Researchers in Peru fed toasted amaranth flour, popped amaranth grain, and amaranth flakes to young children as the source of all dietary protein and fat, and as 50% of their daily energy requirements.  Later, children were fed a mix of amaranth and corn in various flour, flake, and meal forms.  Results showed that protein uptake from amaranth flour was favorable, and combining amaranth with corn provided for better protein uptake than consuming corn alone.
The Journal of Nutrition, January 1988; 118(1):78-85