Polyunsaturated fatty acids (PUFAs) are showing up everywhere – in foods, supplements and even joint cream.1 At least one prescription dog food contains more omega-3 content than even nutraceuticals provide. Navigating successfully among the many supplementation options requires understanding the unique attributes of each fatty acid and deciphering the alphabet soup of acronyms.
Where to Find PUFAs
Naturally occurring fats fall into three categories – saturated, monounsaturated and polyunsaturated. (“Trans” fats occupy a separate category of hydrogenated fats created by food processors.) Saturated fats include beef and dairy fat while monounsaturated fats arise from plants such as olive and canola. PUFAs include omega-3 and omega-6 fatty acids. Fish, walnuts, flaxseed and hemp seed contain omega-3s whereas safflower oil, corn oil, peanuts and soybean oil have omega-6’s.
PUFAs produce bioactive molecules known as eicosanoids. Leukotrienes, prostaglandins and thromboxanes derived from omega-3s predominantly afford anti-inflammatory and platelet-inhibiting effects, whereas omega-6s do the opposite.
The ideal ratio of omega-3 to omega-6 fatty acids in carnivore diets remains unclear.
Given that the “typical Western diet” exhibits an unhealthful high omega-6 and low omega 3 ratio, augmentation of omega-3s seems advisable. Further, food grown today contains less omega-3 and more omega-6 fatty acids than in the past.2 Shifting the diet to weight omega-3s more heavily may counter the development of a range of inflammation-based illnesses, including arthritis3 , heart disease and cancer4.
Alpha linoleic acid (ALA) occurs from leafy vegetables, nuts and oils. Major sources include hemp, canola, soybean, flaxseed oil and English walnuts.
Plant-derived PUFAs require desaturation to form EPA and DHA. Several factors such as species, sex, competition for the desaturase enzyme by linoleic acid, and negative feedback inhibition of desaturase by pre-existing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), influence the rates of ALA conversion.5 One source estimates that less than 10 percent of ALA becomes EPA and DHA.6
Fish oils already contain EPA and DHA, and as such, require no conversion. Yet, the fishy odor of the oils, as well as the patient, can limit their acceptability as a supplement.
EPA and DHA appear in recommendations for cancer, cardiovascular health maintenance and nutritional support for repair of brain tissue after traumatic brain injury.7 The gray matter of the brain, the retina and the heart all use DHA as a major structural component. Thus, DHA specifically plays an important role in eye and brain development.
Following desaturation, gamma-linolenic acid (GLA) produces arachidonic acid (ARA), though levels of the required enzyme delta-6-desaturase may vary across species.8
GLA has received research scrutiny for treatment of atopic eczema, rheumatoid arthritis, multiple sclerosis, schizophrenia and pre-menstrual syndrome in humans. A limited number of plants contain abundant GLA concentrations, with evening primrose and borage being the most notable.
Arachidonic Acid (ARA):
ARA supplies the most abundant source of PUFA in the body, providing membrane phospholipids and, as such, precursors to a panoply of molecules such as prostaglandins and leukotrienes that participate in lipoprotein metabolism, platelet activation, leukocyte properties and blood rheology.9 ARA works with DHA in brain development, making it less surprising that breast milk contains rich quantities of both PUFAs. Egg yolks, mammal meat and liver offer abundant amounts of ARA.
What They Do
Research confirms that fatty acids improve health in many ways, including providing flexibility, fluidity, and selective permeability properties to cell membranes.10 A common mechanism by which they do pertains to its anti-inflammatory effects. Lipid mediators derived from omega-3 PUFAs participate in the reduction and active resolution of inflammation.11
Some dogs consuming large quantities of fish oils will exude a fishy odor. Other than that, no adverse effects from supplementing fish oil has been reported in veterinary patients. Humans who consume 1 gram to 3 grams of fish-derived omega-3 fatty acids complain of gastrointestinal upset, fishy aftertaste, elevated blood glucose in patients with diabetes and impaired glucose tolerance, and elevated LDL-C levels in patients with hypertriglyceridemia.12
Ingesting certain fish or shellfish may lead to higher tissue levels of omega-3 fatty acids,14 but it comes at a price. Fish often contains contaminants, depending on species and source. In addition to mercury, toxins range from polycholirinated dibenzo-p-dioxins, furans, polychlorinated biphenyls, polychlorinated naphthalenes and hexachlorobenzenes to arsenic and more.15 Microbial sources of PUFAs are considered non-pathogenic and non-toxigenic.16
There is some concern that fish oils may lead to a heightened risk of bleeding by inhibiting platelet activation and lowering plasma levels of coagulation factors.17 Human reports tie prolonged coagulation times to combining omega-3 fatty acids with warfarin.18
However, an expert opinion assessing the evidential support on this issue dismissed these concerns as insignificant.19
Finally, omega-3 fatty acids may influence the bioavailability of lipophilic medications such as cyclosporine, causing levels to rise.20
1. Kraemer WJ, Ratamess NA, Anderson MJ, et al. Effect of a cetylated fatty acid topical cream on functional mobility and quality of life of patients with osteoarthritis. J Rheumatol. 2004;31:767-774.
13. US Department of Health and Human Services AfHRaQ. Effects of omega-3 fatty acids on cardiovascular disease. Evid Rep Technol Assess. (Summ). 2004;1-8. Cited in: DeFilippis AP and Sperling LS. Understanding omega-3’s. Am Heart J. 2006;151:564-570.