Iron-deficiency anemia is the most prevalent type of anemia in North America. It can cause fatigue, weakness, headaches, and poor concentration. Particularly susceptible are women of child-bearing age and pregnant women, children, undernourished laborers, and the very poor. In children, deficiency can result in irreversible impairment of growth and cognitive development, emotional problems, and impaired immune function. Common problems with iron supplementation have included poor bioavailability, extensive inhibition by dietary components (most notably phytates), and gastrointestinal side effects. Iron chelated with the amino acid glycine is more highly absorbable and elicits greater clinical efficacy than other forms, while exhibiting minimal digestive discomfort.