areas.

Estimation of salt intake assessed by 24-h urinary sodium level among adults speaking different dialects from the Chaoshan region of southern China

OBJECTIVE

Dietary salt intake may vary depending on different lifestyles. We aimed to estimate the different salt intakes and evaluate the knowledge and self-awareness about salt among people speaking the Teochew, Teochew-Hakka and Hakka dialects in the Chaoshan region of southern China.

DESIGN

The study followed a cluster sampling of residents in Chaoshan region. General characteristics, lifestyles, health status as well as knowledge and self-awareness related to salt intake were investigated using a questionnaire. Anthropometric variables as well as Na and K excretion in a 24-h urine collection were measured.

SETTING

Chaoshan region of China.

PARTICIPANTS

Four hundred fifteen adults who spoke only one of these three dialects.

RESULTS

The salt intake of adults who spoke the Teochew, Teochew-Hakka and Hakka dialects was 7·19 (interquartile range (IQR) 5·29-10·17), 9·03 (IQR 6·62-11·54) and 10·12 (IQR 7·61-12·82) g/d, respectively, with significant differences between Teochew and Teochew-Hakka speakers and between Teochew and Hakka speakers (both P < 0·05). The Na:K ratio for adults who spoke the three dialects was 3·00 (IQR 2·00-4·11), 3·50 (IQR 2·64-4·82) and 4·52 (IQR 3·35-5·97), respectively, and differed significantly among the groups (all P < 0·05). Multiple linear regression analysis showed increased Na:K ratio associated with hypertension (β = 0·71, P = 0·043) in Hakka speakers. Knowledge and self-awareness about salt intake were poor in this population.

CONCLUSIONS

Salt intake was closely related to lifestyles and was higher than the upper limit (5 g/d) recommended by the WHO in adults of Chaoshan, especially those speaking the Hakka dialect.

Change in mean salt intake over time using 24-h urine versus overnight and spot urine samples: a systematic review and meta-analysis

Background

Little is known about the capacity of overnight and spot urine samples to estimate changes in mean salt intake over time. The objective of this review was to compare the estimates of change in mean population salt intake based on 24-h urine and overnight/spot urine samples.

Methods

Studies were systematically identified through searches of peer-reviewed databases (Medline, Embase, Global Health, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews) and grey literature. Studies that reported estimates of mean salt intake for at least two time points based on both 24-h and overnight/spot urines were deemed eligible. The capacity of overnight/spot urine samples to estimate the change in mean salt intake was assessed both at the individual-study level and overall through random-effects meta-analyses. The level of heterogeneity was assessed through the I² statistic. Subgroup and sensitivity analyses were conducted to explore possible sources of heterogeneity, and check the robustness of the findings from the primary analysis.

Results

A total of 1244 records were identified, 50 were assessed as full text, and 14 studies met the criteria, capturing data on 7291 participants from seven countries. Nine and five studies collected overnight and spot urines, respectively. The comparison of the change in mean salt intake between 24-h and overnight/spot urines showed some inconsistencies at the individual study-level. The pooled mean change in salt intake was − 0.43 g/day (95% CI − 1.16 to 0.30; I² = 95%) using 24-h urines, and − 0.22 g/day (− 0.65 to 0.20; I² = 87%) using overnight/spot urines, with a pooled difference-in-differences between the two methods of 0.27 g/day (− 0.23 to 0.77; I² = 89%). Subgroup analyses showed substantial heterogeneity for most subgroups. Sensitivity analyses did not change the effect observed in the primary analysis.

Conclusion

The evidence for the capacity of overnight/spot urines to estimate changes in mean salt intake over time is uncertain. More research where overnight/spot urines are collected in parallel with 24-h urines is needed to enable a more in-depth evaluation of these alternative approaches to estimating change in mean salt intake.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12937-020-00651-8.

Salt-reduction strategies may compromise salt iodization programs: Learnings from South Africa and Ghana

OBJECTIVES

Universal salt iodization has been adopted by many countries to address iodine deficiency. More recently, salt-reduction strategies have been widely implemented to meet global salt intake targets of <5 g/d. Compatibility of the two policies has yet to be demonstrated. This study compares urinary iodine excretion (UIE) according to 24-h urinary sodium excretion, between South Africa (SA) and Ghana; both countries have implemented universal salt iodization, but in Ghana no salt-reduction legislation has been implemented.

METHODS

Participants from the World Health Organization's Study on Global Ageing and Adult Health Wave 3, with survey and valid 24-h urinary data (Ghana, n = 495; SA, n = 707), comprised the sample. Median 24-h UIE was compared across salt intake categories of <5, 5-9 and >9 g/d.

RESULTS

In Ghana, median sodium excretion indicated a salt intake of 10.7 g/d (interquartile range [IQR] = 7.6), and median UIE was 182.4 µg/L (IQR = 162.5). In SA, both values were lower: median salt = 5.6 g/d (IQR = 5.0), median UIE = 100.2 µg/L (IQR = 129.6). UIE differed significantly across salt intake categories (P < 0.001) in both countries, with positive correlations observed in both-Ghana: r = 0.1501, P < 0.0011; South Africa: r = 0.4050, P < 0.0001. Participants with salt intakes <9 g/d in SA did not meet the World Health Organization's recommended iodine intake of 150 µg/d, but this was not the case in Ghana.

CONCLUSIONS

Monitoring and surveillance of iodine status is recommended in countries that have introduced salt-reduction strategies, in order to prevent reemergence of iodine deficiency.

The association between dietary sodium intake, adiposity and sugar-sweetened beverages in children and adults: a systematic review and meta-analysis

Higher intakes of Na may contribute to weight gain. The primary aim of this systematic review and meta-analysis was to examine the relationship between dietary Na intake and measures of adiposity in children and adults. Given the previous link between Na intake and the consumption of sugar-sweetened beverages (SSB), which are a known risk factor for obesity, a secondary aim examining the relationship between Na intake and SSB consumption was assessed. A systematic literature search identified cross-sectional and longitudinal studies and randomised controlled trials (RCT) which reduced dietary Na (≥3 months). Meta-analysis was performed for outcomes with ≥3 studies. Cross-sectionally higher Na intakes were associated with overweight/obesity in adults (five studies; n 11 067; OR 1·74; 95 % CI 1·43, 2·13) and in children (three studies; n 3625, OR 3·29; 95 % CI 2·25, 4·80), and abdominal obesity (five studies; n 19 744; OR 2·04; 95 % CI 1·72, 2·42) in adults. Overall, associations remained in sensitivity analyses which adjusted for energy. Findings from longitudinal studies were inconsistent. RCT in adults indicated a trend for lower body weight on reduced-Na compared with control diets (fifteen studies; n 5274; -0·29 kg; 95 % CI -0·59, 0·01; P = 0·06); however, it is unclear if energy intakes were also altered on reduced-Na diets. Among children higher Na intakes were associated with higher intake of SSB (four studies, n 10 329, b = 22, 16 and 26 g/d); no studies were retrieved for adults. Overall, there was a lack of high-quality studies retrieved. While cross-sectional evidence indicates Na intake was positively associated with adiposity, these findings have not been clearly confirmed by longitudinal studies or RCT.

Salt and potassium intake among adult Ghanaians: WHO-SAGE Ghana Wave 3

Though Ghana has high hypertension prevalence, the country lacks current national salt consumption data required to build and enhance advocacy for salt reduction. We explored the characteristics of a randomly selected sub sample that had valid urine collection, along with matched survey, anthropometric and BP data (n = 839, mean age = 60y), from the World Health Organization's Study on global AGEing and adult health (WHO-SAGE), Ghana Wave 3, n = 3053). We also investigated the relationship between salt intake and blood pressure (BP) among the cohort. BP was measured in triplicate and 24 h urine was collected for the determination of urinary sodium (Na), potassium (K), creatinine (Cr) and iodine levels. Hypertension prevalence was 44.3%. Median salt intake was 8.3 g/day, higher in women compared to men (8.6, interquartile range (IQR) 7.5 g/day vs 7.5, IQR 7.4 g/day, p <  0.01), younger participants (18-49 y) compared to older ones (50+ y) (9.7, IQR 7.9 g/day vs 8.1, IQR 7.1 g/day, p <  0.01) and those with higher Body Mass Index (BMI) (> 30 kg/m2) compared to a healthy BMI (18.5-24.9 kg/m2) (10.04, IQR 5.1 g/day vs 6.2, IQR 5.6 g/day, p <  0.01). More than three quarters (77%, n = 647) of participants had salt intakes above the WHO maximum recommendation of 5 g/d, and nearly two thirds (65%, n = 548) had daily K intakes below the recommended level of 90 mmol. Dietary sodium to potassium (Na: K) ratios above 2 mmol/mmol were positively associated with increasing BP with age. Population-based interventions to reduce salt intake and increase K consumption are needed.

Forecasting disability-adjusted life years for chronic diseases: reference and alternative scenarios of salt intake for 2017-2040 in Japan

BACKGROUND

In Japan, a high-sodium diet is the most important dietary risk factor and is known to cause a range of health problems. This study aimed to forecast Japan's disability-adjusted life year (DALYs) for chronic diseases that would be associated with high-sodium diet in different future scenarios of salt intake. We modelled DALY forecast and alternative future scenarios of salt intake for cardiovascular diseases (CVDs), chronic kidney diseases (CKDs), and stomach cancer (SC) from 2017 to 2040.

METHODS

We developed a three-component model of disease-specific DALYs: a component on the changes in major behavioural and metabolic risk predictors including salt intake; a component on the income per person, educational attainment, and total fertility rate under 25 years; and an autoregressive integrated moving average model to capture the unexplained component correlated over time. Data on risk predictors were obtained from Japan's National Health and Nutrition Surveys and from the Global Burden of Disease Study 2017. To generate a reference forecast of disease-specific DALY rates for 2017-2040, we modelled the three diseases using the data for 1990-2016. Additionally, we generated better, moderate, and worse scenarios to evaluate the impact of change in salt intake on the DALY rate for the diseases.

RESULTS

In our reference forecast, the DALY rates across all ages were predicted to be stable for CVDs, continuously increasing for CKDs, and continuously decreasing for SC. Meanwhile, the age group-specific DALY rates for these three diseases were forecasted to decrease, with some exceptions. Except for the ≥70 age group, there were remarkable differences in DALY rates between scenarios, with the best scenario having the lowest DALY rates in 2040 for SC. This represents a wide scope of future trajectories by 2040 with a potential for tremendous decrease in SC burden.

CONCLUSIONS

The gap between scenarios provides some quantification of the range of policy impacts on future trajectories of salt intake. Even though we do not yet know the policy mix used to achieve these scenarios, the result that there can be differences between scenarios means that policies today can have a significant impact on the future DALYs.

Frequency of alcohol drinking modifies the association between salt intake and albuminuria: a 1-year observational study

Albuminuria is an important risk factor for end-stage kidney disease and cardiovascular mortality. This 1-year observational study aimed to assess the effect modification of alcohol drinking on the association between salt intake and albuminuria. Overall, 448 employees at a pharmaceutical company in Japan who underwent annual health checkups in both 2017 and 2018 were evaluated. The main exposure of interest was drinking frequency at their first checkups categorized as rarely, occasionally, and daily. To assess the association between the changes in salt intake and albuminuria, the differences in salt intake estimated from single-spot urine specimens and the urinary albumin-to-creatinine ratio (UACR) between 2017 and 2018 were calculated for each subject. A multivariable-adjusted linear regression model showed a significant association between ∆salt intake and ∆Log UACR (per 1 g/day of ∆salt intake, adjusted ß 0.16 [95% confidence interval 0.14, 0.19]) and an effect modification between drinking frequency and ∆salt intake (P for interaction = 0.088). The association between ∆salt intake and ∆Log UACR was enhanced by drinking frequency in a dose-dependent manner (per 1 g/day of ∆salt intake, adjusted ß 0.13 [0.06, 0.19], 0.16 [0.12, 0.20], and 0.20 [0.13, 0.27] in rare, occasional, and daily drinkers, respectively). In conclusion, the results of the present study indicated that salt-induced albuminuria was enhanced in subjects with higher drinking frequency, suggesting that salt restriction may have a stronger renoprotective effect in subjects with higher drinking frequency.

The FGF-21 genetic variants rs838133 and rs838145 are associated with high salt intake in the Emirati population

Food predilection is linked to variants in the hepatokine "Fibroblast Growth Factor-21" gene (FGF21); with rs838133 linked to the sweet tooth in Caucasians. The effect of FGF21 variants on food intake is still unclear in other populations. A cohort of 196 healthy Emirati subjects was investigated [age: 30.34 ± 9.75yrs (44.4% males)]. The FGF21 rs838133 and rs838145 were genotyped. The daily intake was calculated based on a 61-item food frequency questionnaire. Multivariate analysis was performed using in house R script that implements two-way unsupervised hierarchical clustering to detect the association of the studied single-nucleotide polymorphisms (SNPs) and related SNPs in linkage disequilibrium, using data from the 1000 genome project. Both SNPs were in Hardy-Weinberg Equilaribium (HWE). BMI positively correlated with age (p = 0.002), but not with caloric intake. Salt intake was significantly higher in subjects homozygous (A: rs838133) and (G:rs838145),(p = 0.03 and 0.01, respectively). An interaction was observed between both SNPs; significantly associated with high salt intake. Using publicly available data, both SNPs fall within a region transmitted in Iberians which has a profile closely similar to Caucasians, but far from Chinese population. In conclusion, the minor alleles of FGF21 rs838145 and rs838133 are associated with high salt intake in Emiratis and may suggest neuro-metabolic link to dietary preference across different populations.

Salt need needs investigation

Expensive and extensive studies on the epidemiology of excessive Na intake and its pathology have been conducted over four decades. The resultant consensus that dietary Na is toxic, as well as the contention that it is less so, ignores the root cause of the attractiveness of salted food. The extant hypotheses are that most Na is infiltrated into our bodies via heavily salted industrialised food without our knowledge and that mere exposure early in life determines lifelong intake. However, these hypotheses are poorly evidenced and are meagre explanations for the comparable salt intake of people worldwide despite their markedly different diets. The love of salt begins at birth for some, vacillates in infancy, climaxes during adolescent growth, settles into separate patterns for men and women in adulthood and, with age, fades for some and persists for others. Salt adds flavour to food. It sustains and protects humans in exertion, may modulate their mood and contributes to their ailments. It may have as yet unknown benefits that may promote its delectability, and it generates controversy. An understanding of the predilection for salt should allow a more evidence-based and effective reduction of the health risks associated with Na surfeit and deficiency. The purpose of this brief review is to show the need for research into the determinants of salt intake by summarising the little we know.

Association between dietary sodium intake and non-alcoholic fatty liver disease in the US population

OBJECTIVE

To explore the association between dietary Na intake and non-alcoholic fatty liver disease (NAFLD) in a nationally representative sample of the US population.

DESIGN

In this cross-sectional study, the associations between Na intake and NAFLD, defined by the hepatic steatosis index (HSI) and the fatty liver index (FLI), were assessed through multivariable logistic regression models.

SETTING

Communities in the USA from 2007 to 2014.

PARTICIPANTS

Men and women aged 20 years and older.

RESULTS

A total of 11 022 participants were included in the HSI-defined NAFLD analysis, and a subsample of 5320 participants was included in the FLI-defined NAFLD analysis. Compared with the lowest quartile of Na intake, the highest quartile had a multivariate-adjusted OR and 95 % CI of 1·46 (1·29, 1·65) for NAFLD as defined by HSI, and 1·41 (1·18, 1·69) for NAFLD as defined by FLI. This association was, to some degree, attenuated but remained significant after adjusting for several related metabolic parameters, including BMI, hypertension, hypercholesterolaemia, and diabetes.

CONCLUSIONS

Findings from the current study indicate that dietary Na intake is positively associated with NAFLD in US adults.

High-salt intake increases TRPC3 expression and enhances TRPC3-mediated calcium influx and systolic blood pressure in hypertensive patients

Enhanced transient receptor potential canonical subtype 3 (TRPC3) expression and TRPC3-mediated calcium influx in monocytes from hypertensive rats and patients are associated with increased blood pressure. Daily salt intake is closely related to hypertension, but the relationship between TRPC3 expression and salt intake has not yet been evaluated in hypertensive patients. Using reverse transcription-polymerase chain reaction, we studied the expression of TRPC3 and TRPC3-related store-operated calcium entry (SOCE) in peripheral blood mononuclear cells (PBMCs) from hypertensive and normotensive control subjects. Measurement of SOCE was performed using the fluorescent dye Fura-2 AM. Participants were divided into a low-salt group (<9 g) and a high-salt group (≥9 g) based on 24-h urinary sodium excretion. Increased TRPC3 mRNA expression levels and SOCE were observed in THP-1 cells after high-NaCl treatment. However, administration of the TRPC3-specific inhibitor Pyr3 significantly decreased the effect. Furthermore, the TRPC3 mRNA expression levels in PBMCs from high-salt intake patients with essential hypertension were significantly higher than those in low-salt intake patients compared with those in normotensive control subjects. We also observed significantly increased TRPC3-mediated SOCE in PBMCs from hypertensive subjects (but not from normotensive control subjects), with calcium concentration correlating with salt intake. More importantly, TRPC3 mRNA levels showed a significant correlation with salt intake and systolic blood pressure in patients with essential hypertension. This study demonstrated, for the first time, that increased TRPC3 mRNA levels are associated with elevated salt intake and systolic blood pressure in hypertensive patients.

Salt consumption and the risk of chronic diseases among Chinese adults in Ningbo city

Background

Chronic diseases have become one of essential public health concerns, leading causes of mortality in China. It is related to the changes in dietary pattern and dietary behavior. The objectives are to assess daily salt intake in Chinese people living in Ningbo and to examine its relationship with health outcomes.

Methods

Our study used data from health and nutrition survey in 2017. This study included 2811 adults aged 18–79 years (48% males) from urban and rural areas in Ningbo. A food frequency questionnaire together with demographic, physical and medical questionnaires was used to collect dietary intake, demographic, lifestyle and medical information. Ordinal logistic regression was used in the statistical analysis.

Results

The mean daily salt intake (13.0 g/day) of the participants was higher than the Chinese dietary reference intake (DRI, 6 g/d), which was related to higher risk of pre-hypertension and hypertension. Stratified by gender, education and lifestyle factors, daily salt intake was only significant in the blood pressure category (male: P = 0.048; less education: P = 0.003; urban: P = 0.006; no regular physical activity: P = 0.005, no regular smoking: P = 0.006). Ordinal logistic regression model shows that daily salt intake was significantly associated with higher odds of developing hypertension.

Conclusion

The daily salt intake of the majority of citizens living in Ningbo exceeded Chinese DRI and may increase the risk of hypertension. Moreover, public health intervention of salt restriction is necessarily needed for the prevention and control the ongoing epidemic of chronic diseases.

Food Products That May Cause an Increase in Blood Pressure

PURPOSE OF REVIEW

To review latest reports of the food products which might increase blood pressure and therefore might participate in the pathogenesis of hypertension.

RECENT FINDINGS

Results of clinical study suggest that consumption of high-sodium food leads to transient increase in plasma sodium concentration. This is accompanied by blood pressure increase. Results of both clinical and experimental studies suggest direct vasculotoxic effects of sodium. Increased plasma sodium concentration could mediate its effects on blood pressure by changes in endothelial cell stiffness and glycocalyx integrity. Energy drinks are non-alcoholic beverages with increasing popularity. Clinical, interventional, randomized, placebo controlled, and cross-sectional studies showed that energy drinks may increase arterial blood pressure. Blood pressure increase after exposure for the energy drinks is mainly related to the caffeine content in these drinks. Many case reports were published concerning the clinically significant increase in blood pressure caused by the consumption of liquorice root or food products containing liquorice, such as candies, tea, Pontefract cookies, and chewing gum. Liquorice contains a precursor of glycyrrhetic acid. Glycyrrhetic acid reduces the activity of the 11β-hydroxysteroid dehydrogenase type 2 (11ß-HSD2) isoenzyme, which leads to activation of the mineralocorticoid receptor by cortisol in the distal convoluted tubule resulting in hypertension, hypokalemia, and metabolic alkalosis. The relationship between chronic alcohol intake and blood pressure is well established on the basis of a diverse body of evidence including animal experiments, epidemiological studies, mendelian randomization studies, and interventional studies. Results of recent studies suggested that binge drinking (i.e., episodic consumption of a very high amount of alcohol beverages) has pronounced hypertensinogenic effects. Recently, it was documented that also low doses of alcohol may increase the risk of cardiovascular complications. Therefore, the amount of alcohol consumption that is safe is zero. High-salt food products, energy drinks, food products containing liquorice, and alcoholic beverages have hypertensinogenic properties. Patients with hypertension and other cardiovascular diseases should avoid even accidental consumption of these food products.

The Salt Swap intervention to reduce salt intake in people with high blood pressure: protocol for a feasibility randomised controlled trial

Background

High salt intake is a risk factor for hypertension and cardiovascular disease. Reducing salt intake has been shown to reduce blood pressure. Despite population-level interventions, including product reformulation and public awareness campaigns, adult salt consumption in the UK still exceeds recommendations; this is primarily due to salt consumed in processed and pre-packaged foods. Moderate or high-intensity dietary advice to encourage individuals to reduce their salt intake has been shown to be effective at reducing blood pressure, but evidence of the effectiveness of interventions that are suitable for delivery at scale in routine primary care is scarce. This feasibility trial investigates a complex behavioural change intervention to reduce dietary salt intake and blood pressure by encouraging individuals to purchase lower-salt foods when grocery shopping.

Methods

This randomised controlled trial will test the feasibility of a novel intervention to reduce salt intake, and the trial procedures to assess its effectiveness. We will recruit participants through UK general practices and randomise 40 participants with high blood pressure, in a 2:1 allocation to receive either the Salt Swap intervention or a control information leaflet. The primary outcomes relate to the criteria for progression to a large-scale trial. These include follow-up rates at 6 weeks, fidelity of intervention delivery and use of the intervention mobile app. Secondary outcomes include the effect of the intervention on the salt content of purchased foods (grams per 100 g), urinary sodium excretion assessed through 24-hour urine samples and blood pressure. Trial process measures will be collected and qualitative assessment will provide insights into participant engagement with the intervention content and perceived barriers to and facilitators of salt reduction dietary behavioural change.

Discussion

If the outcomes indicate the trial is feasible and there is evidence that behavioural change may result in salt reduction, we will proceed to a definitive trial to test the effectiveness of the intervention to lower blood pressure. If successful, this intervention approach could be applied not only to people with high blood pressure, but also to the wider population with normal blood pressure in whom dietary salt intake exceeds recommendations.

Trial registration

ISRCTN, 20910962. Registered on 5 April 2017.

Estimating mean population salt intake in Fiji and Samoa using spot urine samples

BACKGROUND

There is an increasing interest in finding less costly and burdensome alternatives to measuring population-level salt intake than 24-h urine collection, such as spot urine samples. However, little is known about their usefulness in developing countries like Fiji and Samoa. The purpose of this study was to evaluate the capacity of spot urine samples to estimate mean population salt intake in Fiji and Samoa.

METHODS

The study involved secondary analyses of urine data from cross-sectional surveys conducted in Fiji and Samoa between 2012 and 2016. Mean salt intake was estimated from spot urine samples using six equations, and compared with the measured salt intake from 24-h urine samples. Differences and agreement between the two methods were examined through paired samples t-test, intraclass correlation coefficient analysis, and Bland-Altman plots and analyses.

RESULTS

A total of 414 participants from Fiji and 725 participants from Samoa were included. Unweighted mean salt intake based on 24-h urine collection was 10.58 g/day (95% CI 9.95 to 11.22) in Fiji and 7.09 g/day (95% CI 6.83 to 7.36) in Samoa. In both samples, the INTERSALT equation with potassium produced the closest salt intake estimate to the 24-h urine (difference of - 0.92 g/day, 95% CI - 1.67 to - 0.18 in the Fiji sample and + 1.53 g/day, 95% CI 1.28 to 1.77 in the Samoa sample). The presence of proportional bias was evident for all equations except for the Kawasaki equation.

CONCLUSION

These data suggest that additional studies where both 24-h urine and spot urine samples are collected are needed to further assess whether methods based on spot urine samples can be confidently used to estimate mean population salt intake in Fiji and Samoa.

Determinants of intention to reduce salt intake and willingness to purchase salt-reduced food products: Evidence from a web survey

To study consumers' intention to reduce their dietary salt intake and willingness to purchase salt-reduced food products, as well as the determinants of these, this research relies on data collected through a web survey of 1030 participants in Denmark. The majority of respondents (66.8%) express no intentions to change their dietary salt intake, but 12.6% indicate such intentions, and 20.6% claim to have already implemented a change. Willingness to purchase salt-reduced food products is high but varies across product categories, ranging from 52% for olives to 72% for meat spreads. Personal and social norms reveal the strongest influences on intention to change dietary habits, whereas personal norms, knowledge, and awareness of health consequences exert the strongest influences on willingness to purchase salt-reduced food products. These results suggest that most consumers are willing to purchase salt-reduced food products, even without having a salt reduction goal. These results are relevant for stakeholders and policy makers, as evidence of how consumers respond to salt-reduced food products and their intention to lower their dietary salt intake.