Twister from Janet

My friend Janet post a twister and when I read it I remember that the words she post was our motto in school when I was in primary. I and Jenny discussed about the answer until I remember it, but I will not tell it yet because you will guess it too-so I´ll be waiting. Think....think..think now

below is the twister:

What is it???
we have it when we were born
and we will die with it
the poor has it, the rich need it
and if you eat it you will die!