SummaryThis study was conducted to estimate the requirements of sodium (Na) and potassium (K) in Japanese young adults. From 1986 to 2000,109 volunteers (23 males, 86 females), ranging from 18 to 28y old, took part in 11 mineral balance studies after written informed consent had been obtained. The duration of the study periods ranged from 5 to 12d, with a 2-4d adaptation period. Foodstuffs used in each study were selected from those commercially available. The Na and K content of the diet, feces, urine and sweat were mea sured by atomic absorption spectrophotometer. The results of a study in which Na intake was 6.87g/d (ca. 300mmol/d), the highest of all the studies, showed apparent positive Na balances. In contrast, another study in which Na intake was 2.21g/d (ca. 100mmol/d), the lowest of all the studies, showed apparent negative Na balances. These two studies seemed to differ from the other studies, as shown by regression equations calculated from either data of all the studies (n=109) or data that did not include the two studies (n=90). The dietary intakes of Na and K ranged between 38.56-142.23 and 26.77-74.42mg/kg body weight (BW)/d, or 2.21-6.87 and 1.83-3.61g/d, respectively in the complete data, and 43.71 -96.40 and 26.77-63.70mg/kg BW/d, or 3.06-4.06 and 1.83-2.68g/d, respectively in the data that did not include the two studies. The intakes of the two minerals were positively cor related. Na intake (Intake) was correlated positively with apparent absorption (AA) of Na, which was also correlated with Na urinary output (Urine). In the data that did not include the two studies, Na balance (Balance) was not correlated significantly with either Na Intake (r2=0.005) or AA of Na (r2=0.006). However, analysis of all the data showed a significant correlation between Na Balance and both Na Intake (r2=0.361) and AA of Na (r2=0.360). In the complete data, the mean value and upper and lower limits of the 95% confidence interval for the regression equation between Intake and Balance for Na, when balance was equal to zero (i.e mean, upper and lower limits), were 55.824, 60.787 and 50.862mg/ kg BW/d, respectively. K Intake was correlated positively with AA of K, which was also cor related with both Urine K and K Balance. There was a significant correlation between K Intake and K Balance in both the complete data (r2=0.213) and the data that did not include the two studies (r2=0.116). In all the cases, mean, upper and lower limits for K were 39.161, 41.782 and 36.540mg/kg BW/d, respectively. Intakes of Na and K did not corre late with their respective AA rates (%). Within the ranges of K Intake in this study, K Bal ance was affected markedly by K Intake itself as well as by Na Intake. However, in the case of Na, when the data of the highest and lowest Na intake studies were excluded from the analysis, Na Balance did not correlate with Na Intake, whereas the data of all the studies showed Na Balance was affected strongly by Na Intake. The data of this study allowed the estimated average requirements (EARs) for both mi...

SummaryThis study was conducted to estimate the requirements of calcium (Ca), mag nesium (Mg) and phosphorus (P) in Japanese young adults. From 1986 to 2000, 109 vol unteers (23 males, 86 females), ranging from 18 to 28y old, took part in mineral balance studies after written informed consent was obtained. The duration of the study periods ranged from 5 to 12d, with 2-4d of adaptation. Foodstuffs used in each study were selected from those commercially available. The minerals present in diet, feces, urine and sweat were measured by atomic absorption spectrophotometer (Ca, Mg) or spectrophotometer (P). The dietary intakes of Ca, Mg and P ranged from 4.83-23.58, 2.44-7.83 and 13.46-45.69 mg/ kg BW/d, respectively. Dietary intake (Intake) of Ca was positively correlated to apparent absorption (AA.) (r2=0.425), which was also correlated with urine excretion (Urine) (r2=0.327) and balance (Bal) (r2=0.382). Intake of Ca was slightly but significantly corre lated with Bal (r2=0.036, p=0.048). The mean value and upper limit of the 95% confi dence interval for the regression equation between Intake and Bal when balance is equal to zero (Mean and upper limit) for Ca were 11.752 and 12.555 mg/kg BW/d, respectively. Intake of Mg was positively correlated to A.A. (r2=0.451), which was also correlated with Urine (r2=0.486) and Bal (r2=0.349). However, Intake of Mg was not correlated with Bal. Intake of P was positively correlated with A.A. (r2=0.959), which was also correlated with both Urine (r2=0.908) and Bal (r2=0.135). Intake of P was slightly but significantly corre lated with Bal (r2=0.103, p=0.0013). Mean and upper limits for P were 22.584 and 24.059 mg/kg BW/d, respectively. Intakes of Mg and P correlated negatively with their respective A.A, rates (%) (r2=0.120 for Mg, r2=0.109 for P). However, there was not much of a correlation for Ca. Balance of Ca was positively correlated with that of Mg (r2=0.541), but not with that of P.

Summary Background: The origin of moisture in diarrhea feces is unknown but may represent the unabsorbed part of intestinal contents or alternatively, body fluid excreted into the digestive canal. If the latter mechanism contributes to moisture in the feces, active transport of water (H 2 O) associated with ion exchange channels may be involved. Objective: To investigate this possibility we measured the content of moisture and minerals (sodium [Na] [Mn]) in feces collected during a 12-d metabolic study on 11 young Japanese female students. Design: The study was carried out as part of a human mineral balance study. The same quantity of food was supplied to each of the subjects throughout the study without consideration of body weight. Fecal specimens were collected throughout the study and were separated into those originating from the diet during the balance period based on the appearance of the ingested colored marker in the feces. Results: The moisture content of the feces ranged between 53 and 92%. Na content in the feces was low and stable when the moisture content was below 80%, whereas it increased up to serum levels when the moisture content increased above 80%. On the other hand, K content increased when compared to dry matter base. However, when comparing concentration/g moisture, K content increased when moisture was below 70%, but decreased when this rose above 70%.

SummaryThe content of calcium (Ca) and magnesium (Mg) in sweat during exercise is considerably higher during a relatively low intake of sodium (Na) of 100mmol/d than with an intake of 170 mmol/d. For this reason and also because Ca and Mg have a negative bal ance with a Na intake of 100 mmol/d, we analyzed the relationship between Na intake and balances of Ca and Mg in data from 11 balance studies. From 1986 to 2000, 109 volunteers (23 males, 86 females) with an age range of 18 to 28 y took part in mineral balance studies. The balance periods ranged from 5 to 12 d. In a given experiment, the diet of each subject contained the same quantity of food, although this varied between experiments, and was supplied during the balance period without consideration of body weight. In the data of all the studies (n=109), the balances of Ca and Mg did not correlate positively with Na intake. However, when the data of the highest Na study were excluded, the balances of Ca and Mg correlated positively with Na Intake. The mean value for the regression equation between Na intake and Ca and Mg balances when the respective balance was equal to zero were, 63.308 mg Na/kg BW/d (Ca: n=96, r2=0.134) and 60.977 mg Na/kg BW/d (Mg: n=96, r2=0.268), respectively. These values are considerably higher than Na requirements esti mated by inevitable Na loss. Low dietary Na may therefore be a risk factor for maintaining positive balances of Ca and Mg.

Using these correlations, the mean value and upper limit of the 95% confidence interval (from the regression equation between Mg intake and either the balances of Ca or that of P, when each balance is equal to zero) were 4.584 and 4.802 (against Ca balance), 4.554 and 4.785 (against P balance) mg/kg BW/d, respectively. Balances of Mg and Ca correlated with each other.