Small Breed Dog Food: Why Kibble Size Matters

Tuna: The Pantry Staple That Needs Caution

I opened a can of tuna for my lunch and my dog appeared at my feet within seconds. The smell of tuna carries through an entire house and most dogs find it irresistible. I gave him a small piece and he looked at me like I had just handed him gold. But tuna is one of those foods where the details matter a lot. Feed the right kind in the right amount and it provides excellent nutrition. Feed the wrong kind too often and you risk mercury accumulation that can cause real health problems.

Tuna Nutrition for Dogs

Tuna is packed with protein and omega-3 fatty acids. A 100-gram serving of canned tuna packed in water contains approximately 115 calories, 26 grams of protein, less than 1 gram of fat, and zero carbohydrates. The protein content is excellent at 26 grams per serving, making it one of the highest protein-to-calorie ratios of any commonly available food. Tuna is also rich in selenium, vitamin D, and B vitamins. The selenium content is particularly notable because selenium binds to mercury in the body and can help reduce its toxic effects.

The omega-3 content of tuna varies by species. Albacore or white tuna has higher omega-3 content than skipjack or light tuna. A 100-gram serving of albacore tuna provides about 1.5 grams of EPA and DHA combined. Light tuna provides about 0.5 grams. However, albacore tuna also has higher mercury content because it is a larger, longer-lived fish. Skipjack tuna, the most common type in light canned tuna, is smaller and accumulates less mercury. This creates a tradeoff: more omega-3s but more mercury with albacore versus fewer omega-3s but less mercury with light tuna.

The Mercury Problem Explained

Mercury accumulates in fish through a process called biomagnification. Small fish eat tiny organisms that contain trace amounts of mercury. Larger fish eat those small fish and accumulate the mercury in their tissues. The largest and oldest predatory fish have the highest mercury levels. Tuna is a mid-level predator. It has more mercury than sardines or salmon but less than swordfish or shark. The concern for dogs is the same as for humans: chronic mercury exposure can cause neurological damage, kidney damage, and other health problems.

The FDA recommends that humans limit albacore tuna to one serving per week and light tuna to two to three servings per week. For dogs, the guidelines should be even more conservative because of their smaller body size. I recommend feeding tuna no more than once per week for medium and large dogs and no more than once every two weeks for small dogs. Choose light tuna over albacore to minimize mercury exposure. Canned skipjack tuna is the safest option with the lowest mercury levels.

Water vs Oil: Which Canned Tuna to Buy

Tuna packed in water is the only choice for dogs. Tuna packed in oil adds unnecessary calories and fat. A 100-gram serving of oil-packed tuna has about 200 calories compared to 115 calories for water-packed. The oil is usually soybean or vegetable oil, which provides no benefits for dogs. Some tuna is packed in olive oil, which is slightly better but still adds about 80 extra calories per serving. Always drain the water or oil from canned tuna before feeding it to your dog. The packing liquid often contains added sodium.

Low-sodium tuna is the best choice if available. Regular canned tuna can contain 200 to 400 milligrams of sodium per serving. For a small dog that needs only 200 to 300 milligrams of sodium per day total, one serving of regular tuna can exceed their entire daily requirement. Low-sodium tuna typically has 50 to 100 milligrams per serving, which is much more manageable. If you can only find regular tuna, rinse it under cold water in a fine-mesh strainer before feeding. This removes about 40 percent of the sodium.

Cooking Fresh Tuna for Your Dog

Fresh tuna steaks are safe for dogs when cooked thoroughly. Sear the tuna on both sides until the internal temperature reaches 145 degrees Fahrenheit. Do not serve tuna rare or raw. Raw tuna can contain parasites and bacteria just like raw salmon. The high protein content of fresh tuna makes it an excellent high-value training reward. Cut a cooked tuna steak into tiny cubes about the size of a pea. Each cube has about 3 to 4 calories. Freeze the cubes on a baking sheet and store in a freezer bag for training treats that last for weeks.

Alternatives to Tuna for Omega-3s

If you are concerned about mercury, several alternatives provide similar omega-3 benefits with lower mercury risk. Salmon provides excellent omega-3 content with much lower mercury levels. Canned wild salmon costs about the same as canned tuna. Sardines are an excellent alternative. They are small enough to have minimal mercury and are packed with omega-3s and calcium. A single sardine has about 25 calories and provides roughly the same omega-3 content as a serving of light tuna. Anchovies are similar to sardines with even lower mercury levels. Mackerel, specifically Atlantic mackerel, is another good option with high omega-3 content and low mercury. Avoid king mackerel which has high mercury levels.

The Bottom Line on Tuna

• Canned light skipjack tuna in water is the safest tuna option for dogs.
• Feed tuna no more than once per week for medium to large dogs.
• Small dogs should have tuna no more than once every two weeks.
• Albacore tuna has higher mercury. Choose light tuna instead.
• Drain and rinse canned tuna to reduce sodium content.
• Low-sodium tuna is preferable. Rinse regular tuna before feeding.
• Cook fresh tuna to 145 degrees. Never feed raw tuna.
• Tuna is high in protein. Excellent for high-value training rewards.
• One ounce of tuna is a reasonable portion for a 30-pound dog.
• Rotate tuna with salmon, sardines, and mackerel for variety and lower mercury risk.
• If your dog is a senior or has kidney concerns, choose a lower-mercury alternative.

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