Individual Salt Intake Research Articles

Long-term variability of urinary salt excretion and blood pressure in hypertensive patients.

We investigated the long-term trend and variability of urinary salt (sodium chloride) excretion in hypertensive patients. Subjects included 186 hypertensive patients (103 women and 83 men, mean age: 58.5±10.5 years) who underwent 10 successful 24-h home urine collections over a mean observation period of 7.7 years. We measured 24-h urinary salt excretion and blood pressure (BP) sequentially at the time of each collection and monitored the long-term trend and variability of urinary salt excretion. BP significantly decreased from 145±16/85±11 mm Hg to 130±12/70±11 mm Hg and was associated with an increased use of antihypertensive drugs. The 24-h urinary salt excretion also decreased from 9.5±3.6 g per day at the first measurement to 8.5±3.2 g per day at the 10th measurement. Urinary salt excretion during the observation period ranged from a minimum value of 5.2±1.8 g per day to a maximum value of 13.4±3.6 g per day with a coefficient of variation of 29.2±8.1%. When subjects were assigned to a low, medium and high salt group based on the tertiles of the first measurement of urinary salt excretion and the tertiles based on the mean value of 10 measurements during the observation period, only 56.2% remained in the same category, suggesting that a single measurement of urinary salt excretion can only predict long-term urinary salt excretion in approximately half of the individuals. In conclusion, urinary salt excretion shows large variability such that a single measurement may not be sufficient to assess salt intake in individuals.

The prevalence and characteristics of microalbuminuria in the general population: a cross-sectional study

BackgroundMicroalbuminuria is a marker of cardiovascular events. This study investigated the prevalence of microalbuminuria in the general population and the factors that can affect urinary excretion of albumin.MethodsApparently healthy subjects who participated in a health checkup at our hospital were enrolled in this study (n = 7963, male 64.0%, 56.2 ± 11.8 years old) Urine samples were collected for the measurement of albumin concentrations, which were expressed as the ratio of urinary albumin to creatinine concentrations (UACR [mg/g Cr]). Individual salt intake was assessed by estimating the 24-hour urinary salt excretion of subjects.ResultsThe mean blood pressure was 124 ± 15/76 ± 10 mmHg and 31.6%, 7.4%, and 44.1% of subjects had hypertension, diabetes mellitus, and dyslipidemia, respectively. Urinary albumin was detected in 7265 subjects (91.2%: UACR ≥ 300 mg/g Cr, 0.5%; 300 > UACR ≥ 30 mg/g Cr, 4.6%; 30 > UACR ≥ 20 mg/g Cr, 2.4%; 20 > UACR ≥ 10 mg/g Cr, 8.7%; 10 > UACR ≥ 5 mg/g Cr, 21.8%; UACR < 5 mg/g Cr, 53.2%). In subjects with detectable albuminuria, UACR was independently correlated with age, systolic blood pressure, serum creatinine, fasting plasma glucose, and salt intake after adjustment for possible factors (P < 0.0001).ConclusionThe prevalence of microalbuminuria was found to be 4.6% in the general population. The urinary excretion of albumin was closely associated with blood pressure and salt intake. These data indicated the importance of salt restriction for the prevention of cardiovascular disease and end-stage renal disease.

Second morning urine method is superior to the casual urine method for estimating daily salt intake in patients with hypertension

The accuracy of the casual urine (CU) method for estimating daily salt intake was compared with the second morning urine (SMU) method and with 24-h urine collection (24 UC) method as the gold standard. Data were obtained from three previously reported studies, in which we evaluated the daily salt intake by the SMU method. Using SMU samples from 1315 outpatients, the estimated salt intake was lower with the CU method than the SMU method. In inpatients with a daily salt intake of 7, 8 or 18 g, the CU method was applied to SMU specimens. It underestimated salt intake compared with the 24-h collection method whereas the SMU method and 24 UC method gave similar results. In the present study, 24 UC was done and then urine was collected at 0800, 1100, 1400, 1700 and 1900 hours, with a daily salt intake of 6 g in 8 inpatients, 10 g in 11 inpatients or 15 g in 5 inpatients. In comparison with the 24 UC method, the CU method underestimated a high salt intake (15 g) when morning specimens were used and overestimated a low salt intake (6 g) when afternoon specimens were used. The correlation between the CU method and 24 UC method was weaker (R = 0.57) than that between the SMU method and 24 UC method (R = 0.85). In conclusion, the CU method is heavily influenced by the timing of urine collection and by the actual daily salt intake, so the SMU method provides a better estimate of individual salt intake.

Factors associated with brachial-ankle pulse wave velocity in the general population

The present study investigated factors that modify or affect arterial stiffness as assessed by brachial-ankle pulse wave velocity (baPWV) in the general population. Subjects had previously participated in a physical checkup program (n=911), and baPWV and urinary albumin and sodium excretion were also measured. Urine albumin was expressed as the ratio of urine albumin to urine creatinine. Individual salt intake was assessed by estimating 24-h urinary salt excretion and expressed as the ratio of estimated salt intake to body weight. The mean blood pressure and baPWV were 127.1±15.2/77.0±9.5 mm Hg and 15.9±3.3 m s(-1), respectively. Univariate analysis demonstrated that baPWV correlated with various factors including age, blood pressure, electrocardiogram voltage (SV(1)+RV(5)), urine albumin and salt intake. Multivariate regression analysis revealed that electrocardiogram voltage (P<0.001), systolic blood pressure (P<0.0001), urine albumin (P<0.001) and salt intake (P<0.001), independently correlated with baPWV after adjustment for other possible factors. Similar results were obtained for participants not taking any medication. These results suggest that the baPWV value is independently associated with individual salt intake and cardiac and renal damage, and could be a useful procedure for identifying individuals with concealed risk of cardiovascular disease.

Dietary Salt Intake and Blood Pressure in a Representative Japanese Population: Baseline Analyses of NIPPON DATA80

BackgroundThe relationship between dietary salt intake and blood pressure (BP) has been rarely investigated in a large population of Japanese. The characteristics of nutrients intake and foods intake in Japanese people with high salt intake have also not investigated well.MethodsData of 10 422 participants (4585 men and 5837 women) aged 30 or older who participated in both the National Survey on Circulatory Disorders and National Nutrition Survey in Japan conducted in 1980 were used. The nutrition surveys were performed with weighing record method for three consecutive days to each household. BP and intakes of nutrients and foods were compared by the quintiles of estimated individual salt intake per day. Analyses of covariance were used to calculate multivariate-adjusted mean BP values by the quintiles.ResultsParticipants with higher salt intake showed higher intakes of soy beans/legume, fruit, other vegetables, and fish/shellfish. Intakes of protein, potassium, calcium, iron, magnesium, and fiber were higher in higher quintiles of salt intake. In men, adjusted systolic BPs were higher in the higher salt intake quintiles; there was 4.3 mm Hg difference in multivariate-adjusted systolic BP between the lowest quintile (mean salt intake 8.7 g/day) and the highest quintile (mean salt intake 23.5 g/day) (P < 0.001). In women, adjusted mean systolic BPs were not statistically different among the quintile of salt intake.ConclusionsA positive relationship of dietary salt intake to BP was observed, especially in men, in this large-scale representative Japanese population.

Salt intake in individuals with metabolic syndrome

Salt intake in individuals with metabolic syndrome

Salt Sensitivity

Although increases in dietary NaCl (referred to as salt in this article) intake expand extracellular fluid volume and elevate mean arterial pressure (MAP) even in healthy subjects, the magnitude of the response varies with some individuals demonstrating remarkable resistance to the hypertensive effects of salt intake despite ingestion of very high doses.1 Salt sensitivity therefore refers to the propensity for changes in salt intake to produce meaningful increases in mean arterial pressure (MAP). The endless debate regarding whether the amount of salt ingested affected blood pressure sufficiently to alter life span was effectively curtailed by the Trials of Hypertension Prevention studies, which showed that dietary salt reduction decreased the long-term risk of cardiovascular events by 25% in patients who had prehypertension, confirming an important effect of salt intake on the cardiovascular system.2 In addition, the landmark work of Weinberger and colleagues provided convincing evidence that normotensive subjects who demonstrated salt sensitivity had a subsequent cumulative mortality that rivaled that of hypertensive patients.3 How salt intake alters cardiovascular function remains …

Report of the Working Group for Dietary Salt Reduction of the Japanese Society of Hypertension: (2) Assessment of Salt Intake in the Management of Hypertension

Restriction of dietary salt is widely recommended in the management of hypertension, but assessment of individual salt intake has drawn little attention. The understanding of salt intake is important as a guide for optimizing salt-restriction strategies. However, precise evaluation of salt intake is difficult. More reliable methods are more difficult to perform, whereas easier methods are less reliable. Thus, the method to assess salt intake should be determined as the situation demands. The Working Group for Dietary Salt Reduction of the Japanese Society of Hypertension recommends the assessment of individual salt intake using one of the following methods in the management of hypertension. 1) The measurement of the sodium (Na) excretion from 24-h urine sampling or nutritionist's analysis of the dietary contents, which are reliable but difficult to perform, are suitable for facilities specializing in the treatment of hypertension. 2) Estimation of the Na excretion from the Na/creatinine (Cr) ratio in spot urine is less reliable but practical and is suitable for general medical facilities. 3) Estimation using an electronic salt sensor equipped with a calculation formula is also less reliable but is simple enough that patients can use it themselves. The patients are considered to be compliant with the salt-restriction regimen if salt intake measured by whichever method is less than 6 g (100 mmol)/day.