Balances of calcium, magnesium and phosphorus in Japanese young adults.

This study was conducted to estimate the requirements of calcium (Ca), magnesium (Mg) and phosphorus (P) in Japanese young adults. From 1986 to 2000, 109 volunteers 123 males, 86 females), ranging from 18 to 28 y old, took part in mineral balance studies after written informed consent was obtained. The duration of the study periods ranged from 5 to 12 d, with 2-4 d 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 (A.A.) (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 correlated with Bal (r2 = 0.036, p = 0.048). The mean value and upper limit of the 95% confidence 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 correlated 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.