Answer:
I am the minerals vital for your good health.
I am always coming but I never arrive. What am I?
I am black and white. I have strings I have keys. I make sound without my lips. I make dough with no flour
The more you take the more you leave behind. What am I?
Everyone has me and no one can lose me. What am I?
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.