Fish Oil
Also known as: salmon oil, sardine oil, anchovy oil
The most reliable food-based source of the anti-inflammatory omega-3s EPA and DHA.
What it actually is
Oil pressed from cold-water fish — salmon, sardines, anchovies, or menhaden. Sold as a supplement or included in kibble/fresh food.
Why it's used in dog food
Dogs cannot make EPA and DHA efficiently from plant sources. Fish oil delivers them directly. Effects: reduced joint inflammation, softer coat, healthier skin, and supported brain function.
A bit of history
Cod liver oil has been given to working dogs since the 1800s. Modern purified fish oils (molecularly distilled to remove mercury and PCBs) came to pet supplements in the 1990s.
Pros
- •Best-studied natural anti-inflammatory for dogs
- •Proven benefit for arthritis, allergies, and cognitive decline in seniors
- •Improves coat and skin quality within 4–6 weeks
- •Small daily dose has an outsized effect
Cons
- •Oxidizes quickly — must be refrigerated and used within 60–90 days of opening
- •Cheap fish oils are often rancid on arrival; a sharp fishy smell means throw it out
- •Too much can thin blood and cause loose stools
Safety notes
Dose is typically 100–150 mg combined EPA+DHA per 4.5 kg (10 lb) of body weight per day. Overdose can affect clotting. Do not give with anticoagulant medications without vet advice.
Sourcing & quality
Look for molecularly distilled, IFOS-certified, or third-party tested products. Sardine/anchovy oils are lower on the food chain and lower in mercury than salmon.
Commonly found in
Skip this if…
Your dog is on blood thinners or has a bleeding disorder.
The verdict
One of the highest-value supplements you can add. Just don't buy a cheap rancid one.