
Insufficient iron leads a lower level of red blood cells. Pre-menopausal women lose iron through menstruation, they need 15 mg of iron a day, and men require 10 mg of iron a day.
The typical American diet provides 5 to 6 mg of iron for every 1000 calories consumed. Since many women eat fewer than 2000 calories a day, it can be difficult for them to meet their iron needs. Therefore iron supplement are often prescribed by women.