Sales of human omega-3 fatty acid supplements are projected to show a staggering compound annual growth rate (CAGR) of 13.1% over the next five years, with the global market reaching US$8.5 billion by that time, according to MarketsandMarkets.

The potential of omega-3 fatty acid consumption to positively influence health has been an active field of research for four decades. Four omega-3-based human prescription drugs for the control of elevated triglyceride levels have even been approved by FDA. People are increasingly becoming aware of the importance of omega-3 intake to support areas such as the cardiovascular, nervous and immune systems, as well as brain and eye development in infants. It is also a well-recognized phenomenon that people tend to want to extend the benefits of supplements they use to their pets.

The medium-chain omega-3 polyunsaturated fatty acid (PUFA) alpha-linolenic acid (ALA) is considered an essential nutrient in the human diet; essential meaning it must be present in the diet because the body cannot synthesize it. The longer-chain omega-3s docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are synthesized  in the body from ALA, but the rate of conversion is low, leading to speculation that DHA and EPA should be considered conditionally essential—required in the diet for circumstances that call for higher levels.  The only other essential fatty acid (EFA) in humans is the omega-6 linoleic acid.

Canine considerations

The situation in dogs is not as clearly defined. The omega-6 requirement has been set at 3.3 g/1,000 kcal of diet for puppies and 2.8 g/1,000 kcal for adult dogs. However, while the National Research Council has set tentative targets of ALA 0.2 g/1,000 kcal for puppies, 0.11 g/1,000 kcal for adult dogs with DHA + EPA combined 0.13 g/1,000 kcal for puppies and 0.11 g/1000 kcal for adult dogs, this has not been adopted in recommendations for pet food manufacturers.

Both the Association of American Feed Control Officials [AAFCO] and the European Pet Food Federation [FEDIAF] recognize health benefits of omega-3 fatty acids, but do not feel there is sufficient information available to establish a dietary requirement for adult dogs. As a result, there is currently no requirement for pet foods to contain omega-3, even when labeled “complete and balanced.”

Given the very low omega-3 levels in grains, grain-fed animals, vegetable matter and vegetable oils—plus the fragility of omega-3 acids—the canine intake of these important fats in dogs on commercial diets is very low.  Contrast this with the intake of their feral ancestors, the wolves.

When sufficient prey exists, the diet of wolves is approximately 70% large herbivores such as elk, deer, moose and wild oxen. They will also consume smaller herbivores like beavers or rabbits, and some mice.

This natural diet will contain from 20% to 40% fat, while commercial kibble may be as low as 5%. The ratio of omega-6 to omega-3 fatty acids in range-fed herbivores (no grain) is around 3:1, while grain feeding shoots this up to a whopping 17.2:1.

Canine studies

Research has helped clarify the roles omega-3 fatty acids play in canine health. Skin and coat quality is a readily observed marker of health and was one of the first areas where veterinarians experimented with supplementation. A randomized, double-blind, placebo control study documented both enhanced skin and coat condition and the incorporation of supplemental DHA and EPA into cell membranes.¹

Addition of fish oil or krill oil to canine cartilage explants was shown to downregulate the expression of genes coding for the catabolic, tissue-destroying matrix metalloproteinase enzymes.² The benefit to joints has been confirmed in vivo in a high quality, randomized, double-blind, placebo-controlled study using DHA and EPA supplementation.³

Cognitive dysfunction syndrome (CDS) in aged dogs is believed to be analogous to senile dementia/Alzheimer’s disease in humans. DHA depletion is part of the picture in Alzheimer’s disease, with associated chronic inflammation. Fish oil supplementation in combination with B vitamins and antioxidants has been shown to improve cognition in senior dogs.⁴ As in other species, DHA is crucial to normal development of the brain in young dogs, with evidence of improved memory and learning.⁵

Omega-3 supplementation of bitches has been shown to improve retinal function in young puppies.⁶ Interest is also growing in the cardiovascular benefits of omega-3 fatty acids. Freeman stated: “Omega-3 fatty acids' anti-inflammatory and anti-arrhythmic effects may be beneficial in managing the loss of lean body mass and arrhythmias that are common in heart failure.⁷ However, omega-3 fatty acids also may have positive effects on myocardial energy metabolism, endothelial function, heart rate and blood pressure.”

Omega-6:3 ratio matters

As clearly demonstrated in the human studies, the ratio of omega-6:3 is important. When diets conform to the current recommended intakes, the ratio is 25:1. When dogs are fed a diet with a 5:1 ratio, much closer to what a grass-fed carnivore diet would supply and believed to be a more healthful level for humans, there are clear benefits in terms of more robust innate immune system responses and improvement in some oxidative stress markers.⁸

Omega-3 Sources

As with humans, debate exists regarding whether supplementing the plant-based ALA precursor of DHA and EPA such as flax oil is adequate, or if supplementation should be with preformed DHA and EPA from fish oil or krill oil. It's true that ALA supplementation does not automatically increase serum DHA and EPA levels, but a rational explanation for this is that DHA and EPA production occurs on an as-needed basis, as supported by the Dunbar study, “Early and sustained enrichment of serum n-3 long chain polyunsaturated fatty acids in dogs fed a flaxseed supplemented diet.”⁹

Unless the immediate benefits of preformed DHA and EPA from fish oil is indicated, a blend of high-ALA flaxseed oil with fish oil is appropriate for dogs. When the diet is low in fat overall, the addition of a good omega-6 source for a final ratio in the supplement of close to 1:1 will help to balance out the omega-6 predominance in commercial diets.

Eleanor Kellon, VMD, staff veterinary specialist for Uckele Health & Nutrition, is an established authority in the field of equine nutrition for over 30 years, and a founding member and leader of the Equine Cushings and Insulin Resistance (ECIR) group, whose mission is to improve the welfare of horses with metabolic disorders via integration of research and real-life clinical experience.

References

1 Combarros D et al. “A prospective, randomized, double blind, placebo-controlled evaluation of the effects of an n-3 essential fatty acids supplement (Agepi® ω3) on clinical signs, and fatty acid concentrations in the erythrocyte membrane, hair shafts and skin surface of dogs with poor quality coats.” Prostaglandins Leukot Essent Fatty Acids. 2020;159:102140.

2 Buddhachat K et al. “Effects of different omega-3 sources, fish oil, krill oil, and green-lipped mussel against cytokine-mediated canine cartilage degradation.” In Vitro Cell Dev Biol Anim. 2017;53(5):448-457.

3 Mehler SJ et al. “A prospective, randomized, double blind, placebo-controlled evaluation of the effects of eicosapentaenoic acid and docosahexaenoic acid on the clinical signs and erythrocyte membrane polyunsaturated fatty acid concentrations in dogs with osteoarthritis.” Prostaglandins Leukot Essent Fatty Acids. 2016;109:1-7.

4 Pan Y et al. “Cognitive enhancement in old dogs from dietary supplementation with a nutrient blend containing arginine, antioxidants, B vitamins and fish oil.” Br J Nutr. 2018;119(3):349-358.

5 Heinemann KM, Bauer JE. “Docosahexaenoic acid and neurologic development in animals.” J Am Vet Med Assoc. 2006;228(5):700-705,655.

6 Bauer JE et al. “Retinal functions of young dogs are improved and maternal plasma phospholipids are altered with diets containing long-chain n-3 polyunsaturated fatty acids during gestation, lactation, and after weaning.” J Nutr. 2006;136(7 Suppl):1991S-1994S.

7 Freeman LM. “Beneficial effects of omega-3 fatty acids in cardiovascular disease.” J Small Anim Prac. 2010;51(9):462-470.

8 Kearns RJ et al. “Effect of age, breed and dietary omega-6 (n-6): omega-3 (n-3) fatty acid ratio on immune function, eicosanoid production, and lipid peroxidation in young and aged dogs.” Vet Immunol Immunopathol. 1999;69(2-4):165-183.

9 Dunbar BI et al. “Early and sustained enrichment of serum n-3 long chain polyunsaturated fatty acids in dogs fed a flaxseed supplemented diet.” Lipids. 2010;45(1):1-10.