According to Dr. Ken Hilderbrand, longtime seafood technologist for Oregon State University, our salmon and tuna lose very little in the canning process, so it's nearly the same nutritional value as raw fish.  The value is locked in the can.  Be sure to save the juice that comes with the fish in the can.  There is a high percent of Omega-3 oil in that juice.
You want to pour away the liquid that comes with major brand tuna because it has no value.  The hydrolyzed vegetable protein will probably come up on you the rest of the day.
Mix the juice in a can of Oregon's Choice albacore or salmon with the fish or drink it, because it's good for you.