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The Effects of Omega-3 Supplementation on the Omega-3 Index and Quality of Life and Pain Scores in Dogs

A 16-week clinical study in 29 pet dogs found that daily omega-3 supplementation from anchovy and sardine oils significantly increased the Omega-3 Index in all size groups and reduced owner-reported pain in small and medium dogs. Large dogs did not show the same pain improvement, likely because fixed-size capsules delivered a lower mg/kg dose. No adverse effects were reported.

Last Reviewed Date: 01/14/2026

Overview

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Carlisle, C., Metzger, B.T., Tintle, N.L., Polley, K., Jackson, K.H., Le Brun-Blashka, S., Griffiths, J., & Harris, W.S. (2024). Animals, 14(21), 3108. https://doi.org/10.3390/ani14213108

Purpose of the Study

The researchers aimed to determine whether daily supplementation with marine omega-3 fatty acids, EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), could:

Increase the Omega-3 Index (O3I), a blood measure of EPA + DHA levels.
Improve owner-reported pain and quality of life (QOL) scores.

They note their findings support the hypothesis that increased EPA + DHA intake in dogs may provide health benefits, while recognizing that further research is needed to define target O3I levels and optimal doses for specific health conditions.

Study Type

Open-label clinical study in client-owned dogs, conducted at five U.S. veterinary clinics.

Species Studied

Dogs (various breeds, ages 3+, healthy at enrollment other than some pain).

Dosage Context in the Study

The researchers compared their chosen dose to guidance from the National Research Council (NRC), a U.S. science body that sets nutrient requirements for animals.

For omega-3s in dogs, the NRC guidance is:

Purpose	mg/kg/day	mg/lb/day	Meaning
NRC minimum	30	~13.6	Minimum to maintain basic metabolic functions in a healthy adult dog.
NRC upper end for health outcomes	370	~168	Higher intake that may be needed to help manage certain health problems.
Dose used in this study	~68–70	~31	More than double the NRC minimum but far below the NRC’s high-end range; selected to see if a moderate, practical dose could raise O3I and improve comfort in healthy dogs.

Conversion note: To go from mg/kg to mg/lb, divide by 2.2.

Study Methods

Researchers conducted a 16-week clinical study with 29 adult pet dogs of various breeds and sizes. All dogs were generally healthy but had owner-reported signs of pain at the start. The team grouped dogs by size as small (≤11 kg), medium (12–27 kg), or large (≥28 kg).

Each dog received soft gel capsules made from anchovy and sardine oils, aiming for about 70 mg of combined EPA and DHA per kilogram of body weight per day. Because the capsules came in a fixed size, researchers could more precisely meet the target dose in smaller dogs. Large dogs often received a lower effective mg/kg dose, which became important when interpreting results.

The team measured:

Omega-3 Index using dried blood spot testing.
Pain with the Helsinki Chronic Pain Index (HCPI).
Quality of Life using the Canine Health-related Quality of Life Survey (QLS).

Key Findings

Omega-3 Index (O3I)

Increased from 1.4% → 3.3% on average (+136%).
All size groups saw significant improvement.

Pain Scores

Overall reduction of ~16–19%, driven by:
- Small dogs: −38%
- Medium dogs: −30%
- Large dogs: No significant change (likely due to lower mg/kg dosing from capsule size constraints).

Quality of Life (QOL)

No significant overall change (baseline scores were already high at 8.9/10).
Small dogs showed a modest but statistically significant improvement.

Safety

No adverse events reported.

Researchers’ Context on Pain Mechanism

The authors explain that although inflammation was not directly measured, pain and inflammation are closely related in dogs. They provide context that EPA and DHA produce metabolites that tend to be anti-inflammatory compared to those derived from arachidonic acid. These fatty acids can compete with arachidonic acid for enzymes, reducing the production of pro-inflammatory compounds. In dogs, this may help alleviate pain from inflammatory conditions such as osteoarthritis.

Limitations Noted by the Authors

No placebo group.
Relatively small sample size.
Home diets were not standardized.
Large dogs received a lower mg/kg dose in practice.

Authors’ Conclusion

Supplementation at ~70 mg/kg/day (~31 mg/lb/day) improved omega-3 status and reduced pain scores in small and medium dogs. The authors suggest future studies might target an O3I of >3% as a tentative threshold for improved health metrics, and that higher dosages could be explored.

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General Health Topics

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Cardiovascular & Blood	At a Glance The cardiovascular system includes the heart and blood vessels, which transport oxygen and nutrients throughout the body. Blood health is equally important, as it carries immune cells, regulates clotting, and removes waste. Conditions like heart disease, anemia, or blood clotting disorders can severely impact a dog’s energy, endurance, and longevity. Connecting the Dots The Omega-3 Index measured in the study reflects the EPA and DHA content of red blood cells, a biomarker for cardiovascular health. Increasing omega-3 levels improves blood fluidity and endothelial function in both humans and dogs. The study confirmed that EPA + DHA supplementation effectively elevates Omega-3 Index levels in all dogs tested. Higher Omega-3 Index values are associated with better heart health and reduced systemic inflammation.
Endocrine & Metabolic	At a Glance The endocrine system is a network of glands that produce hormones, which regulate essential body functions like metabolism, growth, stress response, and organ function. The metabolic system controls how the body converts food into energy and maintains balance in key nutrients. Disorders like diabetes, hypothyroidism, and Cushing’s disease occur when hormone production is too high or too low, leading to widespread effects on weight, energy, digestion, and immune health. Maintaining endocrine balance is crucial for overall well-being and longevity. Connecting the Dots The study referenced National Research Council (NRC) guidance that at least 30 mg of EPA + DHA per kg body weight is required to maintain normal metabolic functions in adult dogs. Although metabolic markers were not directly measured, this reference establishes omega-3s as nutritionally essential for metabolic maintenance. The observed rise in the Omega-3 Index reflects the systemic incorporation of long-chain fatty acids that contribute to overall metabolic efficiency.
Immune System	At a Glance The immune system is a complex, body-wide network that protects dogs from infections, helps resolve injury, and monitors for internal abnormalities. It also plays a role in regulating inflammation and maintaining tolerance to non-harmful exposures such as food proteins or pollen. A well-regulated immune system allows dogs to recover from illness efficiently and respond appropriately to everyday challenges without damaging healthy tissue. Connecting the Dots Omega-3 fatty acids (EPA and DHA) influence immune regulation by reducing pro-inflammatory cytokines and promoting anti-inflammatory mediators. The study’s pain improvement findings are linked to decreased immune-driven inflammation in tissues and joints. EPA and DHA compete with arachidonic acid in immune cell membranes, lowering production of inflammatory eicosanoids. These effects support an overall balanced immune response and improved well-being in dogs.
Inflammation	At a Glance Inflammation is the body's biological response to harmful stimuli such as injury, infection, or toxins. It involves immune cells, blood vessels, and molecular signals working to repair tissue and defend against threats. In dogs, while acute inflammation is beneficial for healing, chronic inflammation can contribute to diseases like osteoarthritis, allergies, and cardiovascular issues, causing ongoing damage to tissues and organs. Connecting the Dots Inflammation reduction was a key mechanism behind the decreased pain scores seen in the study. EPA and DHA replace arachidonic acid as precursors to signaling molecules, reducing COX-2–mediated inflammatory pathways. Anti-inflammatory effects of omega-3s help manage chronic pain conditions in dogs, especially musculoskeletal disorders. The study supports using omega-3s as a natural tool to regulate inflammation and improve quality of life.
Joint & Musculoskeletal	At a Glance The joint and musculoskeletal system provides the strength, stability, and mobility that dogs rely on for everything from running and jumping to maintaining posture and balance. This system includes bones, joints, muscles, tendons, and ligaments, all working together to support movement. Over time, wear, injuries, or genetic conditions can lead to pain, stiffness, or reduced mobility, impacting a dog’s quality of life. Proactive care, therapeutic interventions, and lifestyle strategies can help support musculoskeletal health and keep dogs moving comfortably as they age. Connecting the Dots Dogs receiving omega-3 supplementation showed reduced pain, reflecting improved joint comfort and mobility. EPA and DHA’s anti-inflammatory properties lessen stiffness and inflammation associated with osteoarthritis and aging joints. The findings align with prior research showing omega-3s help manage chronic musculoskeletal pain in dogs. Improved movement and reduced discomfort contribute directly to enhanced quality of life scores.

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Health Conditions

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Therapeutic Interventions

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Lifestyle Strategies

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Foods

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Anchovies	At a Glance Anchovies are small, oily saltwater fish that are highly bioavailable and naturally low in contaminants due to their short lifespan and plankton-based diet. For dogs, they offer a clean, sustainable source of protein and omega-3 fatty acids. Connecting the Dots The marine oil used in the study was sourced in part from anchovy, a small fish rich in EPA and DHA. Anchovy contributed to the improved Omega-3 Index and pain-reducing benefits observed during the 16-week supplementation period. The findings highlight anchovy as a bioavailable and sustainable source of long-chain omega-3 fatty acids for dogs.

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Food Components

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Nutrients

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DHA (Docosahexaenoic Acid)	At a Glance DHA (Docosahexaenoic Acid) is a long-chain omega-3 fatty acid essential for maintaining cell membrane structure, particularly in the brain and eyes. It also plays a key role in supporting cognitive function and reducing inflammation at the cellular level. Connecting the Dots DHA, supplied at 200 mg per capsule, was co-administered with EPA to deliver a total daily intake averaging 68 mg EPA + DHA per kg of body weight over 16 weeks. Small and medium dogs received the higher relative doses (about 75 mg/kg/day) and experienced the greatest reductions in pain scores. DHA contributed to anti-inflammatory effects through the generation of less inflammatory lipid mediators compared with arachidonic-acid derivatives. The study’s findings confirmed that DHA, together with EPA, was effectively incorporated into red-blood-cell membranes, supporting measurable improvements in comfort and mobility.
EPA (Eicosapentaenoic Acid)	At a Glance Eicosapentaenoic acid (EPA) is a long-chain omega-3 fatty acid most commonly found in marine sources like fish and algae. In dogs, it supports a balanced inflammatory response and is often used to promote joint, skin, and overall health, particularly in aging dogs or those with chronic conditions. Connecting the Dots EPA was one of the two long-chain omega-3 fatty acids supplemented in the study, provided at 250 mg per capsule within a daily dosage averaging 68 mg EPA + DHA per kg of body weight. Dogs received between approximately 53 and 76 mg of total omega-3s per kg depending on size, administered for 16 weeks. EPA helped reduce inflammation by competing with arachidonic acid, producing fewer pro-inflammatory mediators and contributing to lower pain scores. The increase in red-blood-cell EPA reflected a 136% rise in the Omega-3 Index, demonstrating effective tissue incorporation and metabolic uptake.

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Food Metas

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Food Types

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Fish	At a Glance Fish are aquatic, gill-bearing animals that live in fresh or salt water and serve as a rich natural source of protein, omega-3 fatty acids, and essential minerals for dogs. In canine nutrition, fish typically refers to edible marine or freshwater species used whole, as fillets, or as processed meals and oils. The type of fish, its size, and its place in the ocean food chain influence its nutritional value, safety, and sustainability. When responsibly sourced, fish offers dogs a highly digestible protein and a sustainable way to support skin, joint, brain, and heart health. Connecting the Dots The omega-3 supplement studied was derived from marine fish, confirming fish as the natural dietary source of EPA and DHA for dogs. Marine fish oils supplied the long-chain omega-3 fatty acids that significantly raised dogs’ Omega-3 Index after 16 weeks of supplementation. The study supports fish-derived nutrients as effective components for improving blood fatty-acid status and reducing inflammation-related pain in dogs.

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Food Component Groups

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Fish Oil	At a Glance Fish oil is derived from the tissues of a variety of fish species, including both small oily fish like anchovies and sardines, as well as larger species such as salmon and mackerel. It is a rich source of omega-3 fatty acids, particularly EPA and DHA. Connecting the Dots Fish oil was the delivery form for the omega-3 fatty acids tested in this study. Daily supplementation with fish oil rich in EPA and DHA doubled the Omega-3 Index and reduced pain scores in dogs. The discussion cites fish oil’s anti-inflammatory activity and previous evidence of its benefits for canine joint health.

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Nutrient Classes

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Nutrient Types

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Nutrient Sub-Types

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Omega-3 Fats	At a Glance Omega-3 fatty acids are healthy fats that dogs can’t make on their own and must get through food or supplements. They keep cells flexible and functioning properly, which supports healthy skin, a shiny coat, and strong heart, joint, and brain health. Omega-3s also help control inflammation, allowing the body to recover efficiently and maintain overall comfort and resilience. Connecting the Dots The study evaluated marine omega-3 fatty acids for their effects on dogs’ blood profiles and pain levels. Sixteen weeks of supplementation led to a 136% increase in the Omega-3 Index and lower pain scores in small and medium dogs. The discussion attributes these improvements to omega-3s’ ability to regulate inflammatory signaling and support systemic health.

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Dig Deeper

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Title	URL	At a Glance

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The Effects of Omega-3 Supplementation on the Omega-3 Index and Quality of Life and Pain Scores in Dogs

Contents

Overview

Purpose of the Study

Study Type

Species Studied

Dosage Context in the Study

Study Methods

Key Findings

Researchers’ Context on Pain Mechanism

Limitations Noted by the Authors

Authors’ Conclusion

General Health Topics

Health Conditions

Therapeutic Interventions

Lifestyle Strategies

Foods

Food Components

Nutrients

Food Metas

Food Types

Food Component Groups

Nutrient Classes

Nutrient Types

Nutrient Sub-Types

Dig Deeper