You ask if it is true Sister White recommended that we not mix several cereals in the same dish. I am not aware of any such councel from her pen. In the book, 'Counsels on Diet and Foods,' you will find a statement from Ellen White's pen on page 321 concerning the making of bread. She states:
"All wheat flour is not best for a continuous diet. A mixture of wheat, oatmeal and rye would be more nutritious than the wheat with the nutrifying properties separated from it."
I can be seen from this statement that she recommended the mixing of grains in bread making, and if this was so in the making od bread, I can see no objections to their being used in a cereal dish. ALW