Marked resistance of normal subjects to tube-feeding-induced diarrhea: the role of magnesium.

Abstract

Because it is often assumed that feeding formulas are responsible for the diarrhea that commonly occurs in tube‐fed patients, the authors of this report sought to test the tolerance in normal subjects of a commonly used enteral feeding formula. They reasoned that if normal persons can tolerate substantial volumes of feeding without diarrhea, it may be patient‐specific factors and not the formulas themselves that cause diarrhea in sick persons. After five healthy male volunteers had undergone a 72‐hour acclimation to oral Ensure Plus (Ross Laboratories, Columbus, OH), the investigators administered Osmolite HN (Ross Laboratories) by continuous duodenal infusion, at progressively increasing infusion rates, until the subjects could no longer tolerate it.The subjects were able to tolerate maximum infusion rates of between 198 and 340 mL/h (5000 to 8650 kcal/ d). In two subjects, the infusion was stopped for symptoms other than diarrhea (abdominal distention, bloating, heartburn, and headache in one, and abdominal distention with vomiting in the other). These subjects never developed diarrhea, defined as >300 g of stool per day, despite maximum infusion rates of 371 and 258 mL/ h. The diarrhea that developed in the other three subjects was modest (350 to 380 g/d) and occurred only at infusion rates exceeding 275 mL/h, or more than 400% of their estimated basal energy expenditures.Blood and stool samples were analyzed to elucidate the mechanisms causing the diarrhea. The magnesium content of pooled diarrheal stools was significantly greater than that of nondiarrheal stools, suggesting that the magnesium load (mean 89 mmol/24 h, or more than 6 times the typical intake for US men) may have been the causal factor. There was no evidence that unabsorbed fat, carbohydrate, or protein contributed to the diarrhea.