Answer:
Glittering points that downward thrust. Sparkling spears that never rust.
What is eaten but not grown and was born in water but will disappear if soaked?
What contains zero calories, but if you consume it, you will probably gain weight?
We are five little objects of an everyday sort. You will find us all in a tennis court.
Only two backbones and thousands of ribs.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.