Should You Be Concerned About Oxalates in Leafy Greens?
Putting fear about antinutrients into perspective
If you are taking good care of your brain, some of these foods probably make it into your weekly rotation: beans, berries, beets, coffee, cranberries, chocolate, coffee, leafy greens, nuts, sweet potatoes, tea, tofu, oranges, and whole grains. These brain-healthy foods provide abundant nutrients like fiber, flavonoids, vitamins, and minerals. Dark leafy greens, especially, have been repeatedly shown to be a key component of a brain healthy diet, reducing Alzheimer's risk in this study, and beta-amyloid plaque in the brain in this one. Adding additional leafy greens to the Mediterranean diet yielded remarkable brain gains in the Green MED Diet study.
But you may also have read that these foods contain antinutrients—substances that prevent those beneficial nutrients from being absorbed. Common antinutrients include oxalate (also called oxalic acid), lectins, tannins, phytates, and phytoestrogens. Some even call these foods “toxic” because of their antinutrient content.
How can foods be both good for your brain and toxic? Well, they can’t. The confusion stems from throwing the word toxic around as it pertains to plant foods. While antinutrients may pose some minor disadvantages, calling them toxic is a wild exaggeration. The truth about antinutrients is more nuanced—and much more interesting—than that. But first, it helps to understand what antinutrients are and what they do.
Think of Antinutrients as the Plant’s Defenders
Antinutrients like oxalate are naturally occurring substances in plants. Many serve as a defense mechanism against anything that could harm a plant, such as insects, fungi, and parasites. In the process of defending the plant, they interfere with absorption of key nutrients, mostly calcium, iron, potassium, magnesium, and zinc. When you consume these plants, their natural defense systems kick in, binding up minerals and vitamins which keeps them from getting absorbed.