Like humans, animals require optimal nutrition to maintain good health and prevent disease. Not surprisingly, nutritional therapy that focuses on supplementation with essential nutrients has been able to reverse and treat disease. Essential nutrients must be obtained in the diet, since normal metabolic processes are unable to manufacture them. Essential fatty acids (EFAs), once called vitamin F, are amongst the nutrients we know to be essential.
Deficiency of EFAs was first recognized in experimental animals in 1929 by Burr and Burr, who found that animals deprived of certain fats (later recognized to be EFAs) developed growth retardation, skin lesions, organ failure, impaired fertility, and a host of other problems that eventually resulted in death. Since then, research has focused on what the physiological role of fatty acids are and why they are essential; which fatty acids are essential; and how supplementation can promote health and ease disease.
EFAs are structural components of all cell membranes, where they ensure the proper structure and function of all cells. They are also substrates for the enzymes cyclooxygenase (COX) and lipoxygenase, which convert EFAs into eicosanoids. Eicosanoids are physiologically vital, hormone-like compounds that control a myriad of metabolic activities including blood clotting; inflammation; blood pressure; vasoconstriction and vasodilation; and immune function. Ongoing research in the last decade has uncovered even more exciting news – EFAs are able to control cell communication and gene regulation, which ultimately controls all cellular processes ranging from hormone production to cell growth and division. Supplementation with EFAs may therefore provide the means to prevent and treat disease by controlling the “on-off switch” of the disease.
The primary EFAs include the omega-6 fatty acids linoleic acid (LA) and its derivative gamma-linolenic acid (GLA); and the omega-3 fatty acids, alpha-linolenic acid (ALA), and its derivatives eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA). Although all of these fatty acids are essential, diet and metabolic processes dictate which fatty acids should be further supplemented by diet.
LA is one of the major fatty acids found in vegetable oils such as corn, sunflower and safflower oils. ALA is found in substantial quantities in flaxseed, and in flax and perilla oil, and in smaller quantities in other oils such as canola and hemp. The most common sources of GLA are borage, evening primrose, and black currant seeds. Borage oil contains the highest level of GLA (20-25%), whereas black currant oil at 14-17% GLA and evening primrose at 8-10% GLA contain lower amounts. EPA and DHA are obtained from fish and fish oil.
Oils containing EFAs have been extensively studied as therapeutic agents in animals for improving the health of the skin and coat; for relieving dermatological disorders; for reducing inflammation in skin and joints; and for preventing and controlling disease such as obesity and diabetes. The therapeutic efficacy of EFAs is dependent upon the specific EFA as well as the ratio between them.
Essential Fatty Acids and their Function in Skin and Dermatological Disease
Cutaneous (skin) disorders occur frequently in domestic animals such as cats and dogs as a result of abnormal EFA status. The structure and barrier function of EFAs in the skin, as well as the ability of EFA supplementation to regulate epidermal proliferation, cutaneous inflammation, atopic dermatitis, and other skin disorders has been widely demonstrated in cats and dogs. Although not extensively examined in many other animal species, similar results are expected.
The delta-6-desaturase (D6D) enzyme which is required for the conversion of LA to GLA, and ALA to stearidonic acid (which subsequently forms EPA and DHA), may have very low activity or not be active at all. In fact, cats seem to almost entirely lack this enzyme and its activity. Thus, cats depend primarily or entirely upon dietary sources to obtain the fatty acids GLA and EPA for skin and coat health. Diets providing only LA and not longer chain omega-6 fatty acids have been insufficient to provide for normal metabolic processes in cats, leading to growth retardation, poor skin and coat condition, and other problems.
Miliary (crusting) dermatitis in felines is associated with abnormal EFA status and the condition has improved and/or resolved completely after supplementation with evening primrose oil, both alone and in combination with fish oil. Evening primrose oil has also been shown to improve feline papulocrustous dermatitis.
Elevations in transepidermal water loss (TEWL), which may be related to conditions such as pruritis and seborrhoea in animals, have been reversed after topical administration of sunflower oil, which contains high amounts of LA, and borage oil, which contains high amounts of GLA.
Various skin inflammatory conditions have been treated with omega-3 and omega-6 fatty acids in the canine and feline. GLA, EPA and DHA are common supplemental EFAs for inflammation of the skin. Pruritic skin disease has been managed successfully with omega-3 fatty acids, as well as with a controlled omega-6:omega-3 ratio.
Canine atopic dermatitis has been successfully treated with both EPA and GLA. Significant improvements in clinical measures such as pruritis, erythema and inflammation make EFAs one of the most widely used treatments for these types of conditions. Supplementation with EFAs can reduce the need for steroids in animals with atopy.
Both flaxseed and fish oil decrease the skin inflammatory response to histamine, and thus supplementation may be useful for suppressing inflammation due to allergy. EFA supplementation is able to reduce the intradermal test reactivity to allergens in dogs, as shown by a decrease in the number of positive reactions, the mean histamine and the wheal diameter. Additionally, studies in dogs with atopic dermatitis show that EFA supplementation provides a synergistic effect with drugs such as hydrazine and chlorpheniramine, and improves clinical symptoms and control of pruritus.
GLA, EPA and DHA clearly can improve skin and coat conditions in animals and overall dermatological condition and are recognized as therapeutically effective agents for symptoms such as pruritus, scaling, erythema, self-trauma, dryness, and alopecia.
Essential Fatty Acids and Musculoskeletal Disease
As in humans, arthritic conditions in animals also respond favourably to EFA supplementation. A deficit of omega-3 fatty acids has been linked to osteochondrosis, a group of osteoarticular diseases resulting from ossification in the growing animal, that can affect large breed animals such as the Labrador and the German Shepherd. Supplementation with EFAs may prove useful.
Inflammatory bowel disease in dogs, cats and other animals may also respond favourably to supplementation with EFAs.
Growth and Reproduction
Kittens fed diets deficient in fatty acids derived from delta-6-desaturation, such as GLA and EPA, have abnormal growth patterns and metabolic rates, demonstrating the importance of the products of delta-6-desaturation for felines.
Animal studies indicate that essential fatty acids of both the omega-3 and omega-6 series, and their eicosanoid metabolites, play important and modifiable roles in gestational duration and parturition, and omega-3 fatty acid intake during pregnancy may be inadequate. Prostaglandins (PGs) of the 2-series are involved in parturition and connective tissue remodelling associated with cervical maturation and rupture of membranes. Preterm birth is characterized by lower reproductive tissue PG production and decreased inducible cyclooxygenase expression. Supplementation with omega-3 fatty acids may significantly reduce the incidence of premature delivery and increased birth weight associated with increased gestational duration. Supplementation with long chain omega-3 fatty acids such as docosahexaenoic acid may be useful in prolonging the duration of gestation in some high-risk pregnancies.
Feed Efficiency and Addition of EFAs into the Food Supply
Deficiencies of EFAs can negatively impact animal production and feed efficiency. Dairy cows fed a diet enriched with GLA have a higher fat content in their milk, in addition to a slightly higher milk yield. The addition of GLA in the diet of dairy cows could also be considered a biologically active additive that may provide numerous health benefits. The milk obtained may bear a closer resemblance to human milk, which contains GLA.
Essential fatty acids such as GLA and DHA have also been added to the feed of domesticated birds such as hens. This may improve egg production, increase egg size, or increase the proportion of EFAs in the eggs. Research has shown that omega-3 fatty acids have beneficial effects on cardiovascular health, such as decreasing atherogenesis and blood platelet aggregation. Overall studies on omega-3 enriched eggs are overwhelmingly positive, with three omega-3-enriched eggs providing approximately the same amount of omega-3 fatty acids as one meal with fish.
Essential fatty acids and Cancer
Polyunsaturated omega-3 fatty acids have been gaining attention in the research community for their effects on cancer and cachexia. Notably, they have been shown to inhibit the growth and metastasis of tumors. Lymphoma in dogs has been among the types of cancer studied.
Essential Fatty Acids and Cardiovascular Disease
Fish oil may be a useful non-drug treatment for dogs and cats with congestive heart failure, and has been shown to decrease myocardial infarct size in models of ischemia and reperfusion, as well as provide protection against ischemia-induced fatal ventricular arrhythmias in models of sudden cardiac death.
Canine symmetrical lupoid onychodystrophy (symptoms included onycholysis, onychomadesis, onychalgia and onychodystrophy) have been shown to respond to EFA supplementation.
Formation of cholesterol crystals and gallstones in the prairie dog has been inhibited through supplementation of fish oil in the diet.
As in humans, certain EFAs may be useful in the management of other diseases, including diabetes, obesity, and immune system dysfunction.
Essential fatty acid deficiency can occur in animals that are fed dry rations, poorly preserved commercial food (storage, temperature, preservative problems) or homemade foods. Deficiencies may occur because the fat content is low, because the fat became rancid, or because there is inadequate antioxidants such as vitamin E in the food. Medical conditions that limit the animal’s ability to absorb or metabolize ingested fats can also result in EFA deficiency. Symptoms of deficiency occur over time and skin problems are a particularly common occurrence.
Essential fatty acid intake has long been recognized as playing an important role in animal, as well as human, health. Various skin and inflammatory disorders, cardiovascular problems, mental dysfunction, cancer and numerous other disorders and diseases have been attributed to abnormal EFA status and deficiency of certain fatty acids, notably GLA, ALA, EPA and DHA. Ongoing research has identified the profound positive effects supplementation can provide to help maintain health, as well as prevent and treat disease.
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