I agree about omega 3's and would advise to swap the cans of tuna for as many cans of wild salmon as you can afford.
Tinned tuna in brine has virtually all the omega 3 stripped out of it. If you can source it in olive oil that's better, but wild salmon is much higher in omega 3, and lower in mercury and other toxins.
Also worth considering swapping the tuna for canned mackeral or sardines in tomato or olive oil... if you don't those too fishy.
F 5 ft 3. HW: 196 lbs. Primal SW (May 2011): 182 lbs (42% BF)... W June '12: 160 lbs (29% BF) (UK size 12, US size 8). GW: ~24% BF - have ditched the scales til I fit into a pair of UK size 10 bootcut jeans. Currently aligning towards 'The Perfect Health Diet' having swapped some fat for potatoes.