Is Fish Oil Healthy for My Dog or Cat?

Fish oil is often recommended for dogs and cats for the omega 3 fatty acids it contains. Omega 3 fatty acids possess anti-inflammatory properties that can be useful for inflammatory conditions like allergies, arthritis and heart disease. However, there is more to this story than just ‘fish oil = healthy, anti-inflammatory qualities’, and our discussion on this topic will help to educate you and support our evolving, less than enthusiastic position on fish oil for general use as a supplement.

The Health Benefits of Fish Oil

The health benefits of fish oil that receive the most attention include its ability to aid in the treatment of various heart diseases, lower high cholesterol, reduce inflammation associated with arthritis, allergies, skin issues and inflammatory intestinal conditions, treat depression, help remedy eye disorders and help to prevent neurodegenerative diseases such as MS, Parkinson’s Alzheimer’s disease.

Most of the health benefits of fish oil can be attributed to the presence of the omega 3 fatty acids Docosahexaenoic acid (DHA) that provides nutrients important for proper fetal development including the eyes, brain and nervous system and Eicosapentaenoic acid (EPA) that provides the primary anti-inflammatory, immune system boosting and platelet aggregation inhibiting properties.

Contaminants in Fish Oil

Fish oils can contain numerous different contaminants, however the ones most focused on include PCB’s, mercury and dioxin. These are generally the result of industrial pollutants that are directly discharged into waterways or washed into our oceans due to rainfall via runoff or by cleaning the air from this particulate pollution as it rains.

A recent study provided some good news when it found that the majority of fish oil products tested contained only very low levels of mercury, ranging from one to six parts per billion per serving. That range is far below the upper safety limit of 100 parts per billion set by the Global Organization for EPA and DHA Omega-3s, or GOED, an industry trade group.

What this means is that taking a fish oil supplement can be safer than eating the fish itself as companies use techniques such as molecular distillation to cleanse fish oil of impurities. However, this “cleansing” of fish oil can have its own drawbacks. That is because the EPA and DHA in fish oil are delicate, polyunsaturated oils that go rancid very quickly creating potentially harmful free-radicals when exposed to heat, light or oxygen. This is why it is so important that fish oil contains antioxidants like vitamin E or rosemary extract. Because of this potential for rancidity you should check something called the “peroxide value” on the fish oil’s Certificate of Analysis. This is a measure of rancidity reactions in the oil that have occurred during processing and/or storage and should be less than 5 meq/kg.

Due to distillation you should also make sure that the fish oil you purchase is in its natural triglyceride form because that is how it is found in nature. This issue occurs because during the distillation process, in order to to purify the oil, it is necessary to add ethanol (an industrial alcohol) to form a synthetic substrate. In a vacuum, the mix is then distilled and the result is a concentrated omega-3 ethyl ester solution. The benefit is a pure fish oil, and the ability to concentrate the healthy omega-3’s like DHA and EPA. This is why almost all of the “highly concentrated” fish oils are in the ester form. Unfortunately, research is now showing that although this form of fish oil can yield higher concentrations of omega-3s, it is not absorbed nearly as well as natural fish oil. Manufacturers can in fact convert the omega-3 concentrated ester form back into the healthy triglyceride form, but most manufacturers do NOT do this because the costs are significantly higher.<

Why Do Contaminants Accumulate in Fish?

The consumption of fish is by far the most significant source of ingestion-related mercury exposure in humans and animals. Mercury is present in only very small concentrations in seawater. However, it is absorbed, usually as methyl mercury, by algae at the start of the food chain. This algae is then eaten by fish and other organisms higher in the food chain. Fish efficiently absorb methyl mercury, but only very slowly excrete it so mercury will accumulate in tissue, which is called bioaccumulation.

The older that such fish become, the more mercury they may have absorbed. Anything that eats these fish also consumes the higher level of mercury that the fish have accumulated. This process explains why predatory fish such as swordfish and birds like ospreys and eagles have higher concentrations of mercury in their tissue than could be accounted for by direct exposure alone.

Species on the food chain can amass body concentrations of mercury up to ten times higher than the species they consume. This process is called biomagnification. For example, herring contains mercury levels at about 0.1 parts per million, while shark contains mercury levels greater than 1 part per million. That is why in the past we have always recommended fish oils from smaller fish like sardine and anchovies that are closer to the beginning of the food chain.

Is Fish Oil Necessary for my Dog or Cat’s Diet?

When people typically talk about fish oil they are referring to the content of the omega 3 fatty acids EPA and DHA. So the answer to the above question would be no, a healthy dog or cat does not require supplementation with fish oil.

DHA is important for proper brain, nervous system and eye development. Fortunately, nature take cares are of this by increasing DHA production in the mother that is transferred to puppies and kittens during pregnancy and lactation. As I mentioned previously DHA supplementation is not necessary, however it can be beneficial for pregnant females and also to help maintain the health of the eyes, brain and nervous system to treat various imbalances or weaknesses in this tissue.

As far as EPA goes, this fatty acid has anti-inflammatory benefits that will be helpful for issues like arthritis, autoimmune conditions, allergies and so on. This does not need to be supplemented in healthy animals because they can derive what they need from a healthy diet that includes grass fed meats, free-range eggs, organ meats, organic greens and some fish. You may notice that I specifically said a “healthy” diet. That is because if you feed a typical pet food that uses factory farmed meat that is finished on feed lots, low-quality farm-raised fish, flours and grains, factory farmed eggs (well you get the picture), you will be feeding your canine or feline a diet that has an unhealthy, or pro-inflammatory, ratio of omega 6 to omega 3. In this case you can change the diet over to healthier foods or include fish oil supplementation in your pet’s diet.

Are There Alternatives to Fish Oil?

Since dogs and cats do not convert the essential omega 3 fatty acid alpha linolenic acid to EPA and DHA efficiently, supplementing your dog with oils like flax seed, hemp seed, chia seed and other similar oils will not do the trick. Even though those other oils do have various health benefits, fish oil has been the primary provider of the beneficial omega 3 fatty acids EPA and DHA up until recently.

We have always been a proponent of algae for all their important nutrients, but they have suffered from the same problems as fish oil and that is pollutants. That was until we found BioPreparation, which is a balanced blend of four algae that is grown in indoor bioreactors where the environment can be isolated from outdoor pollutants. While these algae are a great source of fatty acids they are not a concentrated source. Fortunately, with all the issues related to sustainability and pollution, algae has started to be grown indoors for the purpose of providing a cleaner, more sustainable source of the omega 3 fatty acids EPA and DHA. This is wonderful news and makes algae oil the only real alternative to fish oil that is both less polluted and highly sustainable.

In Conclusion

Well, is fish oil good for your dog or cat? From what we discussed above, it really depends. It can be in the case of various disorders that can benefit from the addition of EPA and DHA, the omega 3 fatty acids found in fish oil. However, it depends strongly on the quality of the fish oil you decide to use in your supplement regimen. If you choose the cheapest fish oil, without doing further research on that brand, you may be doing more harm than good.

For healthy dogs and cats fish oil is really not necessary, especially when you are feeding healthier grass fed foods naturally higher in omega 3 fatty acids. Though, as mentioned previously, if you feed a typical store bought brand of kibble pet food, your canine or feline could benefit from the increase in omega 3 fatty acids from fish oil. However, the issues of quality and sustainability will be spurring us to make the transition to obtaining our EPA and DHA from algae oil for ourselves and our customers in the future.


Health benefits of fish oil. Retrieved from

Mercury in fish. Retrieved from<

Kresser, C. The definitive fish oil buyers guide. Retrieved from

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