One of the most abundant metals on Earth, iron is essential to most life forms. Every cell in the body contains iron, and it’s needed for all bodily functions. About three-quarters of the body’s iron is contained in the red blood cells as hemoglobin, which carries oxygen from the lungs to all parts of the body. Approximately 5 percent of our iron is found in myoglobin, a form of hemoglobin in muscles. Hemoglobin and myoglobin pump oxygen to the cells with the help of iron.

In addition to oxygenating the blood and cells, iron supports energy production. It also plays a key role in maintaining many functions of the immune system. Iron is abundant in the liver and spleen, where it’s used to make red blood cells.

Food Sources For Iron

Dietary iron takes two forms: heme and nonheme. Heme iron, derived from hemoglobin, is found in animal foods that once contained hemoglobin, such as red meat, fish, and poultry. Nonheme iron is found in plant foods, such as lentils, beans, dark leafy greens, bananas, grapes, and sesame seeds. Although nonheme iron isn’t as easily absorbed as heme iron, vitamin C enhances its absorbability. So if you’re having a spinach salad, boost its C content with some tomato or orange slices.

What About Supplements?

Iron is difficult to get from dietary sources, which is why the World Health Organization calls iron deficiency the number one nutritional disorder worldwide. Iron deficiency may also result from blood loss, ulcers, excessive coffee or tea consumption, or poor digestion. People who don’t absorb iron normally because of gastrointestinal disorders are also at risk for iron deficiency. In some cases, vitamin B6 or B12 deficiency may be the underlying cause. Symptoms of iron deficiency include anemia (where the number of red blood cells or the amount of hemoglobin in the cells is low), brittle hair, dizziness, fatigue, hair loss, nervousness, pallor, and slowed mental reactions.

Certain stages of life, including periods of growth and pregnancy, may require supplemental iron. Be sure to talk to your healthcare provider before you take iron supplements, however. Too much iron may damage your liver and pancreas, and some studies suggest that high iron levels may increase the risk of heart disease.

Balance is key—the body has a highly effective mechanism that prevents iron overload, but when a deficiency occurs, the body does not increase its absorption rate enough to prevent anemia. Talk to your doctor to find out if your iron level is balanced or if you could benefit from a supplement.