Insufficient intake or absorption of iron can cause iron deficiency anemia, a condition characterized by a lack of healthy red blood cells. Without sufficient iron, the body cannot produce hemoglobin, a protein in red blood cells that carries oxygen to the body's organs and tissues. Iron deficiency anemia causes symptoms of fatigue and weakness. Iron supplements used to treat and prevent iron deficiency may cause unpleasant gastrointestinal side effects.
Absorption
The gastrointestinal tract absorbs only a small percentage of iron consumed. The body can absorb 15 to 35 percent of heme iron from animal-based foods, but only 2 to 20 percent of nonheme iron from plant-based foods and supplements. Food components such as tannins in black and green tea, calcium in dairy products and phytates in legumes and whole grains and proteins found in soybeans can decrease the body's absorption of nonheme iron, notes the Office of Dietary Supplements. The body absorbs most iron in the small intestines. Gastrointestinal disorders affecting the small intestines, such as Crohn's disease, may hinder iron absorption.
Gastrointestinal Side Effects
Iron supplements can cause a variety of gastrointestinal side effects, including upset stomach, nausea, vomiting, constipation and diarrhea or dark-colored stools. Delayed-release iron supplements may cause fewer side effects, but the body absorbs less iron from these supplements.
Minimizing Side Effects
While taking iron supplements on an empty stomach promotes better absorption, taking them with food may help to minimize side effects. Avoid taking iron supplements with dairy products, coffee, tea or cereals, as substances in these foods can hinder the body's absorption of iron. Dividing supplemental iron into several smaller doses can also help minimize side effects, notes the Office of Dietary Supplements.
Warning
High doses of iron can cause potentially fatal iron poisoning. Iron poisoning causes stomach and intestinal problems and may lead to liver failure and low blood pressure. Children are especially vulnerable to iron poisoning. Contact a poison control center immediately if you suspect an adult or child you know has taken too much iron.
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