Buckwheat flour is made from ground groats and has a robust taste that works well for baked goods like quick breads. It is gluten free, making it appropriate for those with celiac disease to use in baking.
Buckwheat flour has similar properties to whole wheat flour, so using it in place of buckwheat flour in recipes is a good substitute. All-purpose flour can be substituted for buckwheat flour.
Quinoa is an ancient grain high in protein, and quinoa flour is a creamy, off-white color. The darker the color, the less processing it is. Quinoa flour can be used cup for cup in recipes calling for buckwheat.
Soy flour is processed from dehulled soybeans, and comes in three varieties: full fat, low fat and fat free. The full fat variety is a good substitute for buckwheat flour. Since soy flour packs down in storage, stir it well before measuring.