Whole grain flours (e.g., barley, brown rice, buckwheat, whole wheat) were characterized and their effects on the retardation of starch digestion in pastes and cakes were examined. Buckwheat flour had the highest dietary fiber, the lowest starch, and lowered paste viscosities than all other flours. Under in vitro starch digestion, buckwheat and whole wheat flours were highly effective at lowering starch hydrolysis in pastes and cakes. Furthermore, replacing wheat flour with 50% buckwheat or whole wheat flours maintained the volume index and textural properties of cakes. Therefore, substituting up to 50% of whole grain flour for wheat flour in cake formulation produces acceptable quality as well as health benefits (lower predicted glycemic index and increased nutritional value).