Urinary Excretion of Sodium and Potassium in a Screened Cohort in Okinawa, Japan.

Abstract

Information regarding daily intake of sodium (Na) is useful for both normotensive and hypertensive subjects. We measured urinary excretion of sodium (U-Na) and urinary excretion of potassium (U-K) to estimate daily salt intake in a cohort of health screening subjects in Okinawa, Japan. Urine samples were obtained from 2,411 subjects (1,554 men and 857 women) who were examined on a half-day dry-doc at the Okinawa General Health Maintenance Association (OGHMA). Four hundred and one subjects were examined twice, once between September and November in 1997, and once between September and November in 1998. The mean U-Na was 182 mEq/day for men and 176 mEq/day for women. The mean U-K was 54 mEq/day for men and 50 mEq/day for women. U-Na was higher in young men, and U-K was lower in young women. In both men and women, smokers had a significantly lower Na excretion compared to nonsmokers. Subjects treated for hypertension had a significantly lower Na excretion (173 mEq/day) compared to subjects not treated for hypertension (192 mEq/day). Our findings suggest that Na excretion in screened subjects in Okinawa is lower than the national average. Sodium excretion, however, was higher in young men than in elderly subjects, and K excretion was lower in young women than in elderly subjects. Both trends are disadvantageous for controlling hypertension.

Estimated Protein Intake and Blood Pressure in a Screened Cohort in Okinawa, Japan

“…The present data showed that the average intake of protein is not high in Okinawa. We also reported that the salt intake was smaller than that of the Japanese national average (14). Therefore, we speculate that the high incidence of ESRD in Okinawa is not directly related to dietary habits.…”

Low daily salt intake is correlated with albuminuria in patients with type 2 diabetes

“…The logarithm of urinary albumin excretion in the third quartile was significantly lower than in the first (Po0.01) or second (Po0.05) quartile of daily salt intake. *Cut points for the quartiles of daily salt intake were 8, 10 and 12 g. Low daily salt intake and albuminuria K Sakabe et al values obtained from the spot urine method correlated highly with those obtained from 24-h urinary sodium excretion, 19 and the usefulness of the spot urine method has been confirmed in population studies 20 and in hypertensive patients. 21 We speculate that excessive dietary salt restriction leads to increased angiotensin II and aldosterone levels, chiefly via an increase in plasma renin activity.…”

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

“…Daily sodium excretion values obtained by the SMU method show a strong correlation with those estimated by the 24-h collection (R¼0.73). The usefulness of the SMU method has been confirmed in population studies 5,11,12 and in hypertensive patients. 13 Although the posture that should be adopted for the SMU method was not specified by the original authors, 10 posture is known to affect the urinary sodium:creatinine ratio 14,15 and could possibly influence the estimation of daily salt intake by this method.…”