Magnesium balances and plasma and blood cell concentrations were determined in 34 men and women, 20 to 53 yr of age, during each season for 1 yr while they were consuming their customary diets. Dietary records were maintained 365 days. Analysis of variance indicated no seasonal variation in intake or balance. Blood cell magnesium correlated with magnesium intake (r2 = 0.203; p less than 0.04). Daily magnesium intakes of the men (323 mg) were significantly higher (p less than 0.01) than of the women (234 mg), and reflected greater calorie consumption for their greater body weights. Daily magnesium balances for the men and women were -32 and -25 mg, respectively. Multiple regression analysis showed that magnesium balance was associated not only with magnesium intake but also with the intake of other nutrients such as fiber, protein, calcium, and phosphorus. Moreover, the effect of these nutrients on magnesium balance varied with age and sex.

Metabolic calcium and phosphorus balances, blood calcium and phosphorus levels, and alkaline phosphatase activity of 34 men and women, 20 to 53 yr of age, were determined each season during 1 yr while consuming customary diets. Dietary records were maintained 365 days. Analysis of variance indicated that serum Ca, P, and alkaline phosphatase levels were affected by season (p less than 0.0001), whereas calcium or phosphorus intakes were not. Calcium and phosphorus intakes of the men (1075 and 1533 mg, respectively) were higher (p less than 0.01) than of the women (695 and 1095 mg, respectively), but balances were not statistically different between them. Daily calcium balances for the men and women for the year were -81 and -85 mg, respectively; daily phosphorus balances were -239 and -130 mg, respectively. Stepwise regression analysis indicated that dietary calcium and protein were significantly associated with calcium and phosphorus balances, but in opposite directions, and only in women over 35 yr of age.