Something To Chew On!

Omega Fatty Acids

By Bernard P. Pukay, DVM.

The importance of essential fatty acids in canine and feline nutrition has been known for some time. Their use as a dietary supplement to improve the health and appearance of the skin and haircoat has been well documented. By contrast, their use in the management of dermatological disorders, particularly their anti-inflammatory and antipruritic effects, continue to be the subject of both ongoing research and lively debate.

Fatty acids consist of a series of carbon atoms that are connected to each other by either a single or a double bond, with a carboxyl group at one end of the chain and a methyl group at the other. Fatty acids with two or more double bonds, are termed "polyunsaturated fatty acids" (PUFA). Polyunsaturated fatty acids include two important series of fatty acids called the omega-3 series (n-3) and omega-6 (n-6). Because neither the omega-3 nor omega-6 series can be synthesized by dogs and cats, they must be supplied in the diet and are therefore termed "essential". Common dietary sources of omega-6 fatty acids include safflower, soy and corn. Sources of omega-3 fatty acids include cold water marine fish and mammals, flax and soy.

Essential fatty acids (EFAs) have a number of important functions in the body, especially in maintaining normal skin structure and function. They are part of the phospholipid layer of the cell membrane, and are also responsible for keeping the skin soft and pliable and adding luster to the haircoat. EFAs also help regulate keratinocyte differentiation and desquamation.

Linoleic acid (18:2n-6) and linolenic acid (18:3n-3) are essential fatty acids for both cat and dog, as well as arachidonic acid (20:4n-6) for the cat. Linoleic acid is particularly important because it alone provides the necessary conditions to facilitate the water permeability functions of the intercellular lipid bilayer of the skin.

The role of EFAs in the inflammatory process has been well documented. The degree of inflammation appears to be determined by the relative amounts of omega-3 and omega-6 fatty acids. Too much omega-6 fatty acid may be pro inflammatory while relative increases in omega-3 results in less inflammation.

Dogs are able to synthesize all essential fatty acids from dietary linoleic acid which is usually provided in canine diets. While canned and moist diets usually have adequate levels of linoleic acid, levels may fall below optimal requirements in commercial dry foods because of rancidity due to improper or prolonged storage or inadequate levels of antioxidants. To avoid this, dry foods should be stored properly.

Cats require linoleic and arachidonic acids in their diet and most commercial feline diets provide adequate levels to meet their requirements. As is the case with canine dry diets, the amount of linoleic acid may fall below adequate levels if the diet is improperly handled.

The use of fatty acids as antipruritic and/or anti-inflammatory agents, particularly for atopic disease and chronic pruritis, has been studied extensively in both dogs and cats. Commercial supplements may contain alpha-linoleic acid (sources: evening primrose, borage seed, black currant oils) and/or eicosapentaenoic acid (EPA)(sources: cold water marine fish oil).

In allergic pruritis, 20% of dogs and 50% of cats may experience alleviation in the clinical signs of pruritis with fatty acid supplementation. Results may be dose dependent, with enhanced efficacy noted in some cases when dosage levels were increased 2-10 times the recommended dose. Duration of treatment may also play a role. While most dogs and cats may show a favorable response to fatty acid supplementation within 2-4 weeks, some patients may require a therapeutic trial lasting 9-12 weeks. Similarly, failure to respond to one supplement does not preclude a favorable response to another product.

Recent studies have shown a synergistic effect when fatty acid supplementation is used in conjunction with antihistamine or glucocorticoid therapy. Synergistic therapy resulted in an increased efficacy rate when combined with antihistamines. There is also clinical evidence to suggest that decreased levels of glucocorticoids are required to reduce pruritis if concurrent fatty acid supplementation is administered.

Still controversial is the determination of the optimal levels of omega-3 and omega-6 fatty acids and the correct ratio of omega-3 to omega-6. A recent study determined that a canine diet containing an omega-6:omega-3 ratio of 5:1 to 10:1 proved optimal for the management of inflammation. Determining which fatty acid supplement is ideal is made difficult because the levels of omega-6 to omega-3 fatty acids in dogs and cats can vary widely depending on the amount of fatty acids consumed in the diet. Clinical response may be the only way of determining which fatty acid supplement is most effective in clinical practice.