Does this Seem (not…) Fishy to You?

Today, let’s talk about fish and fish oil, and the types of fat that these pet food ingredients can contribute to your dog’s food.

Some Background: Dietary fat, more specifically, fatty acids, are classified into families. Two of the most important are the omega-6 fatty acids and the omega-3 fatty acids. Both types are important in a dog’s diet, but dog foods (like human foods) tend to contain an over-abundance of omega-6 fatty acids. This occurs because of the types of ingredients that are produced by modern-day agricultural systems. A well-balanced diet contains optimal amounts of both omega-6 and omega-3 fatty acids.

Three fatty acids in the omega-3 family are of interest, nutritionally. These are the parent omega-3 fatty acid called alpha-linolenic acid (ALA), which is found in flax seed, borage oil, other vegetable oils and some nut oils. Alpha-linolenic acid can be converted to two larger omega-3 fatty acids; these are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Although most mammals can convert some ALA to EPA and DHA, this conversion is not highly efficient. Rather, the best converters of ALA to long-chain omega-3 fatty acids are algae. As a result, fish species that consume algae (and other fish that consume those fish) are the best concentrated sources of EPA and DHA in the diets of both humans and dogs. Most nutritionists agree that the best way to increase these beneficial fatty acids in dogs’ diets is by enriching a dog’s food with the oils of salmon, sardines, herring, white fish or menhaden.

What is special about omega-3 fatty acids? Omega-3 fatty acids, and in particular EPA and DHA, have important functions in the body. Appropriate amounts of omega-3 fatty acids support normal neural development, the cardiovascular and immune systems, skin and coat health, and reproductive fitness. Increasing omega-3 fatty acids in a dog’s food may also have slight to moderate therapeutic benefit because of their dampening effect upon the body’s inflammatory response. For example, increasing the proportion of omega-3 fatty acids in the diet can aid in the management of chronic joint pain due to arthritis and may reduce itchiness due to allergic skin problems in some dogs. In addition, DHA is important for development of a healthy nervous system and vision in fetuses and newborn puppies (we discuss DHA in detail in our “Puppies to Seniors” course).

Are Commercial Dog Foods a Good Source? A challenge regarding omega-3 fatty acids is that optimal levels to include in dog foods are not well defined and levels found in commercial  dog foods vary enormously. In one study, researchers at the Norwegian School of Veterinary Science measured omega-6 and omega-3 levels of 12 different brands of commercially available products (1). Analysis of the foods showed a wide range of both types of fatty acids. While some foods were almost completely devoid of marine oils and the specific omega-3 fatty acids that they provide, others contained omega-3 fatty acids but primarily in the form of alpha-linolenic acid from plant oils. This is an important finding because often only omega-3 content is reported on the pet food label. If the omega-3 fatty acids are supplied primarily as alpha-linolenic acid, for example from flax, the health benefits that come from EPA and DHA will not be provided by that food.

Do Pet Food Labels Reflect Actual Omega-3 Content? An additional concern is labeling. A recent study, conducted by a group of researchers at the University of Maringa in Brazil, compared the fat content reported on the labels of 10 dry (extruded) dog foods with laboratory-measured profiles of omega-3 fatty acids, DHA and EPA from the foods (2). Results: All 10 foods reported total omega-6 and total omega-3 fatty acid levels and five also included EPA and DHA content on their product label. However, when the researchers measured these fatty acids in food samples, they found a different story:

  • Chicken fat: In all 10 foods, a lipid profile consistent with (and identified to be) chicken fat appeared to be the predominant fat source. Technically, this was not inconsistent with the foods’ labels, as all of the foods did report including chicken fat in their product. However, when graphic representations of the lipid profiles from the foods were compared with the profile of pure chicken fat, results suggested that chicken fat (not fish oil) was the predominant fat source in all 10 products.
  • DHA and EPA: Although five of the 10 foods reported minimum DHA and EPA levels (something they are not required to do), neither DHA nor EPA were present in any of the foods. Conversely, other omega-3 fatty acids were found (including alpha-linolenic acid), leading to total omega-3 fatty acids levels that conformed to label claims. Further analysis showed that none of the lipid profiles of these foods were similar to those for either sardine oil or salmon oil, two primary sources of EPA and DHA in pet foods.
  • Causes? The researchers speculate that the lack of EPA and DHA in the samples could be caused by (1) destruction (i.e. oxidation) of the long-chain unsaturated fatty acids during the heat processing of extrusion or (2) manufacturers of the foods had not included DHA and EPA in the first place. It is worth noting that label claims for fatty acid content are required to reflect minimum levels in the final product (not prior to processing) which negates the plausibility of the first explanation.
  • Authors conclude: The researchers conclude that: “The information displayed on the [commercial dog food] labels are in disagreement with the results obtained for the fatty acid composition analysis……and for lipid profile analysis [in this study].


Well, this all does seem rather fishy (or more fittingly, NOT fishy).

I have written about misbranding of pet foods and label claims problems before (see “What’s in Your Food?” and “What’s in Your (Vegetarian) Food?“). However, this is the first study, to my knowledge, that examines potential discrepancies between label reports of fat content and measured values of fish oil, omega-3 fatty acids and EPA/DHA in commercial dog foods. If it is a dog owner’s intent to choose a food that provides omega-3 fatty acids, this study suggests that reading about these fats, in particular DHA and EPA, on a food’s label may not be reflective of what is actually in the product. (Note: The foods studied in this report were purchased in Brazil. However, the international nature of the pet food industry suggests that at least some of these brands are available in other countries [brands were not identified in the study]).

Take Away for Dog Folks:  So, what is a dog owner to do?

Well, remember that the best source of the long-chain omega-3 fatty acids, DHA and EPA, are algae or fish. If you desire to increase your dog’s intake of long-chain omega-3 fatty acids, look for the presence of fish (salmon, white fish, menhaden) meals or fish oils on the food’s ingredient list. Alternatively if you see no fish products and instead see flax, flaxseed oil, or canola oil high on an ingredient list, this means that the omega-3 fatty acids that are in that food are in the form of ALA, which is important but will not be an enriched source of EPA or DHA.

When in doubt, contact the food’s manufacturer. Ask how (and if) they actually measure DHA and EPA, and ask to see those numbers. Misbranding seems to be a relatively common problem in the commercial pet food industry. One way to combat it is to demand more information and increased transparency from pet food manufacturers. Purchase foods from manufacturers that answer your questions and readily provide you with requested information, that you trust, and that produce honest products with verified label claims.

If you are looking for a food that has increased omega-3 fatty acids and enriched levels of DHA and EPA, remember that there actually should be something a bit fishy about that food.


Cited Studies: 

  1.  Alhstrom O, Krogdahl A, Vhile SG, Skrede A. Fatty acid composition in commercial dog foods. Journal of Nutrition 2004; 134:2145S-2147S.
  2. Silveria R, dos Santos PDS, Pizzo JS, et al. Evaluation of dog food authenticity through lipid profile using GC-FID and ESK-MS. Journal of Brazilian Chemical Society  2020 (in press).

Interested in Learning More about Canine Nutrition? Take a Look at the Science Dog Courses!


3 thoughts on “Does this Seem (not…) Fishy to You?

  1. Pingback: Omega Fatty Acids: Why Sourcing Matters - NorthPoint Pets

  2. Pingback: New Facts about Flax – The Science Dog

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