Lentils are good for your health! Black Lentils are high in fiber and complex carbohydrates, and they are a great vegetarian protein substitute. Even better, they are easy to cook. A half-cup of dry lentils can produce over a cup of cooked lentils. Each serving contains about 9 grams of protein and 80 percent of your daily fiber needs. This makes lentils an excellent choice for people on a gluten-free diet.