Quinoa is a naturally gluten-free whole grain that is a good source of plant protein and fiber. Quinoa is safe to be eaten by people who have celiac disease and/or gluten intolerant. Unlike some plant proteins, quinoa is a complete protein, meaning that it contains all nine essential amino acids that our bodies cannot make on their own. One cooked cup provides about 8 grams of protein and 5 grams of fiber.