Did you know that raw spinach contains oxalic acid, an organic substance that can interfere with the absorption of essential nutrients like calcium and iron? Oxalic acid binds with calcium, making it unavailable for use by our bodies. It also attaches to quite a few other vital nutrients, and long-term consumption of foods high in oxalic acid can lead to nutrient deficiencies. The good news is that oxalic acid is broken down upon heating, so there is no loss of nutrients in steamed or sautéed spinach.
Should you avoid raw spinach in your green drinks and salads? Is cooked spinach always the superior choice? Both fresh and cooked spinach contain about the same amount of macronutrients in a 100-gram serving (roughly 3 1/3 cups raw or 1/2 cup cooked spinach). Both servings are about 23 calories, 3.8 g of carbohydrates, 3 g of protein, 0.3 g of fat, and a whopping 2.4 g of fiber, which is 10 percent of the daily value.
Raw Spinach Benefits: There is no need to shun raw spinach simply because it contains oxalic acid. It is also rich in many essential nutrients, some of which are more available to our bodies when we consume them raw. These nutrients include folate, vitamin C, niacin, riboflavin, and potassium.
Cooked Spinach Benefits: When you eat spinach that has been heated, you will absorb higher levels of vitamins A and E, protein, fiber, zinc, thiamin, calcium, and iron. Important carotenoids, such as beta-carotene, lutein, and zeaxanthin, also become more absorbable.
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.