Estimation of sodium and potassium intakes assessed by two 24 h urine collections in healthy Japanese adults: a nationwide study

Abstract

Excess Na intake and insufficient K intake are well-known risk factors for CVD. International comparative studies have reported that Japan has the highest intake of Na and the lowest intake of K in the world. However, no recent study has precisely assessed Na and K intakes in Japanese adults. In the present study, Na and K intakes were estimated from two 24 h urine collections implemented in twenty-three out of forty-seven prefectures in Japan. Apparently healthy men (n 384) and women (n 376), aged 20 to 69 years, who had been working in welfare facilities were recruited, with data collection conducted in February and March 2013. The mean Na excretion was 206·0 mmol/d in men and 173·9 mmol/d in women. The respective values of K excretion were 51·6 and 47·2 mmol/d. The excretion of both Na and K varied considerably among the prefectures, and was higher in subjects with a higher BMI. In contrast, only K excretion was associated with age. After estimating the usual intakes of Na and K, it was found that none of the male subjects met the recommended Na intake values of the WHO, and that only 3·2 % met those of the Japanese government. The respective values for females were 0·1 and 5·0 %. For K intake, 7·5 % of the total subjects met the recommended values of the WHO and 21·7 % met those of the Japanese government. These findings suggest that there is an urgent need for the development of an effective intervention programme to reduce Na intake and promote K intake in the Japanese population.Key words: Sodium: Potassium: Intake: Japanese adults Recently, the WHO (1,2) published new guidelines for recommended intake levels of Na and K in adults and children. However, most people consume more Na and less K than these recommended values worldwide (3 -5) . Excess Na intake leads to hypertension that is associated with severe adverse health outcomes such as CHD and stroke, and the beneficial effect of salt reduction on these diseases has been confirmed (6,7) . Salt reduction is also a cost-effective means of reducing the risk of CVD (8,9) . Excess Na intake and insufficient K intake independently lead to hypertension and other CVD (10,11) , and higher K intake reduces blood pressure in individuals with hypertension (10,11) .The INTERSALT (3) and INTERMAP studies (5) have reported that Na intake is higher in the East Asian countries of China, the Republic of Korea, and Japan than in other countries. Substantial differences in intake have also been reported between northern and southern China and within Japan (3,5) . Moreover, K intake has been reported to be lower in these East Asian countries than elsewhere (3,5) . Nevertheless, the National Health and Nutrition Survey in Japan reported that Na intake is being continuously decreasing (12) . The reason for this trend is attributed to the Westernisation of the Japanese diet and change in food preservation method, i.e. the change from preservation with salt to the use of home refrigerators. Average Na and K intakes in the 2011 survey were 4287 mg/d (186·4 mmol/d) and...

Sodium sources in the Japanese diet: difference between generations and sexes

“…Although we previously reported that higher BMI was associated with higher Na excretion (i.e. absolute amount of Na intake) (11) , the source of Na in the present study was the same regardless of body constitution. On the other hand, higher BMI was marginally associated with a lower proportion of discretionary Na intake in women on multivariate analysis.…”

“…Details of the collection method have been reported elsewhere (11) . One mmol of Na is equal to approximately 58·5 mg of salt (NaCl).…”

Iodine Excretion in 24-hour Urine Collection and Its Dietary Determinants in Healthy Japanese Adults

“…Details of the study have been reported elsewhere. 21 Briefly, 10 dietitians working at 10 different welfare facilities in each of the 20 areas participated as research dietitians. The 20 study areas were selected based on geographical location and the feasibility of recruitment of research dieticians.…”

“…Details of the collection method have been reported elsewhere. 21 Briefly, participants set the starting time of collection and then discarded the first urine at the starting time. All subsequent specimens were collected until the same time as the starting time on the next day.…”

“…Samples with a ratio of <60% or >140% were excluded ( n = 72), as described previously. 21 In addition, participants with missing data ( n = 4) or a history of thyroid disease were excluded ( n = 2). However, participants taking diuretics or with a history of renal dysfunction were not excluded because participants were workers and were assumed to be sufficiently healthy to work.…”