Getting the Fat on Fatty Acids

By Shawn Messonnier DVM
A resource from Pet-Togethers

Fatty acids are among the most commonly used nutritional supplements used in treating dogs and cats. Fortunately, they have been used successfully long enough that most conventional veterinarians include their usage in the treatment of at least some diseases. This article will discuss our current knowledge of fatty acids and present some new ideas for their usage in treating our pets.

Medicinal fatty acids are divided into omega-3 and omega-6 fatty acids. In general, omega-6 fatty acids tend to promote inflammation, whereas omega-3 fatty acids act to reduce inflammation. As such, omega-3 fatty acids are used in diseases in which anti-inflammatory activity is needed. The fatty acids can substitute for medications such as corticosteroids in the treatment of inflammation.

The most commonly used supplements that provide fatty acids are fish oil and flax seed oil. While flax seed oil containsmore omega-3’s than fish oil, the omega-3’s found in flax seed oil are in an inactive form. The omega-3’s found in fish oil are in an active form. In research studies, fish oil has shown positive benefits in helping people and pets with disease, whereas flax seed oil has not been as beneficial. For this reason, fish oil is generally recommended as the omega-3 fatty acid supplement of choice.

The active omega-3’s, (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) are derived from fish oils of coldwater fish (salmon, trout, or most commonly menhaden fish.) Also called linseed oil, flaxseed oil is derived from the seeds of the flax plant and has been proposed as a less smelly alternative to fish oil. Flaxseed oil contains alpha-linolenic acid (ALA,) an omega-3 fatty acid that is ultimately converted to EPA and DHA. In fact, flax seed oil contains higher levels of omega-3 fatty acids (ALA) than fish oil. It also contains omega-6 fatty acids.

Similar to the situation with fish oil, pets with inflammatory diseases may respond to supplementation with flax seed oil. However, many species of pets (probably including dogs and cats) and some people cannot efficiently convert ALA to the more active non-inflammatory omega-3 fatty acids (EPA and DHA.) In one study in people, flax seed oil was ineffective in reducing symptoms or raising levels of EPA and DHA. In pets with kidney disease, flax seed oil was not as effective as fish oil. While flaxseed oil has been suggested as a substitute for fish oil, there is no evidence that it is effective when used for the same therapeutic purposes as fish oil. Unlike the case for fish oil, there is little evidence that flax seed oil is effective for any specific therapeutic purpose with the following exceptions. Flax seed oil can improve the coat and skin of pets. Also, the lignans contained in flax seed oil may have anti-cancer benefits.

Fish oil supplementation may be helpful for pets with inflammatory diseases including allergies, arthritis, kidney disease,heart disease, and cancers. People with diabetes may have fatty acid derangement and require supplementation; this may also be true in pets. Fish oil has demonstrated benefits in people and pets with allergies, kidney disease, and heart disease. It has also shown benefits as an anti-depressant in people with mild depression. Fish oil appears to have benefits in pets with arthritis as well. Pets with any type of inflammatory disease may benefit from fish oil supplementation. In general, more severe disease requires doses higher than those commonly recommended and often additional supplements are necessary as fish oil is not often useful as the only supplement.

Fish oil is very effective in some pets with allergic skin disease. It is easy to administer (via gel caps or liquid) and can reduce the amount of corticosteroid or antihistamine needed to control itching. The response is variable in other diseases (such as kidney disease) but fish oil appears effective in research studies. In pets with some types of cancer, fish oil has slowed down the growth and spread of the cancer. While more studies are needed on other types of cancer, the general recommendation is to add fish oil to the diets of all pets with cancer.

In my opinion, any pet may benefit from fatty acid supplementation. While we don’t always have hard “proof” that they work in every case, the science is there to show how they work and suggest their usage any time inflammation may be a problem. In most pets in my practice, fatty acid supplementation forms the “baseline” of supplements that I use, adding other supplements as dictated by clinical response or the nature of the disease.

While there is concern about the contamination of fish meat with environmental contaminants such as mercury, this concern does not apply to fish oil. Supplementation with fish oil can result in decreased levels of vitamin E; therefore, fish oil supplements have extra vitamin E added to them.

As is true with many supplements, your veterinarian may have favorite supplements that he will sell you or recommend to you. Pet owners are cautioned against buying supplements without knowledge of the manufacturer, as supplements are not highly regulated and some supplements may not contain the labeled amount of fish oil.


Fish oil supplementation is very safe. The most common side effect seen in people and pets is a fish odor to the breath or the skin. Because fish oil has a mild “blood-thinning” effect, it should not be combined with powerful blood-thinning medications, such as Coumadin (warfarin) or heparin, except on a veterinarian's advice. Fish oil does not seem to cause bleeding problems when it is taken by itself at commonly recommended dosages. In people, a high dose of fish oil (4 grams or more each day) when combined with ginkgo biloba has caused serious bleeding problems. Fish oil does not appear to raise blood sugar levels in people or pets with diabetes despite earlier concerns about this. Flax oil does not appear to cause “blood thinning.” In my practice, I’ve never seen any side effects and I use a lot of fatty acids. Very rarely, I have had a few of my canine patients smell fishy. This side effect goes away as the dosage is lowered. While many owners worry about giving extra “fat” to their pets, especially in cases where the pet is overweight, take comfort. Fatty acid supplements contain only a handful of calories and supplementation is unlikely to hurt any pet on a diet.

In studies done in people and pets, dosages much higher than label doses are needed to achieve results. As a rule, I try to start with 2-4 times the label dose when treating diseases and adjust the dose depending upon the pet’s response. I use the label dose when recommending fatty acids as a coat or skin supplement.

Fatty acid therapy is becoming a part of our mainstream therapy for many pet disorders. In general, fish oil is preferred to flax oil as it contains the more active omega-3’s. To get the best results, dosages higher than those on the label are needed and in most cases, fish oil should be combined with other supplements for maximum effectiveness.


About Pet-Togethers
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