Copper absorption and retention in pregnant women fed diets based on animal and plant proteins.

Copper absorption was determined by using 65Cu, a stable isotope of copper, in pregnant and nonpregnant women who were confined to a metabolic unit for 21 or 42 days. Absorption and retention of copper were determined from two diets. One diet was comprised primarily of animal protein sources and the other of plant protein sources. The percentage of absorbed copper from the animal protein diet was higher than from the plant protein diet. Copper absorption from the animal protein diet averaged 41.2 and 42.2% in nonpregnant and pregnant women, respectively. Copper absorption from the plant protein diet averaged 33.8% in nonpregnant women and 40.7% in pregnant women. The plant protein diet contained more copper and therefore the absolute amount absorbed was greater from the plant protein diet. The results suggest that either the level of dietary copper or a component of the diet may have an effect on copper absorption. Copper absorption from both diets tended to be higher in pregnant than in nonpregnant women, but the difference was significant only with the plant protein diet. The levels of copper fed in this study, 1.44 and 2.53 mg per day from the animal and plant protein diets, respectively, were sufficient to result in positive balance in all subjects. The amount of copper retained by pregnant women appeared adequate to provide for the increased requirements of pregnancy.