What Is Phytic Acid? Some People Are Freaking Out About the "Antinutrient" Are these fears really legit? Phytic acid is a substance found in seeds, nuts, grains, and legumes It's known in some circles as an "antinutrient" because it binds to minerals like magnesium, iron, and zinc, thus preventing your digestive tract from absorbing them But is phytic acid really that bad? Beans tend to get a bad rap. If it’s not school kids associating them with farts, it’s health bloggers freaking out over the fact that beans contain phytic acid, a substance that is also found in grains, nuts, and legumes which is commonly labeled an “anti-nutrient.”