Why is it risky?
Canned tuna intended for human consumption carries several specific risks when fed regularly. First: tuna is high in unsaturated fats and low in vitamin E, chronic feeding causes steatitis (yellow fat disease), a painful inflammatory condition. Second: tuna contains bioaccumulated mercury from the marine food chain, raising concerns with habitual feeding. Third: tuna contains thiaminase (destroyed largely by canning heat, but relevant to raw tuna). Fourth: some cats develop exclusive tuna preference and refuse balanced food.
Affected Systems
Digestive · Nervous
Symptoms
Steatitis: hypersensitivity to touch along the back, reluctance to move, weight loss, depression. Thiamine deficiency (raw tuna or excessive amounts): incoordination, seizures, cardiac abnormalities.
What To Do
No action for occasional exposure. If a cat has been fed tuna exclusively for weeks: vet visit and bloodwork.
Notes
Tuna formulated as cat food (Applaws, quality brand tuna varieties) is balanced to compensate for these deficiencies and is safer than human-grade canned tuna as a regular food. If using human-grade: choose skipjack in water (lower mercury than albacore/white tuna). Never use tuna in brine, the sodium content is harmful to cats.
Sources
→ Cornell Feline Health Center — vet.cornell.edu
→ VCA Animal Hospitals — vcahospitals.com