What is the most possible healthy food for my american pitbull terrier?

My APBT is 1 year and 3 month old and weigh about 50+lbs. I’ am currently feeding my pet iams dog food. I heard a lot of rumors that on the long run it’s really bad for my pet. So does any one have any recommendation on what kinder brand dog food is the most healthy without any added chemical and all that nasty gunk?