Iron is an essential mineral that primarily functions in the movement of oxygen from the environment to the tissues. There are two forms of dietary iron: heme and non-heme. Sources of heme iron include meat, fish and poultry. Sources of non-heme iron include beans, lentils, flours, cereals and grains. Iron levels are tightly regulated in the human body, mainly by controlling the amount of iron absorbed from food. The proportion of dietary iron absorbed is determined by the iron requirement of the individual; more iron present in the body means less iron is absorbed through the intestine. Heme iron is more easily absorbed than non-heme iron 1.
The risk of adverse effects from food sources of iron is low. The U.S. Food and Drug Administration (FDA) has established a Reference Daily Intake (RDI) of 18 mg iron for adults and children 4 or more years of age (21CFR101.9). RDIs are a set of dietary references for essential vitamins and minerals that are considered amounts sufficient to meet the daily requirements of healthy individuals. RDIs serve as the basis for calculating the percent daily value (%DV) amounts found on dietary supplement and food labels.