Interannual study of spot urine–evaluated sodium excretion in young Japanese women

Abstract

The authors investigated interannual differences in the sodium excretion levels of young healthy Japanese women as estimated from spot urine analysis at Nakamura Gakuen University from 1995 to 2015. Participants included 4931 women aged 18 to 20 years who were classified into three time periods according to year of health check:first (1995-2001), second (2002-2007), and third (2008-2015). Estimated daily urinary sodium and potassium excretion levels and the sodium to potassium ratio were 120.6±31.9 mmol, 35.2±8.1 mmol, and 3.5±0.9, respectively. Adjusted for body weight, sodium excretion, and potassium excretion significantly decreased in the second and third period compared with the first period (P<.001). Systolic blood pressure also decreased in the same way between time periods (P<.001). Estimated urinary excretion levels of sodium and potassium in young Japanese women have decreased over the past 20 years independently of body weight. | INTRODUCTIONExcess sodium intake plays an important role in the development and progression of hypertension and the development of cardiovascular diseases.1-3 It has been reported that excess sodium intake from early stages of life contributes to population increases in blood pressure (BP), hypertension, and prehypertension. 4 Estimations of the mortality rates resulting from reductions in salt intake as a function of age suggest a greater attenuation of mortality rates for younger people. 5These reports suggest that reducing salt intake from a younger age is an important lifestyle modification when it comes to prophylactic and therapeutic issues of hypertension. Large-scale trends in sodium intake during recent decades have not yet been reported for young Japanese people. The Japanese National Health and Nutrition Survey provides information on interannual changes in the sodium intake of Japanese people. According to this survey, the sodium intake of young people has decreased during the past 20 years, but sodium intake corrected for energy intake was relatively unchanged during the past 10 years. 6,7 However, this survey has several limitations. For instance, the proportion of young people in the population surveyed was small, and sodium intake was calculated as a function of food consumed by a family and position in the family (eg, 35% intake for the father, 25%intake for the mother, and 40% intake for two children), 8 and thus the investigation underestimates the actual amount of diet. 9,10 Notably, the results of a salt intake study of 760 Japanese people aged 20 to 69 years with 24-hour urinary sodium excretion measurements taken at two time points differ from Japanese National Health and Nutrition Survey results, raising the question of whether salt intake did decline across these decades. 8 To better determine recent trends in the sodium intake of Japanese people, we need to evaluate changes in urinary sodium excretion levels and compare these values with the sodium intakes recorded by the Japanese National Health and Nutrition

A self‐monitoring urinary salt excretion level measurement device for educating young women about salt reduction: A parallel randomized trial involving two groups

“…Japan is among the countries with the highest salt intake in the world, and since this dietary behavior is formed since adolescence, it is necessary to establish salt management and a practical salt‐reduction education tool for young individuals. The present study was the first to report that frequent self‐monitoring using a self‐monitoring salt excretion level measurement device can improve 24‐hour urinary sodium/potassium ratio.…”

“…According to a national study on daily salt intake among 1043 Japanese women aged 18‐22 years, the mean values of salt intake based on 24‐hour urine collection and a dietary questionnaire were 9.8 g and 9.2 g, respectively, which substantially exceeded the Japanese target salt‐intake value of 7.0 g . We also reported that the mean estimated daily salt‐intake value for female university students (mean age of 17.9 years) who entered university from 1995 to 2015 was 8.1 g, and that only 31.3% of the students consumed more salt than the Japanese target value of 7.0 g . A study estimating the decrease in the mortality rate by reducing salt intake showed that the earlier the age at which salt restriction was started, the more effective it was in decreasing the mortality rate .…”

“…that the mean estimated daily salt-intake value for female university students (mean age of 17.9 years) who entered university from 1995 to 2015 was 8.1 g, and that only 31.3% of the students 10 consumed more salt than the Japanese target value of 7.0 g. 9 A study estimating the decrease in the mortality rate by reducing salt intake showed that the earlier the age at which salt restriction was started, the more effective it was in decreasing the mortality rate. 11 These reports suggest that promoting the commencement of salt reduction at a younger age in Japan, where excessive salt is consumed, is an important factor in motivating lifestyle changes to prevent and treat hypertension.…”

Sodium intake, sodium excretion, and cardiovascular risk: involvement of genetic, hormonal, and epigenetic factors

“…The most important message of the study by Yasutake and colleagues is that Japanese women attending the Department of Nutritional Sciences at Nakamura‐Gakuen University have reduced their sodium intake during the past 20 years. It was noted, however, that these women were likely more motivated, as they were a faculty involved in nutrition, and that women in other faculties might be less interested in health and therefore consumed more salt.…”

“…Yasutake and colleagues have published an interesting study on the interannual changes in the sodium excretion levels, as estimated from spot urine, of young healthy Japanese women. The authors have reported a significant reduction in urinary sodium excretion during the past 20 years, independent of body weight and consistent with a gradual decline in sodium intake.…”