Iron deficiency is the most common nutrient deficiency in the world. Three levels of iron deficiency are generally identified (3):
- Iron stores are depleted, but the functional iron supply is not limited.
- The supply of iron is low enough to impair red blood cell formation, but not low enough to cause measurable anemia.
- There is inadequate iron to support normal red blood cell formation, resulting in anemia.
Individuals at increased risk of iron deficiency include:
- Infants and children between the ages of 6 months and 4 years due to the rapid growth rates sustained during this period (4).
- Early adolescence is another period of rapid growth. In females, the blood loss that occurs with menstruation results in additional iron requirement (4).
- In pregnant women, the developing fetus and placenta as well as blood volume expansion, increase the iron requirement (4).
- Individuals with chronic blood loss (e.g., intestinal parasitic infection) (1).
- People who donate blood frequently, especially menstruating women, may need to increase their iron intake to prevent deficiency (1).
- Individuals with celiac disease, an autoimmune disorder.
- Individuals with Helicobacter pylori infection (24).
- Individuals who have had gastric bypass surgery may suffer from poor absorption of iron from food.
- People consuming only vegetarian diets, because iron from plant sources is less efficiently absorbed than that from animal sources (11).
- Individuals who engage in regular intense endurance training, which may be due to increased microscopic bleeding from the gastrointestinal tract or increased fragility and rupture ('hemolysis') of red blood cells (11).
Most of the symptoms of iron deficiency are a result of the associated anemia, and may include fatigue, rapid heart rate, and rapid breathing on exertion.
Iron deficiency also impairs the ability to maintain a normal body temperature on exposure to cold.
Severe iron deficiency anemia may result in brittle and spoon-shaped nails, sores at the corners of the mouth, and a sore tongue. In some cases, advanced iron-deficiency anemia may cause difficulty in swallowing due to the formation of webs of tissue in the throat and gullet (25).