Fish oil

Fish oil, EPA and DHA explained, with dog arthritis research, limits of the evidence and questions to ask before choosing a supplement.

Ingredient Directory›Fish oil

Ingredient & nutrient profile

Fish oil

A source of marine omega-3 fatty acids. Look beyond the words “fish oil” to the amounts of EPA and DHA and the evidence for the intended use.

Fat and OilDogCat
Ω3
Fish oilNutritional role • Research • Practical context
SpeciesDogs and cats
ScopeIngredient and nutrient context
AssessmentInitial evidence summary
Sources checked23 September 2026
Nutritional role

What it contributes

Fish oil is a mixture of fats, rather than a single active substance. EPA and DHA are the long-chain omega-3 fatty acids commonly discussed in clinical nutrition. The amount of oil in a capsule or food does not, by itself, tell you how much of either fatty acid it supplies.

Species and formulation

Read it in context

This profile is relevant to both dogs and cats, but the linked arthritis trial tested dogs only. Its findings should not be presented as evidence that the same product or dose treats arthritis in cats. Tufts clinical guidance also discusses fish oil in selected heart patients, with veterinary oversight. [2]

Research

What the evidence shows

Roush and colleagues conducted a randomised, double-blinded trial involving 38 dogs with osteoarthritis. Dogs received a fish-oil-enriched food or a control food for 90 days; the enriched-food group had improved weight bearing. This supports the tested dietary approach, not every fish-oil supplement or every joint-health claim. Our study entry now includes a full-text appraisal, with participant flow, direct comparisons and funding checked. [1]

Limits and safety

Before changing the diet

Discuss supplementation with your vet, particularly if your pet has a bleeding disorder or already eats a diet high in omega-3 fatty acids. Product concentration and quality vary. More oil is not automatically more beneficial, and a study of a formulated food does not provide a universal supplement dose. [2]

Food labels

Questions worth asking

Ask for EPA and DHA amounts per daily serving, the source of the oil, storage instructions and quality-control information. Count what the existing food supplies before considering an additional supplement.

Connected evidence

Explore the study

Study links follow your species selection. A shared nutrient profile may discuss more than one species.

Dogs • Controlled trial • Full-text appraisalFish-oil-enriched food and weight bearing in dogs with arthritisRead the study summary, methods and limitations.
Sources

References and review scope

  1. Roush et al. (2010), original study
  2. Tufts University: heart disease and nutrition, fish-oil guidance

This is an initial, source-linked overview, not a systematic review or a product endorsement. FEDIAF is the European pet-food industry federation; its guidelines provide formulation context rather than an independent clinical trial. Study-specific access limitations are stated above.

Fish oil or fish protein hydrolysate?

These are different ingredients. Fish oil is the fat fraction; a protein hydrolysate contains protein-derived fragments. Read the fish protein hydrolysate profile for preparation differences and the limits of the canine behaviour evidence.

Research on this ingredient

We have not completed a research review for this ingredient. This does not indicate that it is ineffective or unsafe.

Products listing or mentioning this ingredient

88 products linked through reviewed ingredient occurrences from manufacturer declarations or partial editorial summaries. Whole-label verification may remain pending. An ingredient’s presence alone does not establish a nutritional outcome.

  • ROYAL CANIN® Digestive Care ROYAL CANIN® Digestive Care - ROYAL CANIN® Digestive Care; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Giant Adult ROYAL CANIN® Giant Adult - ROYAL CANIN® Giant Adult; United Kingdom; manufacturer declaration Dog; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Hair & Skin Care ROYAL CANIN® Hair & Skin Care - ROYAL CANIN® Hair & Skin Care; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Hairball Care ROYAL CANIN® Hairball Care - ROYAL CANIN® Hairball Care; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Indoor Appetite Control ROYAL CANIN® Indoor Appetite Control - ROYAL CANIN® Indoor Appetite Control; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Indoor Long Hair ROYAL CANIN® Indoor Long Hair - ROYAL CANIN® Indoor Long Hair; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Labrador Retriever Puppy ROYAL CANIN® Labrador Retriever Puppy - ROYAL CANIN® Labrador Retriever Puppy; United Kingdom; manufacturer declaration Dog; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Light Weight Care ROYAL CANIN® Light Weight Care - ROYAL CANIN® Light Weight Care; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Maine Coon Adult ROYAL CANIN® Maine Coon Adult - ROYAL CANIN® Maine Coon Adult; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Maine Coon Kitten ROYAL CANIN® Maine Coon Kitten - ROYAL CANIN® Maine Coon Kitten; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Maxi Puppy ROYAL CANIN® Maxi Puppy - ROYAL CANIN® Maxi Puppy; United Kingdom; manufacturer declaration Dog; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Medium Ageing 10+ ROYAL CANIN® Medium Ageing 10+ - ROYAL CANIN® Medium Ageing 10+; United Kingdom; manufacturer declaration Dog; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Medium Sterilised ROYAL CANIN® Medium Sterilised - ROYAL CANIN® Medium Sterilised; United Kingdom; manufacturer declaration Dog; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Mini Sterilised ROYAL CANIN® Mini Sterilised - ROYAL CANIN® Mini Sterilised; United Kingdom; manufacturer declaration Dog; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Mother & Babycat ROYAL CANIN® Mother & Babycat - ROYAL CANIN® Mother & Babycat; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Norwegian Forest Cat Adult ROYAL CANIN® Norwegian Forest Cat Adult - ROYAL CANIN® Norwegian Forest Cat Adult; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Outdoor ROYAL CANIN® Outdoor - ROYAL CANIN® Outdoor; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Persian Adult ROYAL CANIN® Persian Adult - ROYAL CANIN® Persian Adult; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Persian Kitten ROYAL CANIN® Persian Kitten - ROYAL CANIN® Persian Kitten; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Poodle Adult ROYAL CANIN® Poodle Adult - ROYAL CANIN® Poodle Adult; United Kingdom; manufacturer declaration Dog; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Pug Adult ROYAL CANIN® Pug Adult - ROYAL CANIN® Pug Adult; United Kingdom; manufacturer declaration Dog; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Ragdoll Adult ROYAL CANIN® Ragdoll Adult - ROYAL CANIN® Ragdoll Adult; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Sensible 33 ROYAL CANIN® Sensible 33 - ROYAL CANIN® Sensible 33; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Siamese Adult ROYAL CANIN® Siamese Adult - ROYAL CANIN® Siamese Adult; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Sphynx Adult ROYAL CANIN® Sphynx Adult - ROYAL CANIN® Sphynx Adult; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® Urinary Care ROYAL CANIN® Urinary Care - ROYAL CANIN® Urinary Care; United Kingdom; manufacturer declaration Cat; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® X-Small Adult ROYAL CANIN® X-Small Adult - ROYAL CANIN® X-Small Adult; United Kingdom; manufacturer declaration Dog; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • ROYAL CANIN® X-Small Puppy ROYAL CANIN® X-Small Puppy - ROYAL CANIN® X-Small Puppy; United Kingdom; manufacturer declaration Dog; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Saki-Hikari Balance Saki-Hikari Balance, editorial ingredient summary 2026-09-24; United States; partial summary Fish, Koi; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Saki-Hikari Color Enhancing Saki-Hikari Color Enhancing, editorial ingredient summary 2026-09-24; United States; partial summary Fish, Koi; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Saki-Hikari Fancy Goldfish Color Enhancing Saki-Hikari Fancy Goldfish Color Enhancing, editorial ingredient summary 2026-09-24; United States; partial summary Fish, Goldfish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Saki-Hikari Growth Saki-Hikari Growth, editorial ingredient summary 2026-09-24; United States; partial summary Fish, Koi; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Saki-Hikari Multi-Season Saki-Hikari Multi-Season, editorial ingredient summary 2026-09-24; United States; partial summary Fish, Koi; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Sera Betta Granules Sera Betta Granules, editorial ingredient summary 2026-09-24; ; partial summary Bettas, Fish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Sera Immune Probiotic Granules Sera Immune Probiotic Granules, editorial ingredient summary 2026-09-24; ; partial summary Fish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Sera San Color Granules Sera San Color Granules, editorial ingredient summary 2026-09-24; ; partial summary Fish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Sera Vipachips Wafers Sera Vipachips Wafers, editorial ingredient summary 2026-09-24; ; partial summary Fish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
  • Sera Vipagran Granules Sera Vipagran Granules, editorial ingredient summary 2026-09-24; ; partial summary Fish; Source data captured; Label verification pending; Evidence applicability requires the stated ingredient and study review scope
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