Let your husband prepare two types A and B.
Let him feed you in this order for 20 days
A B A B A B A B A B A B A B A B A B A B
Let him feed your son in this order for 20 days
B A B A B A B A B A B A B A B A B A B A
(Neitehr your son nor you know the sequence you take)

You and your son write down assessment on each day.

AT teh conclusion of the study, compare assessment between A and B.