The human body needs iron for the production of enzymes and proteins, such as hemoglobin -- the protein in red blood cells that carries oxygen. Getting enough iron through dietary sources to meet the daily recommended intake, listed by the National Institutes of Health Food and Nutrition Board as 8 mg per day for adult males and post-menopausal women and 18 mg per day for adult women between 19 and 50 years old, can be difficult. Although spinach is an iron-rich food sources several factors make it less desirable as an iron supplement.
Types of Iron
Your body stores and reuses approximately 90 percent of its iron each day, therefore only excreting 10 percent, according to the National Institutes of Health Office of Dietary Supplements. To replenish the iron lost each day, many dietary sources contain iron. Iron exists in two different chemical structures; heme iron describes the type of iron derived from hemoglobin and therefore found in animal products while non-heme iron describes the chemical structure of iron found in plant-derived sources such as spinach.
Absorption
The ability of your body to absorb iron from food sources is influenced by many factors. As iron stores in the body become low, the body can absorb more iron. In addition, the human body absorbs heme iron more effectively, absorbing between 15 and 35 percent of the available iron. The body can only absorb 2 to 20 percent of the available iron in non-heme iron sources.
Iron in Spinach
One of the main drawbacks of relying in spinach to provide the daily recommended intake of iron is that the body fails to absorb much of the non-heme iron found in spinach. Therefore to get the same amount of iron into your blood as from a heme source, you must consume more of the spinach. One half cup of boiled spinach contains 3.2 mg of iron but the body will absorb less than 1 mg.
Oxalic Acid
Spinach also contains a chemical substance known as oxalic acid. Large amounts of oxalic, larger than one would generally consume eating foods containing oxalic acid, can be toxic. The main drawback of consuming oxalic acid is that it binds to metals, such as iron, therefore making the iron unavailable for the body to use.
Enhancing Iron Absorption
To take advantage of the iron provided by spinach, eat your spinach with foods that enhance iron absorption. Vitamin C and citrate, both found in citrus fruits, enhance the absorption of iron. Therefore eating spinach along with an orange can help counteract the presence of the oxalic acid. Proteins also increase the absorption of iron, making a healthy portion of meat or poultry a perfect pair for spinach.
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