Dietary Sodium Intake and Mortality

Results of a recent study of data from the National Health and Nutrition Examination Survey (NHANES I) on sodium intake and all-cause and cardiovascular mortality may call into question current recommendations to limit salt intake. Further research is needed to explore the relationship between sodium, cardiovascular disease, and mortality.     

Higher Potassium Intake and Lower Sodium Intake May Help in Reducing CVD Risk by Lowering Salt Sensitivity of Blood Pressure in the Han Chinese Population

Sodium (Na) reduction with a parallel supplemental potassium (K) intake can prevent cardiovascular diseases (CVDs). The relationship of the urinary Na/K ratio and salt sensitivity of blood pressure (SSBP) with CVDs is not clearly explained. We assumed that the SSBP mediates the relationship between the Na/K ratio and CVDs. In total, 2055 subjects who had 24 h urine collected and SSBP determined were included in this study. CVD risk was estimated using the China-PAR equation. MediationMultivariate logistic regression was used to explore the associations between the Na/K ratio or SSBP with CVD risk. Mediation analysis using a logistic regression model was performed. Both the urinary Na/K ratio and SSBP were related to the estimated CVD risk (p < 0.05). The mediation analysis found that SSBP mediated approximately 12% of the association between Na/K ratio and CVD risk. Our findings indicate that higher K intake and lower Na intake may help in preventing CVD risk by reducing SSBP risk in individuals with normotension or stage-one hypertension.     

Urinary Sodium and Potassium Levels and Blood Pressure in Population with High Sodium Intake

The purpose of this study was to examine the association of urinary sodium-to-creatinine ratio and potassium-to-creatinine ratio with blood pressure in a cross-sectional study comprising Korean adults who participated in the Healthy Twin Study. The participants consisted of 2653 men and women in the Healthy Twin Study aged ≥19 years. Participants’ urinary excretion of sodium, potassium, and creatinine was measured from overnight half-day urine samples. Food intake was assessed using a validated food frequency questionnaire. We examined systolic and diastolic blood pressures according to sodium- or potassium-to-creatinine ratios using the generalized linear model. We determined food groups explaining high urinary sodium- or potassium-to-creatinine ratio using the reduced rank regression and calculated sodium- or potassium-contributing food score. We observed that systolic blood pressure was higher among men and women in the highest quintile of urinary sodium-to-creatinine ratio or sodium-to-potassium ratio than it was in the lowest quintile. Geometric means (95% CIs) of the lowest and the highest quintiles of systolic blood pressure (mmHg) were 113.4 (111.8–115.0) and 115.6 (114.1–117.2; P for trend = 0.02), respectively, for sodium-to-creatinine ratio. The association between urinary sodium-to-creatinine and systolic blood pressure was more pronounced among individuals whose body mass index (BMI) was less than 25 kg/m² (P for interaction = 0.03). We found that vegetables, kimchi and seaweed intake contributed to high sodium intake and a sodium-contributing food score were associated with increased blood pressure. In our study, we identified the food groups contributing to high sodium intake and found that high urinary sodium levels were associated with increasing blood pressure among Korean adults.     

北方男性膳食钠摄入量及对钙需要量影响的研究

为研究北方男性膳食钠摄入量及其对尿钙排出量的影响 ,我们对健康男性 1 49人 (老年人 50名、青年人 48名、青少年 51名 )进行 5天称重法膳食调查 ,测定血清中钙、磷、肌、酐 ,2 4h尿中钙、磷、钠、肌酐。结果显示三组膳食钙的摄入量均低于我国供给量。2 4 h尿钠排出量 (即膳食钠摄入量 ) :青少年组 1 43.85mmol/d,青年组 2 53.7mmol/d,老年组 1 84.4mmol/d,三组间差异显著 ( P<0 .0 0 1 )。尿钙排出量与尿钠排出量呈显著正相关 ( P<0 .0 0 1 )。提示北方男性钙的需要量可能受钠的摄入量影响 ,在制定膳食钙供给量标准时应考虑钠的摄入量     

Measuring Population Sodium Intake: A Review of Methods

Reduction of population sodium intake has been identified as a key initiative for reduction of Non-Communicable Disease. Monitoring of population sodium intake must accompany public health initiatives aimed at sodium reduction. A number of different methods for estimating dietary sodium intake are currently in use. Dietary assessment is time consuming and often under-estimates intake due to under-reporting and difficulties quantifying sodium concentration in recipes, and discretionary salt. Twenty-four hour urinary collection (widely considered to be the most accurate method) is also burdensome and is limited by under-collection and lack of suitable methodology to accurately identify incomplete samples. Spot urine sampling has recently been identified as a convenient and affordable alternative, but remains highly controversial as a means of monitoring population intake. Studies suggest that while spot urinary sodium is a poor predictor of 24-h excretion in individuals, it may provide population estimates adequate for monitoring. Further research is needed into the accuracy and suitability of spot urine collection in different populations as a means of monitoring sodium intake.     

Whole Grain Intake and Insulin Sensitivity: Evidence from Observational Studies

Observational studies have found that diets rich in whole-grain foods are associated with improved insulin sensitivity. The improved insulin sensitivity may be mediated in part by magnesium and dietary fiber, two nutrients found in whole-grain foods. By incorporating whole-grain foods into the diet, therefore, insulin sensitivity might be improved .     

2011年高密市居民膳食钠摄入量调查

目的了解高密市居民膳食钠摄入量及来源分布,为制定减盐防控高血压措施提供依据。方法2011年6月18日采用分阶段抽样抽取18～69岁居民,使用24h膳食称重法和调查问卷进行调查,收集膳食钠摄入量及来源分布。结果高密市18～69岁居民人均每日膳食钠摄人量为6065mg,其中来自日常调味品的为5024mg,占82．83％。膳食钠来源前三位的为精盐、其他食品、酱油,分别占膳食钠总量的56．67％、17．11％、16．81％。结论高密市居民膳食钠摄入量超标严重,应采取有效减盐措施。     

Sodium,Potassium and Iodine Intake in an Adult Population of Lithuania

Hypertension is a leading risk factor for cardiovascular events and death. A reduction in salt intake is among the most cost-effective strategies to reduce blood pressure and the risk of cardiovascular diseases. Increasing potassium lowers blood pressure and is associated with lower cardiovascular risk. Adequate iodine intake is important to prevent iodine deficiency disorders. Salt iodization is a key strategy to prevent such deficiency. In Lithuania, no surveys have been performed to directly assess sodium, potassium and iodine consumption. The aim of the present study was to measure sodium, potassium and iodine intake in a randomly selected adult Lithuanian adult population using 24 h urine collections, and to assess knowledge, attitudes and behavior towards salt consumption. Salt and potassium intakes were estimated in 888 randomly selected participants by 24 h urine sodium and potassium excretion and 679 individuals provided suitable 24 h urine samples for the analysis of iodine excretion. Average salt intake was 10.0 (SD 5.3) g/24 h and average potassium intake was 3.3 (SD 1.3) g/24 h. Only 12.5% of participants consumed less than 5 g/24 h of salt. The median value of urinary iodine concentration (UIC) was 95.5 μg/L. Our study showed that average salt intake is twice as high as the maximum level recommended by the World Health Organization while potassium and iodine intakes in Lithuania are below the recommended levels.     

Geospatial Analysis of Sodium and Potassium Intake: A Swiss Population-Based Study

Inadequate sodium and potassium dietary intakes are associated with major, yet preventable, health consequences. Local public health interventions can be facilitated and informed by fine-scale geospatial analyses. In this study, we assess the existence of spatial clustering (i.e., an unusual concentration of individuals with a specific outcome in space) of estimated sodium (Na), potassium (K) intakes, and Na:K ratio in the Bus Santé 1992–2018 annual population-based surveys, including 22,495 participants aged 20–74 years, residing in the canton of Geneva, using the local Moran’s I spatial statistics. We also investigate whether socio-demographic and food environment characteristics are associated with identified spatial clustering, using both global ordinary least squares (OLS) and local geographically weighted regression (GWR) modeling. We identified clear spatial clustering of Na:K ratio, Na, and K intakes. The GWR outperformed the OLS models and revealed spatial variations in the associations between explanatory and outcome variables. Older age, being a woman, higher education, and having a lower access to supermarkets were associated with higher Na:K ratio, while the opposite was seen for having the Swiss nationality. Socio-demographic characteristics explained a major part of the identified clusters. Socio-demographic and food environment characteristics significantly differed between individuals in spatial clusters of high and low Na:K ratio, Na, and K intakes. These findings could guide prioritized place-based interventions tailored to the characteristics of the identified populations.     

Positive and Negative Aspects of Sodium Intake in Dialysis and Non-Dialysis CKD Patients

Sodium intake theoretically has dual effects on both non-dialysis chronic kidney disease (CKD) patients and dialysis patients. One negatively affects mortality by increasing proteinuria and blood pressure. The other positively affects mortality by ameliorating nutritional status through appetite induced by salt intake and the amount of food itself, which is proportional to the amount of salt under the same salty taste. Sodium restriction with enough water intake easily causes hyponatremia in CKD and dialysis patients. Moreover, the balance of these dual effects in dialysis patients is likely different from their balance in non-dialysis CKD patients because dialysis patients lose kidney function. Sodium intake is strongly related to water intake via the thirst center. Therefore, sodium intake is strongly related to extracellular fluid volume, blood pressure, appetite, nutritional status, and mortality. To decrease mortality in both non-dialysis and dialysis CKD patients, sodium restriction is an essential and important factor that can be changed by the patients themselves. However, under sodium restriction, it is important to maintain the balance of negative and positive effects from sodium intake not only in dialysis and non-dialysis CKD patients but also in the general population.     

Amount and Food Sources of Sodium Intake by Individuals 62 Years and Older

Results on sources of sodium intake in diets of elderly populations were reviewed and accompanied by an examination of previously unreported results on dietary sources of sodium. Results from NFCS, NHANES I, NHANES II and this study showed average sodium intake levels (excluding discretionary salt) were in the range of 2,00 to 2,900 mg/day. Assessment of data from three sources strongly indicated that grain products were the major source of sodium in elderly individuals' diets. Meats and mixed protein dishes and milk and milk products were identified as two other food categories contributing large portions of sodium to diets. Individuals who were identified as having had greater than average daily sodium consumption intakes had the same principal food sources of sodium. Their increased sodium intakes were attributed to increased intake of all foods and to heavier usage of condiments, sauces and dips, and salted snack foods.     

Sodium Intake as a Cardiovascular Risk Factor: A Narrative Review

While sodium is essential for human homeostasis, current salt consumption far exceeds physiological needs. Strong evidence suggests a direct causal relationship between sodium intake and blood pressure (BP) and a modest reduction in salt consumption is associated with a meaningful reduction in BP in hypertensive as well as normotensive individuals. Moreover, while long-term randomized controlled trials are still lacking, it is reasonable to assume a direct relationship between sodium intake and cardiovascular outcomes. However, a consensus has yet to be reached on the effectiveness, safety and feasibility of sodium intake reduction on an individual level. Beyond indirect BP-mediated effects, detrimental consequences of high sodium intake are manifold and pathways involving vascular damage, oxidative stress, hormonal alterations, the immune system and the gut microbiome have been described. Globally, while individual response to salt intake is variable, sodium should be perceived as a cardiovascular risk factor when consumed in excess. Reduction of sodium intake on a population level thus presents a potential strategy to reduce the burden of cardiovascular disease worldwide. In this review, we provide an update on the consequences of salt intake on human health, focusing on BP and cardiovascular outcomes as well as underlying pathophysiological hypotheses.     

Assessing U.S. Sodium Intake through Dietary Data and Urine Biomarkers

Sodium intake is related to blood pressure, an established risk factor for heart disease and stroke. Reducing intake may save billions in United States health care dollars annually. Efforts targeting sodium reductions make accurate monitoring vital, yet limited information exists on the accuracy of the current data to assess sodium intake in the United States population. In this symposium, new findings were presented on the accuracy of estimating population 24-h urinary excretion of sodium from spot urine specimens or sodium intake from 24-h dietary recalls. Differences in accuracy by sex, BMI, and race were apparent as well as by timing of spot urine collections. Although some published equations appear promising for estimating group means, others are biased. Individual estimates of sodium intake were highly variable and adjustment for within-individual variation in intake is required for estimating population prevalence or percentiles. Estimates indicated United States sodium intake remains high.     

Factors Predicting Sodium Intake of Korean Americans with Type 2 Diabetes

The increasing prevalence of type 2 diabetes mellitus (T2DM) and its complications including cardiovascular disease and chronic kidney disease threaten Korean Americans (KAs). High dietary sodium intake contributes to both conditions. The purpose of the study was to assess dietary sodium consumption and to examine the predictors of sodium intake among KA with T2DM. A total 232 KA who had uncontrolled diabetes participated in this study. The majority of the sample (69%) consumed more sodium than current national guidelines. A high level of energy intake was the strongest predictor for sodium intake with gender and marital status also related. Our findings identified predictive factors to excessive sodium intake and these data support the need for culturally-tailored education about appropriate dietary sodium and energy intake are needed for patients about T2DM.     

Dietary Sources of Sodium Intake in Brazil in 2008-2009

Information on the main dietary sources of sodium is essential for developing public health strategies to reduce sodium intake. This study aimed to describe sodium intake according to sex, age, and income and identify the main dietary sources of sodium in Brazil. In total, 34,003 subjects aged 10 years and older participated in the first Brazilian National Dietary Survey, conducted in 2008-2009. Food was classified according to the sodium profile into 31 groups based on a 1-day food record. The daily per capita intake of sodium (mg/day) and sodium density (mg/100 g) were estimated for each food group and stratified by sex, age, and per capita income quartile. The average daily intake of sodium was 3,190 mg/day. The sodium density of the diet increased with age and income (P<0.05). Food groups with the highest densities for both sexes and across all income quartiles included salty preserved meats (997 mg/100 g), processed meats (974 mg/100 g), cheeses (883 mg/100 g), crackers (832 mg/100 g), sandwiches (800 mg/100 g), pizza (729 mg/100 g), and breads (646 mg/100 g), as well as oils, spreads, sauces, and condiments (804 mg/100 g). Altogether, these food groups contributed to 811 mg/day of sodium, which is more than half of the recommended daily sodium intake. Mean sodium intake in Brazil exceeded the tolerable upper intake level of 2,300 mg/day. Processed food contributed to half of the recommended intake and should be targeted by future public health policies aiming at reducing total sodium intake.     

Beyond Blood Pressure: New Paradigms in Sodium Intake Reduction and Health Outcomes

Since 1980, when inaugural national dietary guidance was to “avoid too much sodium,” recommendations have evolved to the 2010 Dietary Guidelines for Americans’ quantified guidance of 2300 and 1500 mg/d [USDA and U.S. Department of Health and Human Services. Dietary guidelines for Americans, 1st (http://www.cnpp.usda.gov/DGAs1980Guidelines.htm) and 7th (http://www.health.gov/dietaryguidelines/dga2010/dietaryguidelines2010.pdf) eds.]. Too much sodium remains a valid concern, but are current targets too low for optimal health? New research moves beyond sodium’s effect on the surrogate marker of blood pressure to examine the relation between sodium intake and cardiovascular morbidity and mortality. Results show that sodium intakes both less than and greater than ∼3000–5000 mg/d increase the risk of negative health outcomes. Additionally, newly compiled sodium intake data across populations show a uniformity that suggests that intake is physiologically set. Perhaps not coincidentally, the observed intakes fall within the range related to lowest risk. These findings are highly relevant to current efforts to achieve low sodium intakes across populations, because the data suggest that the efforts will be unsuccessful for healthy people and may cause harm to vulnerable populations. Remaining mindful of risks associated with both excessive and inadequate intakes is imperative with all nutrients, and sodium is no exception. Avoiding too much, and too little, sodium may be the best advice for Americans.Since 1980, national dietary guidance provided by the Dietary Guidelines for Americans (DGA)⁷ has targeted sodium reduction (1). Early dietary recommendations were qualitative, but more recently, DRIs quantified recommendations for sodium. Defining specific intake amounts is helpful to translate guidance into policy; however, the presence of quantified intake recommendations suggests certainty, which, in turn, has the potential to impede revising the recommendations as new science accumulates. This may be the case with sodium. Before the development of the DRIs, sodium’s estimated minimum average requirement for adults rested at 500 mg/d, the amount needed to maintain sodium balance under conditions of maximal adaptation and minimal loss. This level was never considered an amount to target for health, but it supported the framework that Americans’ sodium intake was excessive and deficiency would be unlikely. The focus on sodium reduction with no concern for inadequate intakes commenced. The physiologic relation between sodium, fluid electrolyte balance, and blood pressure provided a plausible mechanism by which sodium reduction would reduce blood pressure and was logically linked to the well-established correlation between elevated blood pressure and cardiovascular disease (CVD). Thus, sodium reduction to reduce blood pressure, which was thought to reduce CVD, was embraced. The current public health goal is to reduce Americans’ sodium intakes as much as possible, with the lower boundary of 1500 mg/d as the minimum amount of sodium required to consume in a nutritionally replete diet. But are current recommendations too low? Are these extremely low sodium intakes compatible with optimal health outcomes?The purpose of this symposium was to review a growing body of evidence examining sodium intake and health outcomes that are highly relevant to sodium DRIs, the DGA, and numerous government- and nongovernmental organization–driven efforts to significantly reduce sodium in the entire population. These new data must be examined to ensure that the assumed benefits of population-wide sodium reduction outweigh the potential risks, especially in vulnerable and ill populations.Dr. King began the program with a general overview of sodium recommendations, highlighting the evolution from the 1980 DGA’s guidance to “avoid too much sodium” to the 2010 DGA’s quantified guidance of 2300 and 1500 mg/d for those aged ≥51 y, and all people who are African American or have hypertension, diabetes, or chronic kidney disease (2). She compared the DGA’s to the historical Institute of Medicine (IOM) recommendations. The first time sodium recommendations were quantified appeared in the Food and Nutrition Board’s 1989 publication Diet and Health: Implications for Reducing Chronic Disease Risk (3). The maximum intake goal was set at 2400 mg on the basis of observational data from the 1988 InterSalt study publication showing that blood pressure increased with age in individuals with intakes >2400 mg (4). The only groups who consumed less sodium were those living in primitive societies. In fact, when the primitive societies were omitted, there was no relation between sodium intake and increasing blood pressure with age. Nonetheless, the recommendation of 2400 mg as a maximum intake was adopted by authoritative bodies until 2005 when the DRI for sodium was set at 2300 mg as the upper level on the basis of 2 dose-response studies on blood pressure. The adequate intake was set at 1500 mg on the basis of modeling the minimum amount of sodium required to achieve a nutritionally adequate diet. (It should be noted that the modeled diet contained primarily reduced-sodium foods, many of which may not be readily available, such as reduced-sodium bread.) In 2005 and 2010 the DGA adopted these levels.Perhaps due to the assumption that reducing sodium reduces blood pressure and therefore must reduce CVD, and assuredly because of the difficulty in conducting studies to examine sodium and health outcomes, the direct relation between sodium reduction and health outcomes had largely been overlooked in the literature until recently. Now, a critical mass of data relating both greater and lesser intakes of sodium to increased risk of outcomes such as death, CVD, and heart failure, has begun to emerge, and these data were reviewed in the 2013 IOM report “Sodium Intake in Populations: Evaluation of the Evidence” (5). Examination of the new evidence brought findings that were surprising, showing that current sodium intake recommendations may pose risk. But were they really surprising?Dr. Heaney reminded the audience that these findings were exactly what could be expected based on the physiology of all nutrients. That is, the relation between a nutrient intake and health benefit is not a straight line that intersects with zero on the x and y axis, indicating that lower is better, but instead is a J-shaped curve that indicates risk at both ends of intake, with a rather wide range of “no harm” (or benefit) at intakes between these extremes. It is within this range, wherein the organism needs to exert minimal compensation, that nutrient requirements are typically set. Heaney outlined in his presentation the unexplained departure from the evidence-based approach for sodium. In fact, even with the use of blood pressure as a surrogate marker of benefit, the DASH (Dietary Approaches to Stop Hypertension) study shows that a focus on food and dietary patterns that provide adequate potassium, calcium, and magnesium create a more meaningful blood pressure effect and do not pose the potential harm of very low sodium intakes. Revisiting the sodium DRIs with consideration of the evidence on health outcomes and approaching the task adhering to the agreed-upon evidence-based process are critical to the integrity of nutrient recommendations, of which sodium should be no exception.Dr. Alderman presented the historic path of health outcomes–related sodium intake research. Published research as well as plausible physiologic mechanisms such as the renin-angiotensin-aldosterone system have long existed that refute benefit of sodium reduction to low amounts, but these data have been overshadowed until recently. Alderman was among the first to report the inverse relation between renin and myocardial infarction. Reduced sodium intake leading to increased renin concentrations is an example of sodium restriction not exerting the singular physiologic effect of blood pressure reduction, but instead shows how it exerts multiple effects, including negative consequences such as increased plasma renin activity, increased insulin resistance and sympathetic nerve activity, and elevated aldosterone and TGs. The net health effect cannot be predicted by the consequence on blood pressure alone. Alderman was also the first to suggest the J-shaped risk curve for CVD and sodium intake, and this hypothesis was supported by the 2013 IOM report. Subsequent to the 2013 IOM report, several additional papers have supported the J-shaped risk curve, including the 2014 Graudal et al. meta-analysis summarizing findings from 274,683 individuals from 25 studies (6). The idea that the blood pressure effect of sodium restriction can be extrapolated to a health benefit no longer retains scientific credibility.Dr. McCarron capped the session by presenting a body of data showing the narrow sodium intake ranges observed in 69,011 people from 45 countries around the world gathered over the past 50 y, which are remarkably constant and appear to be independent of the food supply. The mean intake is 3600–3700 mg/d, and the mean population minimum and maximum are 2622 and 4830 mg/d, respectively. Mean intakes of the Adequate Intake of 1500 mg or the Tolerable Upper Intake Level of 2300 mg are not observed in these free-living healthy populations. He pointed out that interpreting reductions in sodium intake caused by reducing sodium in commercially prepared foods, such as in the United Kingdom, are in fact small variations within 1 SD of the mean. The data support that intake of sodium is not mediated by the food supply but is physiologically controlled through sodium appetite. The risk of reducing sodium below this “set point” is consistent with the increased morbidity and mortality observed at the lowest sodium intakes (similar to current recommendations) that have been reported by several researchers and reiterated in the IOM report.Common ground among all who study sodium intake and health outcomes is that excess sodium intake carries increased risk of morbidity and mortality. The controversy focuses on the lower end of sodium intake. Although public health guidelines continue to promote intakes <2300 mg/d, data suggest that this amount may be too low for optimal health. The recommended intakes do not cause concern for free-living individuals who have access to salt, but they do have direct implications for hospitalized patients, nursing home residents, and school feeding programs and other government-funded feeding programs that must adhere to these guidelines. Additionally, if, in fact, sodium intake is set physiologically, current resources being poured into sodium reduction by public and commercial entities could be more effectively spent on important innovations related to public health, such as increasing demand for smaller portion sizes, improving availability of lower-energy-dense food, and replenishing food deserts.This session helped bring awareness to the potential risk associated with intakes at currently recommended amounts, amounts of intake that are lower than any observed in modern free-living healthy populations regardless of food supply. New data support a J-shaped curve for risk, with the intakes related to least harm being those between ∼3000 and 5000 mg, a range that includes the current usual intakes of the majority of healthy individuals in the world.The convergence of new data from research focused on health outcomes and newly compiled sodium intake amounts suggests that enforcing very low sodium intakes will at best fail for most people and at worst cause harm for vulnerable or ill individuals subjected to the recommended levels. Perhaps the 1980 DGA statement of “avoid too much sodium” really had it right, with 1 revision: “avoid too much—and too little—sodium.”