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Salt-reduction guidance to hypertensive patients should be performed by evaluating salt intake of the individuals. However, each method to assess salt intake has both merits and limitations. Therefore, evaluation methods must be selected in accordance with the subject and facility's environment. In special facilities for hypertension treatment, measurement of sodium (Na) excretion with 24-h pooled urine or a survey on dietary contents by dietitians is recommended. In medical facilities in general, measurement of the levels of Na and creatinine (Cr) using second urine samples after waking-up or spot urine samples is recommended. The reliability of this method improves by using formulae including a formula to estimate 24-h Cr excretion. A method to estimate salt intake based on the Na excretion per gram Cr using the Na/Cr ratio in spot urine is simple, but not reliable. The method to estimate the daily excretion of salt from nighttime urine using an electronic salt sensor installed with a formula is recommended to hypertensive patients. Although its reliability is not high, patients themselves can measure this parameter simply at home and thus useful for monitoring salt intake and may intensify consciousness regarding salt reduction. Using these methods, salt intake (excretion) should be evaluated, and salt-reduction guidance targeting6 g (Na: 100 mmol) per day should be conducted in the management of hypertension.

Dietary salt consumption is closely associated with the level of blood pressure (BP); stricter salt reduction more markedly decreased BP. Obesity/metabolic syndrome, Dietary Approach to Stop Hypertension (DASH) diet, exercise and mental stress influence the BP-elevating effect of high-salt diet. Observational and intervention studies suggested that salt restriction improved the risk of cardiovascular diseases. However, the effects may differ among the types of the hypertensive complications; salt reduction may decrease the risk of stroke more than that of ischemic heart disease. Small-scale studies demonstrated that excess salt increased the risk of the left ventricular hypertrophy, heart failure, the urinary protein/albumin levels and end-stage renal failure. These diverse beneficial effects of salt reduction are probably because low-salt diet is an effective strategy to decrease BP and body fluid volume but is less effective to ameliorate the other cardiovascular risk factors. A mean salt intake in Japan is markedly high. Considering the present condition, salt reduction is essential for the prevention and treatment of hypertension and for the prevention of cardiovascular diseases.

In this section of the Report of the Salt Reduction Committee of the Japanese Society of Hypertension, the target level of dietary salt reduction and its scientific evidence, present status of salt consumption in Japan, salt-reducing measures/guidance methods in individuals and population strategies to reduce salt intake are introduced. In the Dietary Reference Intake for the general population in Japan (2010 version), the target levels of salt restriction in men and women were established as less than 9.0 per day and 7.5 g per day, respectively. The Japanese Society of Hypertension Guidelines for the Management of Hypertension 2009 recommended the target level of dietary salt restriction in patients with hypertension as less than 6 g per day. However, the National Health and Nutrition Survey of Japan in 2010 reported that the mean salt intake in adults was 10.6 g per day (men: 11.4 g per day and women: 9.8 g per day). To effectively decrease salt intake in Japan, it is necessary to reduce the consumption of high-salt foods (especially traditional foods) and replace high-salt seasonings (soy sauce and so on) with low-salt alternatives. Health-care professionals must effectively perform salt-reduction guidance for hypertensive patients in hospitals/administrative organizations. To promote population strategies for salt reduction in the whole society of Japan, social strategies, such as administrative policies, companies' cooperation and educational staff's cooperation, are necessary.

The second morning urine (SMU) method was developed to evaluate daily salt intake, but the posture that should be adopted until the SMU collection remains unclear. This study investigated the influence of posture in hypertensive patients who underwent this test. The subjects were 100 patients who could collect 24-h urine samples correctly and were on a diet containing 7 g of salt per day. Their daily salt intake was estimated for three consecutive days in the recumbent, sitting, and sitting and standing positions (one posture each day). Estimated salt intake in the recumbent position (10.9+/-2.4 g day(-1)) was higher than in the sitting position (7.5+/-2.0 g day(-1)) and the sitting and standing position (6.3+/-1.7 g day(-1)). The salt intake estimated in the sitting and standing position was similar to that obtained by 24-h urine collection (6.3+/-1.6 g day(-1)) and was significantly (r=0.44, P0.05) correlated with the 24-h urine value. The actual difference in estimated salt intake between the two methods was 0.0+/-1.7 g day(-1). There were no significant differences in estimated salt intake between the two methods in patients taking different classes of antihypertensive drugs. In conclusion, adopting the sitting and standing position until the SMU collection is important for the correct estimation of daily salt intake, and this method could replace the 24-h collection method because of its convenience, especially in outpatients.

To determine the factors that affect seasonal variation in blood pressure (BP) in a fairly large number of patients with essential hypertension who stayed almost entirely indoors in a stable environmental temperature and who took a calcium channel blocker during the study. This prospective study of hypertensive patients was conducted during the summer and winter. BP was measured by ambulatory blood pressure monitoring; the indoor temperature was measured at the time of the BP measurement using an electrothermometer with the subject awake and indoors. Subjects comprised 38 men and 57 women. The subjects spent virtually the entire day indoors during both the summer (men, 22.1±1.6h; women, 23.0±0.9h) and winter (men, 23.0±0.9h; women, 22.9±0.9h). During the waking hours, the systolic/diastolic BPs were significantly higher during the winter than the summer. The differences were 8±9/4±5mmHg in men and 5±11/2±6mmHg in women; these values were not significantly different between men and women. No significant seasonal differences in BP during the sleeping hours were noted. There was a significant difference of approximately 6°C in the environmental temperature during waking hours, but there was no significant difference in urinary excretion of sodium or in exercise activity between the seasons. Only body height was significantly correlated with the winter increase in waking BP in both men and women, even after adjustment for potential confounding variables. Body height was a determinant of the increase in waking BP during the winter in hypertensive patients who lived almost entirely indoors. (Hypertens Res 2000; 23: 587-592)

To evaluate the effects of prolonged intake of a high-sodium diet on glucose and lipid metabolism, we examined the relation of daily urinary sodium excretion to blood pressure, glucose metabolism, and lipid metabolism in 140 Japanese adults who lived in a region where the average daily consumption of sodium was high and stable during the past 15 yr; no subject had received any treatment for hypertension or metabolic disorders. Each subject was admitted to our health examination center for 2 d for measurement of blood pressure, sampling of blood, and glucose tolerance testing. A 24-h urine specimen was collected by each subject after discharge. Multiple regression analysis revealed that urinary sodium excretion was significantly independent of the mean blood pressure and was unrelated to the area under the serum glucose curve after glucose administration. The urinary sodium level was also unrelated to low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol. The prevalence of hypertension in the group with a daily sodium excretion below 140 mEq (low sodium group) was 0%, while that in the group with a daily sodium excretion above 280 mEq (high sodium group) was 44%; this difference was significant (p < 0.01). No significant difference was observed in the prevalence of metabolic disorders between the two groups. Our results suggest that sodium intake has little influence on glucose and lipid metabolism but has a significant influence on blood pressure in normotensive and untreated hypertensive subjects who reside in an area with a relatively high sodium intake.

We investigated the correlations between the reduction in body weight (BW) induced by calorie restriction and reductions in blood pressure (BP) and improvement in metabolic disorders in overweight women with essential hypertension. After eating a standard diet (diet-I) for 2 weeks, women in the calorie-restricted group (n=25) received a low calorie diet for 2 weeks, and then standard diet-II for 1 week. Women in the calorie-nonrestricted group (n=13) ate standard diet-I for 5 weeks. The calorie-restricted group exhibited a significant reduction in BP in association with loss of BW; their levels of low-density lipoprotein cholesterol, and triglycerides levels, and their fasting levels of glucose and insulin were also reduced compared with the calorie-nonrestricted group. However, there were no significant differences in the level of high-density lipoprotein cholesterol, the areas under the 2-h glucose and insulin curves (AUCglu and AUCins), or the ratio of AUCglu to AUCins between groups. The change in BW was significantly correlated with a reduction in BP (r=0.62, p

This study was performed to elucidate the effect of a hypocaloric diet on blood pressure and sodium balance in overweight women with essential hypertension. Hospitalized patients were fed a hypocaloric diet (900 kcal/day) for 3 weeks after being fed a standard diet (SD) for more than 2 weeks. During the study, the sodium and potassium intake was kept constant as was the level of exercise activity. After the mean arterial pressure (MAP) and body weight had stabilized during the last week on the SD, caloric restriction significantly reduced the body weight by 1.5kg in the first week and by 0.8-0.9 kg in subsequent weeks, and reduced the MAP by 5mmHg and by 1-3mmHg, respectively. Although caloric restriction reduced the excretion of urinary norepinephrine and C-peptide, and elevated the serum levels of ketone bodies that would induce natriuresis, the urinary sodium excretion remained unchanged, indicating that sodium balance was unchanged even by caloric restriction. These results suggest that caloric restriction lowers the blood pressure in a short time with no significant change in sodium balance. (Hypertens Res 1992; 15: 137-142)