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Fish Oil for Dogs and Cats: Dosage, Safety, and Health Benefits

dog and cat next to food bowl

Pets are the best, aren’t they? They provide joy and companionship, reduce stress, and can even support heart health.1,2 (Off the record—they also provide many of the same joys and photo opportunities as children, without all the “talking back” and extra laundry). However, being a pet owner does come with some important responsibilities—like ensuring they get the nutrients they need to thrive.

Well, what if we told you that your pets are likely deficient in nutrients affecting the health of virtually every cell in their bodies, as well as their behavior and trainability? (Because if they eat commercial pet foods, they probably are). Most pet foods—whether dry, canned, or raw—typically contain higher amounts of omega-6 fatty acids from vegetable oils and lower amounts of omega-3 fatty acids from fish oil.3 This is far from optimal, considering that an unhealthy ratio of omega-6 to omega-3 fatty acids has been shown to negatively affect everything from animals’ skin, hearts, brains, and kidneys to their inflammatory response.4 Woof.

But don’t worry, we can help. In this article, we’ll talk about why cats and dogs need omega-3 fatty acids, and how to ensure they receive their fair share of these all-important fats. 

Essential Fatty Acids 

Despite fat’s reputation for being “unhealthy,” it is actually quite important for cellular health. For example, fats provide energy, support the absorption of fat-soluble vitamins, and help modulate inflammation.4 What’s more, because fat makes up most of the membranes of cells and organelles, our bodies actually require a certain amount of it to function properly. 

A particularly important family of fats are polyunsaturated fatty acids (PUFAs). Often referred to as “healthy fats,” PUFAs are distinguished at the molecular level from saturated and monounsaturated fatty acids by the presence of at least 2 double bonds between carbons within the fatty acid chain. Depending on the location of a fat’s first double bond from the methyl (omega) end of the molecule, PUFAs can be categorized as omega-3 or omega-6.

Omega-3 and omega-6 fatty acids are necessary for the normal structure and function of cell membranes; however, mammals lack the fatty acid desaturase enzymes (i.e., delta-15 and delta-12 desaturase) needed to make omega-3 and omega-6 fatty acids in the body. Thus, these essential PUFAs must be consumed through dietary sources.5

Omega-3 PUFAs 

Sources and Metabolism

The three types of omega-3 fatty acids involved in human and animal physiology are alpha-linolenic acid (ALA; containing 18 carbons with 3 double bonds [18:3]), eicosapentaenoic acid (EPA; 20:5), and docosahexaenoic acid (DHA; 22:6). ALA is the parent fatty acid of the omega-3 family and gives rise to EPA and DHA through a complex series of metabolic reactions involving desaturation (the addition of a double bond) and elongation (lengthening of the fatty acid’s carbon chain). ALA can be found in plant-based dietary sources including flaxseed, chia seeds, walnuts, and vegetable oils. 

EPA and DHA are found primarily in marine sources, such as fatty fish, fish oil, and phytoplankton. Although cats and dogs can theoretically use ALA to form EPA and DHA, their conversion rates are so low, that it is generally recommended that cats and dogs obtain EPA and DHA directly from marine sources rather than sources rich in their ALA precursor.5,8 For reasons we’ll explain in the coming section, it should also be noted that large doses of omega-3 ALA can actually lead to an essential fatty acid deficiency in cats, whereas supplementing with EPA and DHA does not pose the same concern.7

Omega-6 PUFAs 

Sources and Metabolism 

Omega-6 PUFAs, including linoleic acid (LA; 18:2) and arachidonic acid (AA; 20:4), are fatty acids found in vegetable oils, nuts, seeds, and animal meats.  Similar to ALA, LA must be consumed through the diet in order to give rise to AA and its other long-chain PUFA derivatives via desaturation and elongation processes. However, because cats show markedly little delta-6 desaturase activity (an enzyme needed to convert LA to AA), it is generally recommended that they obtain direct sources of AA.7

Differential Effects on Cellular Heath

Despite their shared essentiality for overall health, omega-3 and omega-6 fatty acids can have very different effects when consumed in large amounts.4,9 Upon ingestion, both omega-3s and omega-6s are incorporated into membrane phospholipids where they play fundamental roles in regulating membrane properties and cellular signaling.9 However, whereas omega-3s help initiate cellular processes and signaling molecules that reduce cell stress and support a healthy inflammatory response, omega-6s can give rise to signaling molecules that promote an inflammatory response.9

What’s more, because omega-3s and omega-6s compete for the same enzymes needed to synthesize their PUFA derivatives, an increase in the omega-6 contents of a cell typically occurs at the expense of its omega-3s and vice versa.7,9 For this reason, feeding cats a diet high in ALA and low in LA can lead to an essential fat deficiency because ALA and LA will compete for the enzymes needed to synthesize AA. (In other words, either ALA will get the enzymes needed to synthesize EPA, or LA will get the enzymes needed to synthesize LA). 

To help minimize the pro-inflammatory effects of omega-6s and maximize the health-promoting effects of omega-3s, it is generally advised that mammals consume a balanced ratio (around 6:1 or less) of omega-6s to omega-3s from EPA+DHA.7,9

Evidence-Based Benefits for Cats and Dogs 

Still not convinced that omega-3s are vital for your pet’s health? A growing literature finds that supplementation with EPA and DHA can provide a wide range of beneficial effects for cats and dogs.4 Although these fatty acids naturally occur and function together, they each have their own distinct, yet mutually supportive role in promoting pet health. (Note: the references with a * denote studies with cats, and references without * are studies with dogs). 

EPA plays a significant role in cats’ and dogs’: 

DHA plays a foundational role in cats’ and dogs’:                                               

  • Cellular and Immune Health10,26*,27
  • Brain Development28*29*,3031
  • Eye Development28*,30
  • Trainability and Behavioral Health3234

Although comparatively fewer studies have looked at the effects of omega-3 supplementation in cats relative to dogs and humans, the evidence to date suggests EPA and DHA offer cats many of the same benefits as other mammals.3,4

Is My Pet Getting Enough Omega-3s?                   

If your cat or dog eats commercial pet food, check the nutrition label to see if fish oil is listed as an ingredient, or whether it has been enriched with EPA and DHA.  However, keep in mind that even if the ingredients do list omega-3 sources (e.g., salmon, salmon meal, trout, etc.), many pet foods are manufactured at very high temperatures, which are detrimental to temperature-sensitive omega-3 fatty acids. This means that, even if their food does contain omega-3 sources, it will be difficult to know whether the amounts they are actually receiving are sufficient for foundational health.3,4

Compounding this issue further, because many commercial pet foods contain high amounts of omega-6s from vegetable oils, this will also affect the amount of omega-3 fatty acids that are ultimately available to your pet’s cells.7

How Much Supplemental Omega-3 Does My Pet Need?

There isn’t a consensus on omega-3 dosing guidelines for animals; however, veterinarians and the National Research Council (a highly credible organization dedicated to the application of scientific research) generally adhere to the following weight-based recommendations for dogs and cats:5

Dogs: 50-75 mg of EPA+DHA (combined) per kg of body weight 

Cats: 30-50 mg of EPA+DHA (combined) per kg of body weight 

For reference, this would amount to 500-750 mg of EPA+DHA per day for a dog weighing 10 kg (~22 lbs.) and 150-250 mg of EPA+DHA per day for a cat weighing 5 kg (~11 lbs.). However, a number of variables factor into the amount of EPA and DHA your pet will need to meet its cellular health needs. These variables include: 

1. Size and Breed of Pet

  • Different animal breeds and sizes will require different amounts of PUFAs to maintain optimal cellular health.4

2. Stage of Life

  • Growing puppies and kittens often require greater amounts of omega-3s (particularly DHA) for proper retinal and brain development.5

3. Health Status 

  • Conditions affecting the health of the heart, kidneys, joints, and inflammatory response often require greater amounts of EPA+DHA.4,6

4. Amount of PUFAs Consumed in Diet 

  • Different pet foods provide different amounts of PUFAs and will require different amounts of additional omega-3 supplementation.3

In light of all of these variables, we recommend talking to your pet’s veterinarian about their specific cellular health needs and integrating EPA and DHA into their diets accordingly. This can be done most efficiently by providing these fatty acids in a supplemental form, such as fish oil.

Selecting a Quality Fish Oil Supplement

When selecting a fish oil supplement for your pet, it is important to adhere to a few guidelines. More specifically, you should look for a high-quality product that is: 

  1. High in EPA and DHA—as opposed to ALA, which animals cannot convert into EPA and DHA efficiently.6,8
  2. Triglyceride form—as opposed to ethyl-ester or synthetic forms, which are less easily absorbed and utilized by the body than omega-3s in the natural triglyceride form.3,5
  3. Free of toxins and pollutants—pay special attention to whether the manufacturer takes measures to avoid common contaminants like mercury.4
  4. Manufactured and stored using methods that limit oxidation—the highly unsaturated nature of omega-3 fats makes them susceptible to rancidity, and special measures should be taken to reduce their exposure to heat, light, and other sources of oxidation.4
  5. Third-party tested for quality control—nutritional supplements are not tested by the FDA, so choose a manufacturer that voluntarily undergoes third-party testing to verify their ingredients, purity, and safety.

Potential Side Effects 

Another important reason to talk to your pet’s veterinarian before starting with omega-3s (or any dietary supplement) is the potential for side effects. Although uncommon, instances of altered blood-clotting, gastrointestinal upset, increased oxidative stress, and altered wound-healing have been reported in cats and dogs.36 In order to better evaluate how your pet might handle starting a supplemental fish oil regimen, talk to their veterinarian.

 In Closing

Pets are the best, and as their owner, you only want what’s best for them. According to a growing body of research, what’s “best” includes a more balanced ratio of omega-6 to omega-3 fats. If your pet’s food is lacking in important omega-3 fats, consult your veterinarian about whether and how much EPA and DHA your pet needs for optimal health across life stages.

Gina Jaeger, PhD is a Developmental Specialist and Lead Research Writer for Nordic Naturals. She holds a doctorate in Human Development, and has published several research articles on children's cognitive development. Gina enjoys studying and educating others on strategies for optimizing health and wellness throughout the lifespan.

Desaturation: When a saturated compound gets converted into an unsaturated compound by the removal of two hydrogen molecules and the addition of a double bond.

Elongation: A metabolic process wherein a fatty acid’s carbon chain gets lengthened by an enzyme complex called elongase.

Fatty acid desaturase: Enzymes that introduce double bonds into fatty acid chains and help maintain the structure and function of cell membranes.

Phospholipids: A major component of all cell membranes; a type of lipid molecule made up of two fatty acids, a phosphate, and a glycerol molecule.

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