Confused about Dietary Fats? ……. Good Fats, Bad Fats, Fatty Acids – what is it all about?

by Dr Jennifer Ervin BVSc (Hons) Hill’s Technical Services Veterinarian

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For the purposes of clinical nutrition, dietary fats can be classified as facilitative or functional.

Facilitative fats  

  • improve palatability and increase the acceptable texture of foods
  • are a dense source of energy
  • promote the absorption of fat-soluble vitamins
  • can be found in reasonably large amounts in foods formulated for dogs and cats
  • include dietary saturated and monounsaturated fats


Functional fats

  • participate in important structural or functional cellular processes
  • can be converted to an important derivative that regulates cell function
  • include dietary polyunsaturated fats
  • are fatty acids like linoleic acid, α -linolenic acid, arachidonic acid, docosahexaenoic acid and eicosapentaenoic acid

Functional fats have been “hot” in human and veterinary nutrition fields for a while.  

Why is that?

Well let’s take a closer look at them.

Polyunsaturated fatty acids (PUFA) such as linoleic and α-linolenic acid are essential fatty acids because animals cannot synthesise them and therefore they need to be supplied in the diet.

The two most important (and well known) of the PUFA series are the omega-6 series and the omega-3 series. No doubt you have heard of them.

In the omega-6 series, linoleic acid (LA) is metabolized to eventually form arachidonic acid (AA).

  • Dietary sources of omega-6 fatty acids include vegetable oils, poultry, eggs, nuts, seeds and grains


In the omega-3 series, α-linolenic acid (ALA) can be metabolised to form eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

  • Many marine plants (e.g. algae and phytoplankton) are able to convert α-linolenic acid to long-chain omega-3 PUFAs and thus their transfer through the food chain to fish account for the abundance of EPA and DHA (omega-3 FA’s) in certain marine fish oils
  • Dietary sources of ALA come mainly from plant oils like walnut, clary sage seed and flaxseed oil.  However neither humans, nor our pets, are very efficient at converting ALA to EPA so the best way to get omega-3 fatty acids is from marine fish oils.

The reason for all the excitement is that these fatty acids serve as substrates that are metabolised to form biologically active compounds in the body.  AA (omega-6) and EPA (omega-3) act as precursors for the synthesis of eicosanoids. Eicosanoids are a significant group of immunoregulatory molecules that function as local hormones and mediators of inflammation. The amounts and types of eicosanoids synthesised are determined by the availability of the PUFA precursor and by activities of the enzyme system to synthesise them.

In most conditions, the principal precursor for these compounds is AA, although EPA competes with AA for the same enzyme systems. Eicosanoids produced from AA appear to be more inflammatory than those formed from EPA. Ingestion of oils containing omega-3 PUFA results in a decrease in membrane AA levels since omega-3 PUFAs replace AA in the substrate pool, and also produces an accompanying decrease in the capacity to synthesise eicosanoids from AA. In contrast, eicosanoids derived from EPA induce less inflammatory activity and may alter vascular function.

In recent years, new families of locally-acting mediators were discovered that are biosynthesised from EPA and DHA. These potent lipid mediators, known as resolvins, protectins and maresins, have been shown to control the magnitude and duration of inflammation, and offer the first glimpse of a molecular rationale for the many health benefits attributed to dietary omega-3 fatty acids.1,2

You only have to consult Wikipedia or Google to appreciate that omega-3 fatty acids have long been associated with beneficial effects in human health and in the prevention of various diseases.  The list is long and includes inflammation, immunomodulation, autoimmune diseases, rheumatoid arthritis, cardiovascular diseases, Alzheimer’s disease and other neurodegenerative diseases, type-2 diabetes, and cancer.

Their use and benefits are not restricted to humans alone of course. Our animal friends can garner significant benefits as well from omega-3 fatty acid supplementation for a range of similar applications.  

Many of our Prescription Diets utilise omega-3 fatty acid technology to help improve and lengthen the lives of your patients with different conditions.  For example, take a look at these blogs on j/d, b/d and Derm Defense to learn more.

2.pngJen graduated from the University of Melbourne with honours in 1999.  After graduation Jen worked in mixed animal/dairy practice for a short spell before moving into 100% small animal practice.  In 2002, Jennifer and her now husband Matthew (also a veterinarian), spent two years working in the U.K. This entailed many different small animal veterinary roles including work in an emergency centre, as well as a stint as a greyhound track vet! Since returning to Australia, Jen has worked as a sole charge practitioner in small animal practice, spent a year as a Veterinary Territory Manager for Hill’s and also worked as a Practice Manager of a large mixed animal practice for eighteen months.  Since 2008, Jennifer has worked as a Technical Services Veterinarian for Hill’s Pet Nutrition.


  1. Serhan, Charles N., and Nicos A. Petasis. “Resolvins and Protectins in Inflammation-Resolution.” Chemical reviews 111.10 (2011): 5922–5943. PMC. Web. 2 Aug. 2017.
  2. Ariel A , Serhan CN. Resolvins and protectins in the termination program of acute inflammation: Review. TRENDS in Immunology 2007; 28:176-18