Iron found in the body is either actively in use or in storage. The amount of iron in storage varies with individual conditions and dietary intake. All human cells, including blood cells, contain iron. It is used to transport oxygen and produce energy. Iron deficiency is a common problem worldwide. Although it is present in many meats and plant foods, iron is not always effectively absorbed. Females especially can have issues with iron deficiency due to menstruation. Iron levels are greatly affected by nutrition.
Blood Levels of Iron
Normal iron blood levels of adult women are 30 to 126 ug/dL. Iron status is also noted by measuring hemoglobin and hematocrit levels; this is because iron is a major part of all blood cells. Blood levels of hemoglobin and hematocrit are often checked by a skin prick, which is less accurate than drawing levels from the vein. Other lab values used to check iron status include plasma ferritin and transferrin saturation.
Types of Iron
There are two types of iron: heme iron and nonheme iron. Heme iron is found in animal flesh and red meat in the diet when eaten. Heme iron is well absorbed into the body when eaten. Nonheme iron is found in plant foods and is not as well absorbed when eaten as heme iron. Metabolism mechanisms control iron absorption. In the typical American diet about 10 to 15 percent of total iron eaten from food is completely absorbed.
Regulation of Iron Stores
The amount of iron stored has a great effect on the ability to absorb iron. The lower the iron stores are, the more efficiently iron will be absorbed. For the average person, about 30 percent of the iron in the body is storage iron. Diets that are temporarily iron deficient can use storage iron to meet needs. The percentage of iron absorbed increases when there is a deficiency of iron intake. Excess intake of iron is difficult to remove. The body stores excess in the liver and bone marrow.
Stages in Life
During menstruation and pregnancy, females have increased need for iron. Females may lose too much iron during menstruation because there is iron in the blood. During pregnancy, iron needs increase due to increasing blood volume. Women on oral contraceptives lose less blood during menstruation and therefore lose less iron. According to the National Institutes of Health, females aged 9 to 13 need 8 mg iron per day, ages 14 to 18 need 15 mg/day, ages 19 to 50 need 18 mg/day and females older than 51 years need 8 mg/day. Pregnancy requires 27 mg iron per day, and lactation requires 9 to 10 mg iron per day.
Iron in the Diet
Sources of iron in food include red meat, enriched flour, spinach and soybeans. Iron in red meat is heme iron and therefore better absorbed. Nonheme iron in vegetables can have improved absorption if consumed with vitamin C. Iron supplements can be taken but occasionally result in side effects, such as constipation and gastrointestinal distress.