Also called · EPA · DHA · n-3 · fish oil
What it is
Omega-3 is a class of fatty acid. The third carbon from the end of the chain carries a double bond, which is why it is written n-3, commonly ω3.
Three of them matter nutritionally. α-linolenic acid (ALA) comes from perilla and flaxseed oil; EPA and DHA come from fish oil.
Once NRC (2006) and AAFCO (2016) recognised EPA and DHA as essential nutrients, adding fish oil to pet food became standard practice.
What it does
It changes what inflammation is built from
The body builds signalling molecules called eicosanoids out of the fatty acids in its cell membranes. The ones derived from arachidonic acid, an omega-6, push toward more inflammation. Raise omega-3 and that raw material is substituted, which changes how hard the inflammatory response swings.
Joints — slowing the rate cartilage breaks down
Osteoarthrosis feeds on itself: MMPs (matrix metalloproteinases) start digesting healthy cartilage along with the damaged part. ω3 has been shown to inhibit the arachidonic acid cascade and suppress MMP release, breaking that loop. It is why joint therapeutic diets lean on EPA for dogs and DHA for cats.
A study where painkiller doses dropped
Dogs with osteoarthritis fed a fish oil rich in ω3 performed daily activities better and required lower doses of non-steroidal anti-inflammatory drugs. (Fritsch et al., JAVMA 236(5), 2010)
Heart — suppressing cytokines at the cachexia stage
In dogs with chronic heart failure, particularly cases that had progressed to cardiac cachexia, feeding ω3 from fish oil was shown to suppress activation of cytokines such as TNF and IL-1.
Brain — membrane fluidity
DHA is involved in maintaining cell membrane fluidity and has been linked closely to canine cognitive dysfunction syndrome (CDS) and, in humans, to Alzheimer’s disease.
How to feed it
For cats there is no settled figure for how much ω3 to add. This one calls for caution.
It is a fat, so mixing it into a meal helps absorption. If you are feeding it for joints or skin, allow at least 4–8 weeks before judging the effect.
What to watch for
Fish oil is polyunsaturated, so it oxidises into lipid peroxides easily and burns through vitamin E. Every extra 1 g of fish oil per kg of food requires roughly 10 IU more vitamin E. Raising omega-3 alone actually erodes antioxidant defence.
One study observed reduced platelet function and prolonged bleeding time in cats fed a diet supplemented with high-concentration ω3.
Fish oil is a low-melting-point unsaturated fat and oxidises quickly. Stored badly after opening, what you are actually feeding is oxidised fat.
Common questions
α-linolenic acid (ALA) is a precursor to EPA and DHA, but the conversion is inefficient. Real pet foods use fish oil as the main source, with perilla or flaxseed oil as a supporting ingredient at best.
Joints and skin need the fatty acid composition of cell membranes to change, which usually takes 4–8 weeks or more. Two weeks is not long enough to judge.
Concerns this ingredient relates to
General nutrition information. It does not replace a diagnosis or a prescription. If your animal has a medical condition or is on medication, talk to your veterinarian first.