Can i do a procedure that every times a player eat 20 times an item he dies

yes,

make a global variable with numbers

do when item eaten , add 1 to global variable

check if global variable > 19 , if yes

then kill entity or deal damage like 1000

for the kill entity procedure, you can do: 

"deal [max health of event/target entity] damage to [event/target entity] type: [any damage type]"

and it would work just fine. but this, unlike dealing a limited amount of damage, would still kill the player even if their health is higher than usual.