Dogs can eat tuna occasionally but it shouldn’t form a daily part of your dog’s diet and there are better alternatives if you want to feed fish.
You also need to be careful about which tuna you feed.
Is tuna good for dogs?
Tuna is a highly nutritious food. It’s packed with protein, omega-3 fatty acids and vitamins.
Can dogs eat fish like tuna? Yes, in the sense that they won’t drop dead from the food itself.
However, that is only part of the story.
This post is for general informational and educational purposes only. I encourage readers to see my full disclaimer here.
The problem with tuna for dogs
The danger with tuna for dogs (and for humans) is that it does not live in pristine, unpolluted waters.
The ocean is an uncontrolled environment in far from optimal condition.
Unfortunately tuna, and all seafood, can be contaminated with:
- toxic heavy metals like mercury
- pesticides like DDT
- carcinogenic chemicals like PCBs
…just to name a few.
These toxins make their way into the ocean through industrial run-off into waterways and via atmospheric pollution from things like coal burning. (Natural processes like volcanic eruptions also spew mercury directly into the sea.)
The chemicals are absorbed by tiny organisms at the low end of the marine food chain and are passed along to the animals that eat them. Since mercury is not easily excreted it builds up in the tissues. By the time you reach the higher end of the food chain, fish like tuna can amass a lot of accumulated toxins. These toxins are passed along to your dog when he eats the tuna.
Tuna contains higher mercury levels than other seafood because it is a large and long-lived fish, one of the largest ocean predators. That means a lot of time to accumulate and store toxins.
And that’s not all..
Fish in dog food
If you’re considering feeding fish in dog food, there is the added risk of a potentially deadly additive called ethoxyquin, which is used to preserve the fat in fish meal.
Integrative vet Dr Karen Becker, whose own dog got ill from ethoxyquin, warns owners that the chemical is often added to the fish meal before it’s shipped to the pet food companies so they don’t have to name it as an ingredient. She says unless your pet food brand can specifically tell you it’s not in there, assume it is. She says this applies equally to leading “veterinary” brands of dog food.
Can dogs eat canned tuna?
Canned tuna will be better quality than fish meal in dog food, but it still carries the same contamination with heavy metals and ocean pollutants.
Mercury in most species of tuna exceeds the levels that would be safe enough to consume every day. Even people shouldn’t eat it that often.
According to Healthline, mercury impairs fine motor skills, memory and focus. It can lead to anxiety and depression and even cause brain cell death. The risk is high enough that pregnant or breastfeeding women and children are advised not to eat tuna. Mercury is also associated with endocrine disorders, reproductive problems and accelerated ageing.
If you’re determined to feed canned tuna, at least make sure it’s skipjack tuna (often this is the variety used in light tuna products and not albacore or yellowfin or bigeye, which contain many times more mercury.
All canned fish should be in spring water, never oil. Make sure the one you pick has no added salt and no flavorings.
Canned tuna, of course, is cooked. As with all meat, you’re better off feeding fish fresh and raw, as this is the way dogs are designed to eat.
Other good fish for dogs? Sardines
A safer option than feeding tuna to your dog is sardines, as pictured in the photograph at the top of this article.
These small oily fish don’t live long enough to store toxins in their bodies. Other suitable small fish include smelts, herring, mackerel and anchovies.
Sardines are a rich source of iodine which is thought to support thyroid health. They are also one of the few whole prey that most of us have ready access to. They contain edible bone which is an important part of your dog’s diet and, of course, the omega-3 fatty acids.
Can dogs eat sardines in oil?
No. If you’re feeding sardines from a can, make sure they’re plain and in spring water. But the best way to feed sardines is fresh and raw from the fishmonger.
I add a couple to Shiva’s meal every few weeks.
Vet Dr Peter Dobias has raised concerns about the possible presence of radioactive strontium in sardines.
He says strontium was released in large amounts from the scene of the Fukushima disaster in Japan. Japan is one of the largest sardine exporters in the world and a primary spawning site is right near the disaster site. Dr Tobias says canneries around world purchase from Japan and are not required to mark their sardines’ country of origin. He says there is the same problem of strontium in fish oils.
So again, choosing sardines fished from waters as far from Japan as possible and feeding even sardines sparingly seems wise.
Can dogs eat salmon?
Yes, but don’t feed farmed salmon because they have been exposed to lots of antibiotics to prevent disease. In addition, farmed fish are often fed GMO corn and soymeal-based diets. GMO salmon is also unlabelled as such, so the only way you can ensure it’s not GMO is to buy only wild-caught.
Can dogs eat canned salmon?
If you’re feeding a tinned fish, canned salmon from Alaska is said to be relatively lower in contaminants including mercury.
Can dogs eat raw salmon?
Yes. But according to Dogs Naturally Magazine, there is such a thing as salmon poisoning from a parasite typically found in Pacific salmon. They recommend freezing to kill this parasite.
But is it natural for dogs to eat fish?
Wolves have been observed catching fish in the wild to supplement their land-based prey. Check out these wolves in Northern Minnesota hunting freshwater fish.
Is fish oil good for dogs?
Fish oil comes with all the same risk of contamination as fish, and the added problem of being so highly unstable that it easily goes rancid.
Nowhere in nature do dogs encounter free oils. Despite the popularity of giving fish oil supplements to dogs, it’s far better to feed them in whole foods than as isolated chemistry.
In conclusion: Is tuna bad for dogs?
Tuna is higher in the toxic heavy metal mercury than most other fish. It also contains a range of other contaminants.
So the answer to can dogs eat tuna is yes, but there are safer seafood options, chief among them being sardines.
But feed even sardines only now and then, and be picky about the sardines you select.
If you never fed fish, your dog would not be missing much as long as you make sure the rest of his diet supplies a good amount of omega-3 fatty acids.