Insufficient intake or absorption of iron can cause iron deficiency anemia, a condition causing symptoms such as fatigue, weakness, difficulty maintaining body temperature and decreased immune function. Iron supplements can help prevent and treat iron deficiency. Iron supplements contain nonheme iron, a type of iron less easily absorbed by the body than heme iron, the type of iron found in meats. The body absorbs some iron supplements better than others.
Ferrous Iron Salts
Ferrous iron salts, including ferrous fumarate, ferrous sulfate and ferrous gluconate, provide the best absorbed iron supplements, according to the Office of Dietary Supplements. Ferrous fumarate has the highest percentage of elemental iron available for absorption, with 33 percent. Ferrous sulfate contains 20 percent elemental iron and ferrous gluconate contains 12 percent elemental iron.
Other Types
Some types of iron supplements may claim to cause fewer side effects than ferrous iron supplements, including those containing polysaccharide-iron complex. The body does not absorb iron as well from these products, however, notes MedlinePlus. Enteric coated and controlled-release iron supplements may cause fewer side effects, but the body does not absorb as much iron from these supplements, notes the Office of Dietary Supplements.
Taking Supplements With Food
The body absorbs the most iron when you take iron supplements on an empty stomach. Taking iron with food can decrease iron absorption by 40 to 50 percent, notes MedlinePlus. However, taking iron with food can help to reduce side effects such as nausea. If you do take iron with food, avoiding taking it with foods that inhibit iron absorption, such as calcium, high-fiber foods, coffee, tea or soybeans. Vitamin C supplements or vitamin C-rich food sources can promote better absorption of iron.
Side Effects
Therapeutic doses of iron used to treat iron deficiency often cause digestive side effects, including constipation, diarrhea, nausea, vomiting and dark stools. Taking iron in several divided doses throughout the day can help minimize side effects, advises the Office of Dietary Supplements.
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