No, lentils are good for gut health, as well as lowering blood sugar and fighting heart disease. Because lentils are a source of prebiotic fiber, which is the type your gut bacteria prefers, they can help improve gut health. Americans don't get enough fiber in our diets, which is what our guts need and 1/2 cup of lentils provides 8 grams of fiber, a quarter of our daily needs. (source)