Fish Oils, Lipids, Antioxidants.. Oh My!
with Savannah Welna of FeedThyDog, Nutrition Advocate

Today we are going to talk about the ever-so-controversial topic of fish oil. Either hailed as the king of curing all inflammation ailments or as the evil, free radical filled villain. Which is it? Or perhaps, it is neither.


First, fats are complex. They can be enormously difficult to understand. Let’s start with a crash course in fats pertaining to dogs.


Fat has many functions. Fat:


  1. Protects organs
  2. Surround nerve fibers
  3. Make up the phospholipid layer of cells
  4. Needed for bile salts
  5. Needed for the absorption of fat soluble vitamins
  6. Needed for hormones
  7. Provides energy
  8. Increases palatability of food
  9. Provides essential fatty acids- such as omega 3 and omega 6.


Polyunsaturated fat, monounsaturated fat, and saturated fat


Fats can be categorized as simple lipids, compound lipids, and derived lipids. For the article, simple lipids in the form of triglycerides is relevant. Triglycerides include saturated fats, monounsaturated fats, and polyunsaturated fats. The essential fatty acids are polyunsaturated fats.


These names are given to these fats based upon their structure. We won’t go too far into chemistry here, but it is important to understand. Saturated fats are saturated in hydrogen. They are very stable and stack neatly. Animal products are typically rich in saturated fats. Butter is rich in saturated fat and is a solid at room temperature. The fats stack nice and neatly on top of each other. They make up the majority of most dogs’ diets.  See here a picture of a saturated fat vs. an unsaturated fat.


Polyunsaturated fats are the essential fatty acids. They are very fragile. 


Unsaturated fat has one or more double bonds- which basically just means it is not saturated in hydrogen. Polyunsaturated fat is very rich in brain (so if you feed brain, you are adding a lot of polyunsaturated fat) and also makes up many cellular membranes. Polyunsaturated fats are more fragile because they can “break” easier. Polyunsaturated fats have multiple double bonds. When these fats “break,” they start destroying other molecules to stabilize themselves. Here comes the role of antioxidants. Vitamin E (while partnering with other nutrients) help stop this chain reaction and creates a less harmful (but not perfect) molecule.  Therefore, more polyunsaturated fat means a higher dietary requirement for Vitamin E. Also, because they are so fragile and prone to oxidation, commercial dog foods are often not a great source of these fats.


Hang in there. We are almost done with the technical jargon. So the essential fatty acids are polyunsaturated fats. However, they are, well, essential. Not enough of these essential fatty acids will negatively affect coat health, skin health, wound healing, and become particularly important for growing animals. We know that optimal essential fatty acid intake positively affects the brain in growing puppies. You might say that the essential fatty acids are precious, yet quite perilous. 



Omega 3 and 6 from plants vs animal sources


One more thing- we need to know the different forms of the essential fatty acids. We most commonly see for omega 3 ALA (alpha-Linolenic acid), EPA (Eicosapentaenoic Acid), and DHA (Docosahexaenoic Acid). ALA comes from plant sources- such as flaxseeds. EPA and DHA come from animal sources, like eggs, dark meat on chicken, fish, and fish oils. The dog has to convert ALA to DHA. Unless there is an allergy, it is best to feed the performed essential fatty acids- EPA and DHA. For omega 6, we commonly use LA (linoleic acid) and AA (arachidonic acid). Both LA and AA can be found in animal products. Dogs need more omega 6 than omega 3. Contrary to popular belief, omega 6 and omega 3 are BOTH required for proper immune response. Omega 6 deficiency can cause similar symptoms as omega 3 deficiency. 



The essential fatty acids often compete in metabolism


Finally, we need to understand that omega 3 and omega 6 can compete at certain points. If the dog is on a plant based diet, we have to carefully balance the omega ratio. However, if you feed performed essential fatty acids, the ratio becomes less important because they are not competing. The final piece technical jargon I have highlighted the essential fatty acids for omega 3 and omega 6 you likely are most familiar with. It is very, very possible to feed too much fish oil to and as a result interfere with omega 6 metabolism. This can result in worsening coat health. See here where LA competes with ALA and AA with EPA but preformed essential fatty acids do not compete.



Are fish oils all rancid?


Let this be clear: All the essential fatty acids oxidize. Whether in or outside of the body. Many claim that all fish oils are bad because they are rancid. Certainly, there are bad fish oils on the market. However, there are good ones as well. There are downsides of feeding oily fish (such as pollution) every day. There is a benefit to feeding high quality fish oils that test for pollutants- and not all are horrible for the environment. Some claim that algae oils are better for this reason. However, algae oils still oxidize. Unless they are handled as carefully as fish oils, they can be rancid as well. They can also be harder to dose but are a viable option for dogs with allergies. Oils from plants have less double bonds and are a bit more stable. 


Polyunsaturated fat increases need for antioxidants


For reasons stated above, polyunsaturated fat (PUFA) increases need for antioxidants. The dietary requirement for antioxidant vitamin E is directly correlated with PUFA amounts in the diet. However, it does not stop there. The entire antioxidant defence system will eventually require manganese, vitamin C (dogs make this normally in sufficient amounts), protein, and selenium. So it is important to not carelessly dose fish oils. If you would like to learn more about this process from a human nutritionist, I recommend this free course here. Make sure you don’t apply everything to dogs.


How to dose fish oils


There is NO straightforward guide to dosing fish oils because how much fish oil you feed heavily depends on what is already in the diet. A raw diet with oily fish will require none or very little compared to a kibble diet. Moreover, fish oils will have varying levels of epa and dha in them. Of course, it is also important to consider how much omega 6 is already in the diet. Therefore, the suggested feeding on the labels may or may not be accurate. Fear not, if you are reading this, I can help you in the comments dose fish oil. If you need help, state the dogs breed, age, current and ideal weight, current food, and specific fish oil product if you have one.


How to dose vitamin E


For reasons above, there is not straightforward guide to this. However, a generally safe dose is 25-50 IU for toy breeds and small dogs. 50-100 IU for medium dogs. 100-200+ for large and giant breed dogs. This typically covers the needs of reasonable fish and fish oil feeding. This is when using d-alpha-tocopherol NOT dl-alpha-tocopherol (not recommended). Mixed tocopherols are preferred. A vitamin E lesson coming soon :) One other thing, most fish oils that have vitamin E in it have the vitamin E to preserve the product. It does not count as a dietary source of vitamin E for your dog. Therefore, vitamin E still needs to be provided.


Fish oil as an anti inflammatory


Fish oils are often fed in high amounts with raving reviews. Fish oils, high in EPA, will change the cellular membrane and interfere with normal cell signalling. Side effects however can include the same side effects as NSAIDs! This is not to say that this pharmacological approach is never appropriate, it just means that it should only be applied when absolutely necessary and not as a band aid solution. See the previous post Feeding X for Y. 


Fish liver oils


Fish liver oils are different than fish body oils. The most common is cod liver oil. Cod liver oil is very rich in vitamin A and D. You should not add this to kibble without the help of a nutritionist and you should be very careful when adding this to raw diets with organ meats. Also, a lot of cod liver oils are fortified with high amounts of vitamin D that are not appropriate for dogs.


I personally recommend Green Pastures Fermented Cod Liver Oil with Butterfats for Vitamin A, D, and K2. It is a high quality supplement. Again, get help dosing if you find yourself needing to use liver oils. 


Sum it up!



Fish oils can be useful when we cannot provide enough preformed omega 3 in the diet. Not all fish oils are rancid. Too much fish oil can interfere with omega 6 and decrease coat health. Fish oil increases the dietary need for vitamin E and other antioxidants. How much fish oil that is required for each dog is dependent on their age and what they are already eating. Fish oil is often most beneficial in processed diets where fresh meat, organs, and oily fish are not fed or where oily fish is being rotated out. Fish oil can also be used in a pharmacological approach, but should not be the first tool that is reached for. The essential fatty acids are essential- but not in large amounts.