Fish Oil for Arthritis: What the Trials Show
Fish oil is one of the few joint supplements with good trial evidence in dogs. What two 2010 trials and a 2022 meta-analysis found, and the side effects.
Written by thecanineledger
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A 2022 meta-analysis concluded that “the use of omega-3 products beneficially modulates the painful condition of OA dogs and cats, while the intake of chondroitin-glucosamine has no analgesic effect.” (Barbeau-Grégoire et al., International Journal of Molecular Sciences 2022). OA is osteoarthritis.
While that makes fish oil one of the better-supported supplements, it isn’t free of risk, and the trials tested specific diets and products. This page sets out what the trials found and what the side effects can be.
1. What the meta-analysis found
Most trials were positive. “Regarding the efficacy of omega-3 products, only 2 [ 25 , 30 ] of the 20 trials on them were non-effective, which underlines the analgesic potential of these products.” Analgesic means pain-relieving.
Diets and supplements. The review found “an evident clinical analgesic efficacy for omega-3-enriched diets, omega-3 supplements and cannabidiol (to a lesser degree).”
Disclosure. The review had no direct funding. Its authors report working on osteoarthritis for several animal health companies.
→ Glucosamine and Chondroitin: The Meta-Analysis Says No
2. Two trials from 2010
In general practice. A randomised, double-blind trial enrolled “127 client-owned dogs with osteoarthritis in 1 or more joints from 18 privately owned veterinary clinics.” Dogs ate either a typical commercial food or a test food high in fish oil, for six months (Roush et al., Journal of the American Veterinary Medical Association 2010, abstract).
What owners saw. “According to owners, dogs fed the test food had a significantly improved ability to rise from a resting position and play at 6 weeks and improved ability to walk at 12 and 24 weeks, compared with control dogs.”
Measured on a force plate. A second trial in 38 dogs measured how much weight each dog put on its worst leg. “Improvement in peak vertical force values was evident in 82% of the dogs in the test-food group, compared with 38% of the dogs in the control-food group.” (Roush et al., Journal of the American Veterinary Medical Association 2010, abstract).
What they don’t show. Both trials tested one diet, not a fish oil capsule. The second trial’s authors say the benefit held was “At least in the short term”.
Our note: We read only the abstracts, which don’t state funding.
3. Possible side effects
A 2013 review. It lists “altered platelet function, gastrointestinal adverse effects, detrimental effects on wound healing, lipid peroxidation, potential for nutrient excess and toxin exposure, weight gain, altered immune function, effects on glycemic control and insulin sensitivity, and nutrient-drug interactions.” (Lenox and Bauer, Journal of Veterinary Internal Medicine 2013, abstract).
In plain terms. These include effects on blood clotting, stomach upsets, slower wound healing, the oil going off, extra calories and interactions with medicines.
What it doesn’t show. The review lists “potential” effects. The abstract doesn’t say how common they are.
Our note: We don’t know how common these side effects are. Tell your vet if your dog takes a blood thinner or is due for surgery.
4. What to think about
- Ask your vet about the amount. We don’t give one. It depends on your dog and the product.
- Count the calories. Extra weight makes arthritis worse.
- A diet or a supplement? The meta-analysis found benefit from both. The 2010 trials tested a diet.
- Give it time, and agree with your vet how you’ll judge whether it’s working.
Our note: These points are ours.
Our note: Fish oil can oxidise. We don’t cover how to check a product’s quality.
→ Arthritis Treatment: What Works, From Weight to Medication · → What Extra Weight Costs a Dog: The Labrador Lifetime Study
5. What we could not verify
| Commonly said | What we found |
|---|---|
| “Fish oil works for arthritis” | Supported for pain, in a 2022 meta-analysis. 18 of 20 omega-3 trials were positive. |
| “Any fish oil will do” | Not checked. The trials tested particular diets and products. |
| “It’s natural, so it’s safe” | No. A 2013 review lists several possible side effects. |
| “More is better” | Not checked. We don’t give amounts. The 2013 review lists nutrient excess as a risk. |
Sources
- Barbeau-Grégoire M, Otis C, Cournoyer A, et al. A 2022 Systematic Review and Meta-Analysis of Enriched Therapeutic Diets and Nutraceuticals in Canine and Feline Osteoarthritis. Int J Mol Sci 2022: systematic review and meta-analysis. No direct funding; authors report industry work
- Roush JK, Dodd CE, Fritsch DA, et al. Multicenter veterinary practice assessment of the effects of omega-3 fatty acids on osteoarthritis in dogs. J Am Vet Med Assoc 2010. ⚠️ abstract read. Randomised, double-blind trial, 127 dogs. Funding not checked
- Roush JK, Cross AR, Renberg WC, et al. Evaluation of the effects of dietary supplementation with fish oil omega-3 fatty acids on weight bearing in dogs with osteoarthritis. J Am Vet Med Assoc 2010. ⚠️ abstract read. Randomised, double-blind trial, 38 dogs. Funding not checked
- Lenox CE, Bauer JE. Potential adverse effects of omega-3 fatty acids in dogs and cats. J Vet Intern Med 2013. ⚠️ abstract read. Review
Always confirm with your vet before acting on anything on this page.