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...

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.

SummaryIn the previous analysis of our human mineral balance studies, we demonstrated positive correlations between the balances of calcium (Ca) and magnesium (Mg) and sodium (Na) intake in the range of 3.06 and 4.06 g/d or 43.71 and 96.40 mg/kg body weight (BW)/d, but there was no correlation between Na intake and Na balance. This suggested that the balances of Ca and Mg are affected by Na intake. Therefore, in the current study, we recalculated equilibrium intakes for Ca and Mg when balances of their intakes and outputs were equal to zero within the above Na range to reduce the effects of Na intake. When the balance was equal to zero, the mean value and upper limit of the 95% confidence interval for the regression equation between intake and balance were 4.078 and 4.287 mg/kg BW/d, respectively. Key Words equilibrium intakes of Ca, equilibrium intakes of Mg, adequate Na intake, human balance study It is generally believed that there are three levels of dietary intake of a nutrient: excess, adequate and deficit. The border between excess and adequate is recognized as the upper limit, while the other border between adequate and deficit is termed the requirement.To determine an upper limit and a requirement for a nutrient, it is necessary to understand the scientific evidence indicating quantitative information about the dietary intake and the signs and symptoms of excess or deficit of the nutrient.For the minerals (sodium [Na], potassium [K], calcium [Ca], magnesium [Mg] and phosphorus [P]), whose signs and symptoms of deficit or excess are poor, the determination of the requirement and the upper limit is difficult because of the absence of evidence.In such cases, the equilibrium intakes (EI) to keep balances of nutrients zero as results of balance studies, are the sole sources of information available to determine the dietary reference intakes (DRIs). However, this value is not equal to the estimated average intake (EAR) in DRIs, but a value in adequate intakes.In order to estimate the equilibrium intakes (EI) of the above-mentioned minerals, we conducted 11 human mineral balance studies ( 1-9 ). In the previous analysis for Ca, Mg and P, we demonstrated positive correlations between the intake and balance for Ca and P, but failed to do so for Mg ( 5 , 6 ). We demonstrated, however, positive correlations between Mg intake and balance of both Ca and P, which gave the equilibrium intakes (EI) for Mg ( 7 ).On the other hand, in the previous analysis for Na and K, we also demonstrated positive correlations between the intake and balance for Na and K. However, correlation between the intake and balance for Na turned to be not significant when omitting data of two experiments whose Na intake were 2.21 g/d (the lowest Na intake and negative Na balance study) ( 1 ) and 6.87 g/d (the highest Na intake and the positive Na balance study) ( 2 ). So, we considered the range of Na intakes in the remaining nine experiments to be adequate or within the range between the requirement and the upper limit.In addition, we already ...

SummaryThe present study sought to determine estimated equilibrated dietary intakes (EEDIs) for nine essential minerals: sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P), iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn), using data from 17 human mineral balance studies conducted from 1986 to 2007 (subjects ϭ 178). Among these studies, two used male subjects, two subjected some or all subjects to sodium restriction, and one study utilized a low protein diet; these subjects were not included in the present analysis. Consequently, data from 13 studies of young female subjects ( n ϭ 131) consuming a standard diet were selected. Balance distribution medians for six of the minerals (Na, K, Mg, Fe, Zn and Cu) were positive, so the data were adjusted to set the medians of the balances to zero. Medians for the other minerals (Ca, P and Mn) were close to zero and were not adjusted. Intake and balance for each mineral were divided by body weight (BW), lean body mass (LBM), and standard body weight (SBW), which was calculated using height and standard body mass index (BMI ϭ 22), and EEDIs were calculated as the intercept of a simple regression equation. When relationships between intake and balance of a mineral were not significant in the regression equation, a significant regression equation comparing intake and balance of another mineral was used to calculate the intercept. Significant simple regression equations were not obtained from any of the three parameters of Na or Zn, or for two of the parameters of P; thus, K, Fe and Ca balances were used to determine the intercepts for Na, Zn and P, respectively. EEDIs for the minerals were: Na (67.9, 89.0, 62.5), K (39.5, 53.5, 37.4), Ca (11.0, 14.4, 10.1), Mg (4.18, 5.51, 3.86), P (18.7, 24.6,17.3) (mg/ kg BW/d, mg/kg LBM/d, mg/kg SBW/d), Fe (180, 237, 165), Zn (168, 241, 166), Cu (30.9, 42.6, 29.7), Mn (55.1, 72.1, 50.7) ( g/kg BW/d, g/kg LBM/d, g/kg SBW/d), respectively. These values are nearly identical to the mean dietary intakes.