Omega-3 fatty acids (EPA/DHA-enriched diets and fish oil)
One of the very few supplements with real randomized evidence behind it. Expect a modest improvement in mobility and, importantly, the possibility of getting the same pain control on a lower NSAID dose. It is not a replacement for pain medication.
Why this grade
Several independent randomized, double-blinded, controlled trials, including multicentre studies with over 100 dogs and one using objective force-plate weight-bearing as the endpoint, show consistent, modest benefit. It falls short of A because effect sizes are small relative to NSAIDs, several trials were manufacturer-funded, and the 2022 meta-analysis of nutraceuticals found the overall nutraceutical literature uneven even while treating omega-3s more favorably than most.
What the trials show
In a randomized, double-blinded, controlled trial of 38 client-owned dogs, food containing 3.5% fish oil omega-3s improved mean peak vertical force by 5.6% between day 0 and day 90, versus 0.4% in the control group. Peak vertical force is an objective force-plate measure of how much weight the dog is willing to put on the limb. A separate randomized, double-blinded, controlled trial across 18 veterinary clinics enrolled 127 client-owned dogs on a food with a 31-fold increase in total omega-3 content and a 34-fold reduction in the omega-6 to omega-3 ratio over six months. A third randomized, controlled, multisite trial at 33 veterinary hospitals with 131 client-owned dogs specifically examined whether omega-3 supplementation reduced the carprofen dose required. That is the most practically useful endpoint of the three, since NSAID dose reduction directly reduces long-term organ risk.
Harms and cautions
Well tolerated at typical doses. High doses can cause loose stool, fishy odor, and in theory altered platelet function, which matters if surgery is planned. Oil quality and rancidity are genuine concerns in unregulated supplements. Cod liver oil is a poor choice as a high-dose source because of vitamin A and D content.
Practical detail
- Route
- Therapeutic diet or oil/capsule supplement
- Typical course
- Ongoing; trials measured benefit at 90 days and beyond, so judge it at three months, not three weeks
- Monitoring
- Body condition score, since these are calorie-dense; tell your surgeon before any procedure
- Cost
- moderate
Regulatory status
- United States
- Sold as therapeutic diets and supplements; supplements are not held to drug-level manufacturing standards.
- Note
- Dose and EPA/DHA concentration vary enormously between products. A generic 'fish oil' capsule may deliver a fraction of the therapeutic-diet dose used in trials.
Questions worth asking your vet
- What actual EPA and DHA dose in milligrams should my dog get, rather than a number of capsules?
- Could adding this let us reduce the NSAID dose, and how would we test that safely?
- Is a therapeutic diet a better delivery route than capsules for my dog's calorie budget?
The evidence, one study at a time
Roush JK, Cross AR, Renberg WC, Dodd CE, Sixby KA, Fritsch DA, Allen TA, Jewell DE, Richardson DC, Leventhal PS, Hahn KA. Evaluation of the effects of dietary supplementation with fish oil omega-3 fatty acids on weight bearing in dogs with osteoarthritis. JAVMA, 2010;236(1):67-73.
rct 2010
The most persuasive entry because the endpoint is objective. Manufacturer-funded, and the effect is modest. But it is measured, not reported by hopeful owners.
- Design
- Randomized, double-blinded, controlled clinical trial
- Dogs analyzed
- 38
- Blinding
- double-blind
- Control
- Control food
- Duration
- 90 days
- Population
- 38 client-owned dogs with osteoarthritis at two university veterinary clinics
- Primary outcome
- Peak vertical force on force-plate gait analysis
- Result
- Mean peak vertical force improved 5.6% in the test-food group versus 0.4% in controls between days 0 and 90, significant for the test group only. 82% of test-food dogs showed improved weight bearing against 38% of controls.
- Funding
- Hill's Pet Nutrition
A multicenter study of the effect of dietary supplementation with fish oil omega-3 fatty acids on carprofen dosage in dogs with osteoarthritis. 2010.
rct 2010
The dose-sparing question is the clinically important one for geriatric dogs, since lower NSAID exposure means lower cumulative kidney and GI risk.
- Design
- Randomized, controlled, multisite (33 veterinary hospitals)
- Dogs analyzed
- 131
- Blinding
- double-blind
- Control
- Control food
- Duration
- Multi-month
- Population
- Client-owned dogs with stable chronic osteoarthritis
- Primary outcome
- Carprofen dosage requirement
- Result
- Examined whether omega-3 supplementation permitted reduced carprofen dosing.
- Funding
- Industry-supported
Multicenter veterinary practice assessment of the effects of omega-3 fatty acids on osteoarthritis in dogs. 2010.
rct 2010
Longer follow-up than most canine osteoarthritis trials, which typically stop at 28-90 days.
- Design
- Randomized, double-blinded, controlled
- Dogs analyzed
- 127
- Blinding
- double-blind
- Control
- Control food
- Duration
- 6 months
- Population
- Client-owned dogs with osteoarthritis across 18 clinics
- Primary outcome
- Owner- and veterinarian-assessed osteoarthritis signs
- Result
- Test food with a 31-fold higher total omega-3 content and 34-fold lower omega-6:omega-3 ratio was assessed over six months.
- Funding
- Industry-supported
Barbeau-Grégoire M, Otis C, Cournoyer A, Moreau M, Lussier B, Troncy E. A 2022 Systematic Review and Meta-Analysis of Enriched Therapeutic Diets and Nutraceuticals in Canine and Feline Osteoarthritis. International Journal of Molecular Sciences, 2022;23(18):10384.
meta analysis 2022
The single most useful reference for separating nutraceuticals that work from those that do not.
- Design
- Systematic review and meta-analysis. 1578 publications screened, 57 articles included, comprising 72 trials across nine categories of natural health compound.
- Blinding
- not-applicable
- Result
- Found omega-3-enriched diets among the better-supported nutritional interventions, in sharp contrast to chondroitin-glucosamine, which showed a marked non-effect.
- Funding
- Université de Montréal research groups (GREPAQ and CHUM arthrosis unit); see publication