Nuts and Seeds. Another option for complementary proteins for legumes such as lentils is nuts or seeds. This complementary pairing is better than that of legumes and grains, as it provides you with more complete protein, but it isn't as common. Consider making a salad with both lentils and some type of nuts.You can use lentils in a Waldorf salad, for example, to make it a meal with complete protein.onsider making a salad with both lentils and some type of nuts. You can use lentils in a Waldorf salad, for example, to make it a meal with complete protein.