A solid supplement comprising the following components (A) and (B): (A) sphingomyelin in an amount of from 0.15 to 7% by mass; and (B) phosphatidyl inositol or a salt thereof, wherein the mass ratio of the content of phosphatidyl inositol or the salt thereof (B) in terms of phosphatidyl inositol content to the content of sphingomyelin (A) in the solid supplement, i.e., [(B)/(A)], is from 0.05 to 3.