Although dietary fats often get a bad rap, especially in human health, they are a necessary nutrient component of the diet. I recently posted about problems of excessively supplementing pet diets with fish oil and shared the upper dose limit that research indicates is safe when treating many inflammatory diseases. Doses for normal animals are typically ¼ -½ of those doses. But absolute amounts are not the entire story. Dietary fat metabolism is more complicated than that. Today I would like to share some interesting fat factoids.
Without getting too technical, fatty acids are long chains of carbon molecules that are paired, or “bonded,” to hydrogen atoms. Fatty acids that have a single hydrogen atom bonded to a single carbon atom are called saturated fatty acids. Fatty acids which have shared atoms in what are called “double bonds” are said to be unsaturated. If only one double bond occurs in the carbon chain, these fatty acids are called monounsaturated fats. Fatty acids with multiple double bonds are called polyunstaturated fatty acids, or PUFAs.
Omega Fatty Acids
Omega-6 and Omega-3 fatty acids are PUFAs. Their number designation refers to where the double bond occurs in the carbon chain. Both have important roles in cell wall structure and function, and in skin and fur quality. They differ in their role in the immune system. Omega-6 fatty acids are broken down into various signaling molecules called cytokines. These cytokines initiate an active response in the immune system to ward of foreign invasion. Due to their role in the immune response, omega-6 fatty acids are considered “pro-inflammatory."
The cytokines produced by omega-3 fatty acids temper the immune response and are considered “anti-inflammatory” fatty acids. It is this effect that is exploited to treat conditions promoted by an exaggerated immune response (allergies, intestinal conditions, arthritic conditions, etc.) with the omega-3s in fish oil, especially EPA (eicosapentaenic acid) and DHA (decosahexaenoic acid).
Pro-inflammatory and anti-inflammatory responses are important for all animals. The balance of the two systems maintains an ideal internal body environment. That balance is determined by the ratio of dietary omega fatty acids.
An ideal ratio of omega-6 to omega-3 is presently unknown. Research has prompted the National Research Council (NRC) to recommend a range from 2.6:1 to 26:1, which is quite wide. Diets containing 2.6-10:1 are considered anti-inflammatory without affecting the protective “pro-inflammatory” immune response. Excessive supplementation of fish oil that causes the ratio to fall below 2.6:1 can suppress the immune response and clotting function mentioned in the above previous post.
What this means is that the dosing fish oil supplementation for its rich EPA and DHA is dependent on the amount of omega-6 and other omega-3 already in the diet. Even small doses of fish oil supplementation could decrease the 6:3 ratio below recommended if a pet's diet contained only small amounts of omeg-6s or large amounts of other omega-3s. Always consult your veterinarian before dosing supplements.
Seed Oils as Omeg-3 Sources
Flaxseed, rapeseed (source of canola oil) and soy oils are considered high omega-3 fatty acids and good, non-animal substitutes for fish oil as sources of EPA and DHA. That may not be the case.
The omega-3 fats in these seed oils are considered undifferentiated and need to be converted by the body to DHA and EPA. Research in humans, dogs and cats indicate that the efficiency of this conversion is influenced by gender, age, and medical status. The amount of EPA or DHA derived from seed oils would differ for each individual.
Research has also confirmed that seed oil omega-3 is not directly converted to DHA in the liver and other organs. Rather it is converted to DPA (decosapentaenoic acid), a precursor to DHA that must be converted in the retina of the eye and other nervous tissue. The efficiency of this conversion is unknown. This does not mean that seed oils cannot be used as sources of EPA and DHA, but it does mean we cannot predict the dose or the value to the pet.
Fats; more complicated than you thought, eh?
Dr. Ken Tudor