Iron is an important mineral that plays a role in many essential functions. Women, during years of menstruation, require more iron than men: 18 mg versus 8 mg for males. After menopause, this amount decreases to 8 mg for women. About two-thirds of the iron in the body is found in a protein called hemoglobin, while the remaining amounts are tied to myoglobin or other proteins. Iron's primary function is to transport oxygen, but it is also involved in some biochemical reactions. While you can usually get enough iron from your diet, some sources are better than others.
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Heme vs. Nonheme Iron
Iron exists in two forms: heme and nonheme. Heme iron, derived from hemoglobin, comes from animal foods. Nonheme iron, which sticks to myoglobin, comes from plant sources, explains the Office of Dietary Supplements. Chicken, beef, oysters and turkey are all rich in heme iron, which is more easily absorbed and utilized by your body. Spinach, as well as oatmeal, beans and tofu, are rich in nonheme iron. While this type of iron is still beneficial, your body doesn't use it as efficiently.
Functions of Iron
Heme iron from hemoglobin helps deliver oxygen to tissues and organs. Nonheme iron from myoglobin works to carry oxygen to muscles. Since spinach only provides nonheme iron, one drawback is that you may be depriving your tissues and organs of the iron needed for basic functions. Iron is also essential to regulate cell growth and aid in cell differentiation. Getting only nonheme iron from spinach in your diet may lead to problems with cell growth.
Another drawback of relying on only spinach as an iron supplement is that it can cause a form of iron deficiency, known as anemia, since it only provides heme iron. When the iron stores in your body are depleted, you have pale skin, feel weak and have a compromised immune system. This deficiency can occur from inadequate intake of iron-rich foods, excessive bleeding or from poor absorption. To avoid a deficiency, include foods with heme iron in your diet.
Eating a variety of iron-rich foods, including spinach, is only effective if you consume the right types of foods in your diet. Foods high in vitamin C, such as strawberries, oranges, broccoli and red peppers, help your body absorb iron. Caffeinated beverages can cause your digestive system to rapidly excrete iron before it gets a chance to absorb it. If spinach is a primary source of iron for you, do not have coffee, tea or cola while you eat it. Calcium also affects how efficiently your body absorbs iron. Spinach provides calcium, in addition to iron. Your body may not effectively use the iron in spinach, since the calcium may counteract its absorption.