Iron 411: Both raw and cooked spinach are excellent sources of iron, containing twice as much as other leafy greens. A 100-gram serving of raw spinach contains 2.71 mg of iron, whereas cooked spinach contains 3.57 mg. Keep in mind that iron absorption is influenced by how much iron you already have in your body and by other nutrients that you eat with your meals. For instance, vitamin C facilitates iron absorption, while other substances like tannins and polyphenols inhibit iron absorption—so the amount of iron we absorb will vary regardless of whether or not spinach is cooked.
As with other vegetables, there are pros and cons to both raw and cooked forms. Eating a wide variety of plant foods is important for good health, and eating plant foods in both raw and cooked form will provide you with the richest array of nutrients.
Remember to look for fresh spinach that is bright green and appears freshly picked; spinach that is older and paler in color has been shown to contain lower concentrations of nutrients