Forbidden by: gluten-free (with some exceptions) and paleo diets
Whole grains contain compounds called phytates, which can bind to minerals such as zinc, iron, and manganese, preventing our bodies from absorbing these nutrients, according to Cassie Bjork, a Minnesota-based registered dietitian. “Phytates make whole grains less nutrient-dense than a nutrition facts panel would let you believe,” she says. “In my opinion whole grains aren’t necessary at all. They don’t contain any vitamins and minerals you can’t get from non-starchy fruits and vegetables.”
But while phytates and other “antinutrients” can interfere with absorption, they don’t completely strip a food of its beneficial parts, says Andrea Giancoli, R.D., a spokesperson for the American Academy of Nutrition and Dietetics. And unless you’re really loading up on produce, you’re going to miss out on a lot of belly-filling, heart-friendly fiber, adds Bonnie Taub-Dix, R.D., author of Read It Before You Eat It. Plus those without celiac disease or gluten intolerance won’t reap any dietary benefits from giving up grains that contain wheat gluten and in fact could become deficient in B vitamins, studies have found.
If you are concerned about phytates, buy sprouted grains or soak yours before cooking, Giancoli says, but most people don’t need to worry.