Are All Carbohydrates Interchangeable? Protein

Though neither grains nor starchy vegetables are considered a major protein source, the protein quality in potatoes, a starchy vegetable, is notably higher than the protein quality of grains, comparable in quality (as measured by "biological value") to the protein in egg and milk. And though food choices from both groups can help add fiber to the diet, grains offer unique nutritional benefits as well, typically offering more thiamin, zinc and vitamin E.