The influence of posture on the estimation of daily salt intake by the second morning urine method

Abstract

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 À1 ) was higher than in the sitting position (7.5 ± 2.0 g day À1 ) and the sitting and standing position (6.3 ± 1.7 g day À1 ). 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 À1 ) and was significantly (r¼0.44, Po0.05) 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 À1 . 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.

Validation of the equations for estimating daily sodium excretion from spot urine in patients with chronic kidney disease

“…Second, the influence of posture on the estimate was not evaluated. When using Kawasaki's equation, it is suggested that the urine should be collected in a sitting or standing position to maintain accuracy [19]. All of the patients who participated in this study were outpatients, and they probably collected the first morning urine just after they woke up.…”

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

“…12 Daily salt intake is evaluated by measuring the ratio of sodium to creatinine in the SMU specimen and by calculating daily creatinine excretion as reported previously. 13 We have found that the accuracy of estimating the daily salt intake by the SMU method is equal to that of the 24UC method if the subject maintains the sitting or standing position until the SMU sample is collected, 14 and we have also shown that this method was useful in patient on antihypertensive therapy. 14,15 On the other hand, Tanaka et al 16 have developed a simple casual urine (CU) method for public health research.…”

“…13 We have found that the accuracy of estimating the daily salt intake by the SMU method is equal to that of the 24UC method if the subject maintains the sitting or standing position until the SMU sample is collected, 14 and we have also shown that this method was useful in patient on antihypertensive therapy. 14,15 On the other hand, Tanaka et al 16 have developed a simple casual urine (CU) method for public health research. With the CU method, a urine sample can be collected during the daytime between 0800 hours and 1900 hours, whereas urine is generally collected between 0800 hours and 1000 hours for the SMU method.…”

“…Second, we reported that the posture before collection of the SMU sample was important for correctly estimating daily salt intake by the SMU method. 14 In studies A and B, as well as the present study, the subjects did not adopt a recumbent posture before the SMU collection. In study C, however, urine collection was done without any restrictions on posture because we did not recognize the importance of posture at that time (although the patients did not adopt the recumbent position according to their diary records).…”

A long-term, comprehensive exercise program that incorporates a variety of physical activities improved the blood pressure, lipid and glucose metabolism, arterial stiffness, and balance of middle-aged and elderly Japanese

“…Urinary concentrations of sodium (Na), potassium (K) and creatinine (Cr) were measured, and 24-h excretions of Na and K were estimated by our established method. [23][24][25][26][27] To confirm the consistency of the participants' diet over the study period, urinary concentrations of calcium (UCa) and magnesium (UMg) were also measured, and the UCa/UMg ratio was calculated. Urinary urea nitrogen (UN) was measured and the UN/UCr the ratio was calculated before and after the study period for each participant to roughly estimate the stability of the nutrient intake.…”