Itadakimasu

when we watch anime ora drama in japan, ussualy we hear a phrase "itadakimasu" at every meal time every day. but what is the meaning of "itadakimasu" exactly. and then i try to I look up the word in my dictionary, and try to search this phrases really means.
it was said that "itadakimasu" means I take your life. i began to think, why this phrases said when they had meal? my friend that study in faculty of Japanesse letter, he said that "itadakimasu" is a reward or symbol to animals, plants, and for people that have work to make (grow/catch) our meals (farmers, fisherman, or breeder). Shinto religion, was have a powerfull effect in this phrases, that we have to honour every life and work that sacrified for us.

itadakimasu :