Essential Oils

David McCluggage, D.V.M., C.V.A.

There are a number of different fatty acids which can be roughly divided into saturated fatty acids (solids at room temperature, animal source) and unsaturated fatty acids (vegetable fats that are liquids at room temperature). Saturated fatty acids have been linked to heart disease and other disorders in people, although their role in animals is not as clear. It seems likely that carnivores should process saturated fats better and not suffer the adverse effects (heart disease, atherosclerosis) seen in man. Unsaturated fatty acids are actually cardioprotective and decrease the incidence of neoplasia.

Essential fatty acids are required in the diet, as they cannot be produced in the body. There are two essential fatty acids in people, linoleic acid (O-6) and alpha-linolenic acid (O-3). Dogs and cats can't convert O-3 to O-6 or the opposite. Thus, linoleic acid (O-6) and alpha-linolenic acid (O-3) are essential in the dog and cat.

Arachadonic acid is required in the diet of cats [i] , and can only be acquired from animal fat sources. Cats do not produce delta_6_dehydrongenase, the enzyme required to convert alpha-linolenic acid to eicosapentaenoic acid (EPA), so if one wishes to increase the amount of EPA, it is best to supplement with omega 3 fatty acids, such as those found in cold water fish oils. Salmon, menhaden and mackerel oils, for example, all contain large amount of EPA and docosahexaenoic acid (DHA). Even in humans, only 10% of flax ALA is converted to EPA. This would suggest that your flax dose be 10X your fish oil dose, if you have fixed doses. I use only salmon or menhaden oil. Linoleic acid's first double bond (i.e. unsaturated bond) is located at the sixth carbon, thus it is called an omega 6 fatty acid. Alpha-linolenic acid's first unsaturated bond is at the third carbon, thus it is called an omega 3 fatty acid. They are necessary constituents of cell membranes, for the synthesis of prostaglandins and related compounds, and in nurturing the skin. They are also required for reproduction, normal hair and feather development, and wound healing [ii] . There are two other naturally occurring fatty acids of less significance, omega 7 and omega 9 fatty acids, as the body can synthesize these.

In people, the diets are shifted heavily in the direction of the omega 6 fatty acids, resulting in tissue levels of omega 6's at 20:1 over omega 3 fatty acids. Animal diets are probably similar, as omega 3 fatty acids have a much greater average cost factor. This is significant in that the different fatty acids produce different prostaglandins and perform different functions in the body. People should have tissue ratios of 4:1 omega 6 to omega 3 fatty acids for optimal health. This may be similar in animals, but has not been proven.

In general, omega 3 fatty acids reduce the inflammatory response and omega 6 fatty acids enhance inflammation. Since omega 3 fatty acids are more limited in the diet, it is easier to see beneficial effects from their supplementation. Additionally, desaturase enzymes (which elongate and desaturate fatty acids, thus converting them to different ones) have a greater affinity for omega 3 fatty acids, so increasing the amount of omega 3 fatty acids will decrease the amount of omega 6 fatty acids. Benefits of omega 3 fatty acids include:

  1. Inhibition of tumor development and tumor metastasis [iii]
  2. Lowering of cholesterol levels, modifying platelet and vascular function, heart disease therapy
  3. Improving arthritis
  4. Relief of allergic symptoms, eczema and psoriasis
  5. Diminish the inflammatory response

Of particular significance for this discussion on the omega 3 fatty acids is eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are derived in the largest amounts from cold-water fish oils. EPA seems to be a potent inhibitor of the inflammatory cascade, as it is a regulator of enzymes that control the pathway of omega 6 fatty acids to eicosanoids. EPA also inhibits delta_5_desaturase and thus decreases arachidonic acid production in the dog and man, but not the cat. The arachidonic acid pathway produces leukotrienes and prostaglandin E_2 (PGE_2), which produce inflammation. EPA has been shown to:

  • Improve allergies in people, through modulating the humoral and inflammatory components of the allergic response [iv]
  • Help relieve the symptoms of canine atopic dermatitis [v]

These inflammatory prostaglandins (PGE-2) are often considered the "bad" ones, but this is not accurate, as they do play an important role in the body's healing process. The inflammatory response should not always be inhibited, and many cases actually need omega 6 fatty acids to promote the inflammatory response. One popular fatty acid that can play this role is gamma linoleic acid (GLA). GLA has been shown to inhibit the activity of Natural Killer Cells, promote the Arachadonic pathway and produce PGE-2 and leukotrienes. It will also increase delta 6-desaturase activity, an enzyme often missing in dogs and people with atopy.

Many nutraceutical manufacturers produce products that have combinations of omega 3 and 6 fatty acids, often presented in the 4:1 ratio as previously mentioned. These combination products may allow the body to regulate the levels of prostaglandin E-1 and E-2 and other components of the inflammatory response, thus allowing for proper healing to take place.

Some people think that flax seed oil is the best source of fatty acids as it has a relatively low level of saturated fats (9% of the total fat content), smaller amounts of linoleic acid (14 % of the total fat content, an omega 6 fatty acid), and high amounts of alpha linolenic acid (58% of the total fat content, an omega 3 fatty acid). This is due primarily because the cost is so much less than giving a more pure omega 3 supplement such as cold-water fish oils, and to the fact that the omega 6 oils are in relatively small amounts. However, most manufacturers actually mix fish oils, flax oil, borage oil, and a vegetable oil such as safflower oil to achieve the 4:1 ratio, and thus give the body the building blocks to produce either inflammation enhancing or inhibiting prostaglandins. This allows the body to decide which direction it needs to go with its own system of regulating inflammation.

If the condition being treated is primarily one of inflammation (e.g. arthritis or dermatitis), it is likely that omega 3 fatty acids would be indicated. There is evidence, as well, to support the use of omega 3 fatty acids in the treatment of neoplastic conditions [vi] .

Here is a brief summary of the type of oils found in different products:

Omega 3 fatty acids predominate:

Fish Oils

Omega 6 fatty acids predominate:

Vegetable oils


Evening primrose oil (GLA and linoleic acid)

Omega 6's predominate, but omega 3 present in significant amounts (but, NOT eicosapenaenoic acid:


[i] MacDonald , ML, et al. Nutrition of the domestic cat, a mammalian carnivore. Ann Tev Nutr, 4:562, 1984.

[ii] Lewis, LD, Morris, ML, Hand, MS. Small Animal Clinical Nutrition III. Mark Morris Associates, Topeka, KS, 1987, p 1-18.

[iii] Ramesh, G. et al. Effect of essential fatty acids on tumor cells. Nutrition. 8:343-347.

[iv] Lee, TH, Arm, JP. Modulation of the allergic response by fish oil lipids and eicosatrienoic acid. Prog Clin Biol Res. 297:57-69, 1989.

[v] Logas, D. Double blind crossover study with high dose eicosapentaenoic supplementation for the treatment of canine allergic pruritic. Proceedings of the Am Academy of Vet Dermatology. 1993.

[vi] Daly, JM. et al. Enteral nutrition with supplemental arginine, RNA, and omega 3 fatty acids: A prospective clinical trial. Abstract, 15th Clinical Congress, Am Soc for Parenteral and Enteral Nutrition, JPEN 15:19s, 1991.