Dietary sodium and cardiovascular and renal disease risk factors: dark horse or phantom entry?

Understanding the patterns and trends of sodium intake, potassium intake, and sodium to potassium ratio and their effect on hypertension in China

BACKGROUND

Recent studies have shown inconsistent effects of sodium reduction, potassium intake, and the ratio of sodium to potassium (Na/K ratio) on hypertension and other cardiovascular diseases. Major gaps exist in knowledge regarding these issues in China.

OBJECTIVE

We analyzed the patterns and trends of dietary sodium intake, potassium intake, and the Na/K ratio and their relations with incident hypertension in China.

DESIGN

The China Health and Nutrition Survey cohort includes 16,869 adults aged 20-60 y from 1991 to 2009. Three consecutive 24-h dietary recalls and condiment and food weights provided detailed dietary data. Multinomial logistic regression models determined trends and patterns of sodium and potassium intake and the Na/K ratio. Models for survival-time data estimated the hazard of incident hypertension.

RESULTS

Sodium intake is decreasing but remains double the Institute of Medicine recommendations. Most sodium comes from added condiments. Adults in the central provinces have the highest sodium intake and the most rapid increase in hypertension. Potassium intake has increased slightly but is below half of the recommended amount. The Na/K ratio is significantly higher than the recommended amounts. Recent measurements of high sodium intake, low potassium intake, and high Na/K ratio have strong independent dose-response associations with incident hypertension.

CONCLUSIONS

Reducing sodium in processed foods, the major public health strategy in Western countries, may be less effective in China, where salt intake remains high. Replacing sodium with potassium in salt to control and prevent hypertension in China should be considered along with other public health and clinical prevention options.

Removing salt sachets from ward meal-trays does not affect patients' nutritional intake

BACKGROUND

Reducing dietary salt intake lowers blood pressure and proteinuria, both of which are beneficial in preventing renal disease progression. Hospital meals are often accompanied by salt sachets, providing patients with additional salt.

OBJECTIVES

The aim of this study was to determine the effects of salt sachet provision by request only (i.e., the patient must ask for a salt sachet rather than the sachet being placed automatically on the tray), on meal consumption and salt intake. A secondary aim was to determine policy on salt sachet provision in other hospitals.

DESIGN

Salt sachet use and meal consumption was assessed on a renal ward over two weeks. Salt sachets were then provided 'by request only' and the assessment was repeated. Renal Nutrition Group members were surveyed to determine the policy of sachet provision in other hospitals.

RESULTS

Salt intake was significantly reduced during the period when salt was provided by request only compared with routine salt provision (p < 0.01). Meal consumption was similar during both periods. Salt sachet provision varied by hospital.

CONCLUSION

Providing salt sachets by 'request only' reduced salt intake without affecting meal consumption. This is now the adopted policy on the renal ward at our hospital.

Short-term effects of hypertonic saline solution in acute heart failure and long-term effects of a moderate sodium restriction in patients with compensated heart failure with New York Heart Association class III (Class C) (SMAC-HF Study)

INTRODUCTION

Hypertonic saline solution (HSS) and a moderate Na restriction plus high furosemide dose showed beneficial effects in compensated heart failure (HF), in short and long terms. The study was aimed to verify the effects of this combination on hospitalization time, readmissions and mortality in patients in New York Heart Association (NYHA) class III.

METHOD

Chronic ischemic or nonischemic cardiomyopathy uncompensated patients with HF in NYHA III functional class with ejection fraction <40%, serum creatinine <2.5 mg/dL, blood urea nitrogen <60 mg/dL and reduced urinary volume were single-blind randomized in 2 groups: the first group received a 30-minute intravenous infusion of furosemide (250 mg) plus HSS (150 mL) twice daily and a moderate Na restriction (120 mmol); the second group received furosemide intravenous bolus (250 mg) twice a day, without HSS and a low Na diet (80 mmol); both groups received a fluid intake of 1000 mL/d. After discharge, the HSS group continued with 120 mmol Na/d; the second group continued with 80 mmol Na/d.

RESULTS

A total of 1771 patients (881 HSS group and 890 without HSS group) met inclusion criteria: the first group (881 patients), compared with the second (890 patients), showed an increase in diuresis and serum Na levels, a reduction in hospitalization time (3.5 + 1 versus 5.5 + 1 days, P < 0.0001) and, during follow-up (57 + 15 months), a lower rate in readmissions (18.5% versus 34.2%, P < 0.0001) and mortality (12.9% versus 23.8%, P < 0.0001); the second group also showed a significant increase in blood urea nitrogen and serum creatinine.

CONCLUSION

This study suggests that in-hospital HSS administration, combined with moderate Na restriction, reduces hospitalization time and that a moderate sodium diet restriction determines long-term benefit in patients with NYHA class III HF.

The relationship between hypertension and salt intake in Turkish population: SALTURK study

This population-based epidemiological study was aimed to evaluate the daily salt intake and its relation to blood pressure in a representative group of Turkish population. The enrolled normotensive and hypertensive individuals (n = 1970) completed a questionnaire including demographics, dietary habits, hypertension awareness and drug usage. Blood pressure was measured and to estimate salt consumption, 24-h urine samples were collected. The daily urinary sodium excretion was 308.3 ± 143.1 mmol/day, equal to a salt intake of 18.01 g/day. Salt intake was higher in obese participants, rural residents, participants with lower education levels and elderly. A positive linear correlation between salt intake and systolic and diastolic blood pressures was demonstrated (r = 0.450, p = 0.020; r = 0.406, p = 0.041; respectively), and each 100 mmol/day of salt intake resulted in 5.8 and 3.8 mmHg increase in systolic and diastolic blood pressures, respectively. Salt intake and systolic blood pressure was significantly correlated in normal weight individuals (r = 0.257, p < 0.01). The Turkish population consumes a great amount of salt; salt intake and blood pressure was positively correlated. Efforts in sodium restriction are therefore crucial in the management of hypertension as part of national and global health policies.

Salt restriction for the prevention of cardiovascular disease

BACKGROUND

Restricting the dietary intake of sodium chloride is associated with a reduction of the arterial blood pressure by approximately 4/2 mm Hg in hypertensive patients and by approximately 1/0.6 mm Hg in normotensive persons. As the cardiovascular risk is known to rise steadily with systolic blood pressure values starting from 115 mm Hg, lowering the mean blood pressure of the general population by dietary salt restriction would seem to be a practicable form of primary prevention of cardiovascular disease.

METHOD

Selective literature search and review.

RESULTS

Multiple studies have shown dietary salt restriction to be associated with lower cardiovascular morbidity and mortality. The reduction of adjusted relative risk in controlled observational studies ranges from 25% over 15 years to 41% over three years.

CONCLUSION

On the basis of the available studies, it seems likely that a moderate lowering of the daily intake of sodium chloride by the general population from 8 to 12 grams per day (the current value) to 5 to 6 grams per day would be a useful public health measure, with economic benefits as well. The potential risks for certain groups of individuals are foreseeable and controllable. A general reduction of dietary salt intake can only be achieved by reducing the sodium chloride content of industrially processed foods, as these account for 75% to 80% of the sodium chloride consumed daily. Aside from a general reduction of dietary salt intake, further important primary prevention measures for the general population include changes in lifestyle and in dietary habits.

Low dietary sodium intake increases the death risk in peritoneal dialysis

BACKGROUND AND OBJECTIVES

To explore the correlation between dietary sodium intake and cardiovascular and overall mortality, and then determine whether this correlation can be explained by protein and energy intake paralleled with sodium intake in dialysis patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This single-center retrospective cohort study enrolled 305 incident patients who started peritoneal dialysis in our unit from July 2002 to February 2007. All patients were followed until death or until being censored in February 2008. Demographic data were collected at baseline. Biochemical, dietary, and nutrition data were examined at baseline and thereafter at regular intervals to calculate the average values throughout the study.

RESULTS

Participants with the highest average sodium intake were more likely to be younger, male, and overweight. Patients in the high tertile of average sodium intake had higher albumin, prealbumin, and lean body mass levels, and more nutrient intakes paralleling with sodium intake. Low average sodium intake independently predicted the increased risk for overall and cardiovascular death after adjusting for recognized confounders. Further adjustment for dietary protein, energy, and other nutrient intakes individually had minimal impact on the association between average sodium intake and overall death, with hazard ratios varying between 0.35 and 0.44, and cardiovascular death, with hazard ratios varying between 0.06 and 0.11.

CONCLUSIONS

This study revealed that low dietary sodium intake independently predicts the high overall and cardiovascular mortality in dialysis patients. This correlation could not be entirely explained by deficient protein and energy intake.