Urinary excretion of sodium and potassium in a screened cohort in Okinawa, Japan.

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.