What are some baby foods that i can give my 5 month old to poop more?

My son poops every 4 to 5 days and that is not good i want to give him foods that would make him poop more..i give him prune juice with water once in a while and i don't want to use like baby laxative or anything like that i want him to poop natural..so please help..thank you guys..=)