The Influence of Protein on the Absorption of Iron, Copper, and Zinc in Adult Women

Introduction: The distribution of iron in cellular materials has been studied extensively for about a century, whereas the biological significance of other trace minerals such as copper and zinc were considered of limited importance. During the earlier part of this century the important and essential role played by copper and zinc in animal metabolism came into focus. The three minerals are found in the blood components, as well as functioning as catalysts for many enzyme systems.

Recommended dietary allowances for iron have been established for men, women and children. Ingestion of suboptimal amounts of iron coupled with growth, pregnancy or menstrual loss can produce an anemia which is very prevalent throughout the world. Less research has been conducted on the dietary requirements for copper and zinc, as deficiency states produced by these minerals have not been established in man. Consumption of normal mixed diet will allow sufficient intake for absorption of these minerals to meet the demands of the body.

Absorption of these three minerals is very low, approximately 90 per cent being excreted in the feces. Various factors appear to influence the amount of iron, copper, and zinc absorbed. Recent investigations with animals indicate that protein and amino acids may form complexes with certain minerals to facilitate uptake and transport.

The purpose of the studies undertaken in this laboratory was to investigate the possible relationship of protein level and protein quality on the absorption of these minerals from natural diets. The two balance studies reported in this paper were part of a series of studies on college women. The protein levels of diets used were 35 g. and 48 g. but the protein sources were altered to furnish different ratios of animal to plant protein.