Does the Oxalic Acid in Spinach Inhibit the Absorption of Iron?

The term “nutrient-dense food” perfectly describes spinach, which has few calories per serving but is rich in many nutrients, including iron. However, as with iron from all plant sources, the iron in spinach is present as non-heme iron. This form of iron is not absorbed as efficiently as heme iron, the iron found in meat and animal sources. Additionally, the oxalic acid in spinach binds with iron, which further inhibits iron absorption. You can improve the absorption of iron from spinach by eating it with foods that enhance iron absorption.

Iron Content of Spinach

According to the USDA National Nutrient Database, 100 grams of raw spinach contains 2.71 milligrams of iron, whereas the same amount of boiled spinach contains 3.57 milligrams of iron 1. Adult men, 19 to 50 years, require 8 milligrams of iron daily, while menstruating women aged 19 to 50 years need 18 milligrams of iron daily. Part of these needs can be met by eating spinach. However, the University Health Center of the University of Georgia recommends that vegetarian women may need to eat 33 milligrams of iron daily, because of less iron being absorbed from plant foods 4.

Oxalic Acid in Spinach

Oxalic acid content in vegetables varies from 0.1 to 1.7 grams per 100 grams of the vegetable. According to the USDA Agricultural Research Services, 100 grams of spinach contains about 1 gram of oxalic acid 3. Because the high content of oxalic acid combines with iron and reduces its bioavailability, the Center for Disease Control and Prevention states that eating spinach with foods that contain a high amount of vitamin C improves the absorption of iron.

Increasing Iron Absorption

In addition to consuming vitamin-C-rich fruits such as:

  • oranges
  • grapefruits
  • strawberries
  • cantaloupes to enhance iron absorption from spinach
  • you can plan your meals to include meat
  • fish or poultry along with spinach

These sources of heme-iron-rich food improve the absorption of non-heme iron from spinach.

Other Nutrients in Spinach

Apart from iron, spinach is rich in other minerals such as calcium, manganese, magnesium and potassium. Additionally, spinach contains flavonoid compounds that promote health.