When people say fish oil can be good for joint health, they are referring to the fact that fish, as well as some other plant-based oils, contain omega-three fatty acids. So what are they, and how can they help?

What are they?

Omega-3 fats are a key family of polyunsaturated fats. Omega-3 fatty acids include:

  • Alpha-linolenic acid (ALA)
  • Eicosapentaenoic acid (EPA)
  • Docosahexaenoic acid (DHA)

EPA and DHA come mainly from fish/ marine based sources, ALA is found in vegetable oils and nuts.

ALA can be considered an “essential” fatty acid; essential fatty acids are those the body cannot make in sufficient amounts, and they must be provided through diet. Several of ALAs derivatives such as EPA and DHA have important metabolic consequences. EPA and DHA can be synthesised or made from ALA. However, as the conversion process is inefficient in dogs and nearly nonexistent in cats both these omega-3s can be beneficial to add to pets’ food.

Amounts of omega-3s in diets

If a diet is ‘complete’ then omega-3s are likely already added. However FEDIAF guidelines do not recommend any minimum for ALA, DHA or EPA apart from in growth and development guidelines. 

In therapeutic diets and in diets especially made for joint disease and joint health then they will also be added at higher levels. Target ranges for EPA and DHA vary quite widely for different conditions, but typically fall between 50 and 220 mg/kg body weight.

Inflammatory diseases and osteoarthritis

Supplementing omega-threes may be considered to support a pet as part of an arthritis management plan should the owner be keen to try. They should NOT be used instead of pain relief and anti-inflammatory medication if your dog is experiencing chronic pain.

Omega-3 fatty acids have been highlighted as the only nutraceutical with a sound evidence base supporting its use in companion animals. Studies suggest that omega-threes have anti-inflammatory properties in many species and can be used to help manage osteoarthritis. Supplementation has been shown to have an effect on OA in pet dogs; resulting in improved weight bearing (and thus probably less pain – Ed.). There is evidence to support their use and recent studies have shown statistically significant, if mild, improvement in owner perception of comfort and mobility.

Inflammation involves a multitude of cell types, chemical mediators and interactions. These fatty acids are capable of partly inhibiting many aspects of inflammation; and there are many mechanisms underlying the anti-inflammatory actions of EPA and DHA.

Potential adverse effects

As with any substance, dietary supplements, or nutraceuticals, omega-3 fatty acids have the potential for adverse effects. Omega-3s have many listed benefits and can certainly be considered in the management of several conditions; these are however potential risks associated with usage of omega-3 fatty acids.

Adverse effects, if observed, are likely to be dose dependent. Important potential adverse effects of omega-3 fatty acid supplementation including gastrointestinal effects and weight gain. To achieve the higher concentrations of omega-threes seen in some arthritis studies our pets would need to eat LOTS of oily fish. As you can imagine that can cause issues so that is why it may be better to buy them in supplement form as a capsule, oil or tablet.

The National Research Council publication on Nutrient Requirements of Dogs and Cats indicates a safe upper limit of the combined amounts of EPA + DHA as 370 mg per (kg body weight) for dogs. Presently, not enough published data are available to set a safe upper limit for cats.


Omega-three fatty acids may certainly help as part of an arthritis management plan. However if your dog is overweight one of the best ways you can help is to get them to lose weight to a healthy body condition. This has been shown to improve lameness in dogs. So, you must be very careful if you supplement with omega-threes that you are not doing so in a way that causes weight gain. There are many supplements out there; it is important to ask your veterinary team for advice as they all contain different amounts of EPA and DHA.

If done well and correctly, using a good quality omega-three supplementation could certainly be beneficial as one part of the jigsaw puzzle to management of arthritis. Remember that other important things are medication prescribed by your vet, weight loss if required, other therapies, changes in exercise routine and home adaptations. NB: Remember that cod liver oil is NOT the same as fish oil for omega-three supplementation. Excessive use of cod liver oil can lead to hypervitaminosis A in pets.

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