Magnesium absorption and metabolism in patients with chronic renal failure and in patients with normal renal function

Abstract

The intestinal absorption of magnesium was determined under strictly controlled dietary conditions in patients with chronic renal disease and in patients with normal renal function. The average net absorption of magnesium of patients with chronic renal failure was significantly lower (17% of magnesium intake) than the absorption of patients with normal renal function (48.5%). The lower absorption of magnesium of patients with chronic renal failure was due to the significantly higher fecal magnesium excretion, averaging 82.5% of the magnesium intake, compared with an average of 51.5% for patients with normal renal function. The fecal/urinary magnesium excretion ratio for patients with normal renal function was close to 1.0, whereas it averaged 1.75 for patients with chronic renal failure, which indicates a shift of the magnesium excretion from the kidney to the intestine. The magnesium balance did not differ significantly from that of age-matched patients with normal kidney function receiving a similar or higher magnesium intake. In a long-term study of a patient with chronic renal failure, the net absorption of magnesium was greater during a higher magnesium intake than during the lower magnesium intake; however, the magnesium absorption was only half the value, 24% vs. 48%, for patients with normal renal function receiving the same magnesium intake. Increasing the calcium intake from 200 to 800, 1400, and 2000 mg/day did not change the magnesium balance or the net absorption of magnesium of patients with chronic renal failure and of patients with normal renal function.