Fish Oil for Dogs: The Scary Truth

By JoAnna Pendergrass / August 13, 2018

What is Fish Oil

Fish oil is the oil derived from the tissues of oily fish. The oil is rich in omega-3 fatty acids, which have proved to be very important for the body.

However, as more information emerges, experts are finding that fish oil may not be all that it’s talked up to be. In fact, fish oil may actually be causing more harm than good.

So why are so many people still purchasing the product? Is there another way to get the benefits of fish oil and those necessary omega-3s??

Let’s get started! 

What are Essential Fatty Acids

From cod liver oil to salmon oil, fish oil itself has been a craze that gained a lot of popularity in the 1990s because of the overwhelming desire for low-fat diets (which we know now wasn’t the best trend to follow).

In fact, scientists quickly discovered that low-fat diets can be very detrimental to our health. We need healthy fats to survive.

There are two types of fats: facilitative and functional. Facilitative fats are saturated fats enhance the taste of pet food, provide calories and energy, and help with digestion and vitamin absorption.

Facilitative fats often get a bad rap. In truth, though, they are dangerous only if they’re consumed in large amounts.

Functional fats, which are sometimes essential fatty acids (EFA), are exactly what they sound like: fats needed for healthy body function. Pets are unable to produce these fats on their own, which is where dog owners come into play.

There are two types of EFAs: omega-3 and omega-6. Your pup needs each EFA in certain amounts for healthy living.

Omega3 for Dogs

The following are omega-3 fatty acids:

  • Alpha-linolenic acid (ALA)
  • Docosahexaenoic acid (DHA)
  • Eicosapentaenoic (EPA)

Omega6 for Dogs

The following are omega-6 fatty acids:

  • Arachidonic acid (AA)
  • Dihomo-gamma-linolenic acid (DGLA)
  • Gamma linolenic acid (GLA)
  • Linolenic acid (LA)

Although omega-3 and omega-6 fatty acids play important roles in your dog’s diet, we are going to take a deeper look at omega-3s, because that’s where fish oil enters the picture.

Omega3 Fish Oil Benefits

Before we get into the cautionary tales of fish oil, it is important to recognize why the craze started to begin with.

Omega-3 fatty acids are an important part of a healthy diet, and fish oil contains a lot of omega-3s. Here are several ways in which fish oil can benefit your beloved four-legged friend.

Fight Cardiovascular Disorders

Omega-3 fatty acids can help combat cardiovascular disorders, reduce inflammation around the heart and other vital organs, and reduce muscle loss and damage.

fish oil for dogs promotes heart health

Neurological Health & Cognitive Function

Omega-3 fatty acids can also help a pup’s brain. Several studies have reported that, compared with puppies not given an omega-3 fatty acid supplement, puppies given the supplement were significantly better at learning new tricks and commands.

Inflammatory Skin Disorders

The omega-3s in fish oil reduce inflammation and can reduce itchiness and hair loss associated with skin allergies and other skin disorders.  

fish oil for dogs can help dog allergies

Kidney Disease

Omega-3s are an important factor in kidney health and function for both dogs and cats alike.

fish oil for dogs promotes kidney health


A noteworthy study of omega-3 supplementation in cats showed that those who received the fish oil supplement had greater improvements in joint function and less pain than those who didn’t receive the supplement.

fish oil for dogs promotes healthy bones

Added Benefits

Finally, omega-3s can slow the growth of yeast (thus preventing yeast infections), support proper retina and visual cortex development, control and prevent blood clotting, and reduce cancer risk.

Fish Oil Side Effects

Despite these benefits, omega-3 fish oil supplements come with some very worrisome side effects that pet owners should know about.

Premature Aging and Disease

The omega-3 fatty acids in fish oil are extremely susceptible to oxidative damage.

Here’s why is this troubling: every single time a bottle of fish oil is opened, oxygen causes the fat particles in the fish oil to break down into smaller compounds like malondialdehyde (MDA).

These compounds then create oxygen-containing molecules called free radicals. Free radicals and MDA cause premature aging and significant damage to essential proteins and other vital cellular components, ultimately leading to disease.


We can’t deny that the fats stored in fish are chock full of omega-3s. However, the fats are also loaded with toxins.

It’s incredibly sad that our oceans are becoming increasingly polluted each day.

Arsenic, cadmium, lead, and mercury are chemicals that are rapidly contaminating our oceans because of our industrial lifestyles.

These chemicals are not broken down easily and end up in a fish’s body, and, subsequently, fish oil.

Pet parents need to know about the dangers of our oceans and how these dangers are affecting us on a daily basis, regardless of whether we choose to acknowledge it.

Heavy metals directly cause nervous system dysfunction, blindness, certain cancers, liver and kidney damage (often irreversible), and even death.

We must recognize that this is our reality, then act appropriately and according to what’s best for ourselves, our pets, and our oceans.

fish oil for dogs can contain toxins

Radiation Poisoning

In 2011, a tsunami slammed into the Fukushima nuclear power plant, causing the power plant’s reactors to melt down. This led to radioactive water seeping into the Pacific ocean.

Today, the radioactive waters have reached the west coast of North America and have infected most marine life. It’s a sad fact to think about.

Pet parents must be aware of this radioactivity in the water. Therefore, you must ask for a Certificate of Analysis (COA) if you choose to supplement your dog’s diet with fish oil.

Harming the Oceans 

Have you stopped to think about just how the fish become fish oil? Through a process called by-catch, the fish are scooped up from the ocean by nets and through a by-product of fisheries.

Unfortunately, by-catch also ensnares other marine life, such as dolphins, sea turtles, and whales

Experts have estimated that approximately 300,000 whales, porpoises, and dolphins are killed each year because of fishery nets.

Menhaden fish are highly sought after for fish oil because of their high omega-3 concentrations.

The menhaden fish are crucial for the ocean. They eat algae blooms and help keep the ocean clean and full of oxygen.

However, with the rise in popularity of fish oils, approximately 150,000 metric tons of menhaden fish are removed from our oceans every year.

This is troublesome for many reasons, including that there are now dead zones developing in our waters because of the lack of oxygen.

fish oil for dogs

Krill oil

You may be wondering if krill oil is the better choice. Sadly, no. Krill is the main food source for whales.

Experts have estimated that krill populations have dropped by 80% since the mid-1970s.

How to Choose the Best Fish Oil Supplement 

If you choose to give your dog a fish oil supplement, there are several things you should do to ensure its quality.

Types of Fish Oil 

Before we begin, dog owners should first know that three types of fish oil are currently on the market.

Natural Triglyceride Oil 

Natural triglyceride oil is the most natural and easiest for the body to absorb. However, it is not purified and may contain contaminants, such as polychlorinated biphenyls (PCB).

Ethyl Ester Oil

Ethyl ester oil is concentrated and distilled, and thus has no impurities. Therefore, it is semi-natural with high levels of omega-3 fatty acids. Specifically, ethyl ester oil has two types of omega-3s: DHA and EPA

Synthetic Triglyceride Oil

Synthetic triglyceride oil is—you guessed itsynthetic. Therefore, it absorbs the least easily of the three types of fish oil on the market. We highly recommend avoiding this type of fish oil.

Certificate of Analysis 

Dog owners should always ask for a COA from the manufacturer. Any reputable company should easily be able to provide one.

The COA is a document issued by either an in-house or third-party quality assurance team. It includes the results of all of the necessary testing performed as part of quality control.

The COA will help pet parents know that they are getting the best fish oil possible.

Wild Caught Fish 

Another thing to look for is whether the fish are farm raised or wild caught. Purchase fish oil that was derived from wild caught fish.

Studies have repeatedly concluded that farm-raised fish contain hazardous levels of PCBs, dioxins, dieldrin (a pesticide), and toxaphene (an insecticide). Additionally, the quality of life and living conditions of the fish leave much to be desired.

If you choose to give your dog a fish oil supplement, we recommend using a product like veterinarygrade Wild Alaskan Salmon Oil.

You can also look for oil derived from other wild caught fish from the Pacific ocean off the coast of South America.

Avoid Ethanol 

Finally, dog owners must ensure that they are avoiding fish oil that was processed using ethanol.

Ethanol is a cheap method of processing and can cause your pup to have some very serious health issues. Luckily, there are ways to check the ethanol levels at home.

Simply pour a small amount of the fish oil into a styrofoam cup. If the oil eats through the cup in less than 30 minutes, it’s likely that it contains ethanol.

Knowledge is Power 

The best advice we feel that we can give our readers is to do your homework.

By understanding what makes one product better than the next, you can feel confident in what you are purchasing and giving to Fido.

This is also true for fish oil (and all products) that you purchase for your own use. Make sure you are buying from a reputable company and that you are getting the best product available.

Furthermore, with the rise in popularity of products considered to be allnatural, such as fish oil, you’ll find many brands and companies offering their oils at a low cost.

We want to warn our readers that, as with many things, you truly get what you pay for with fish oil. Avoid buying the cheapest product because this can likely cause Fido more harm than good.

Here’s a good rule of thumb: if it seems too good to be true, it probably is.

Fish Oil Dosage

Luckily, if you choose to add a fish oil supplement to your dog’s diet, you will likely no longer have to pry their mouth open and force them to swallow a pill.

Most companies got the memo that fish oil capsules and dogs typically don’t go together. Fish oil is now available in an easy-to-use liquid form. The oil can easily be added to your dog’s food.

The dosage of fish oil will ultimately depend on your dog’s weight and the type of fish oil. Many experts agree that instead of following the guidelines listed on the container, you should ask your vet how much fish oil is necessary for your dog’s individual health needs.

Additionally, we recommend easing your dog into the new supplement. Start off slowly. There’s no need to rush adding any new supplement, including fish oil.

Pet owners should also monitor their dogs when any new product is introduced. Knowing your dog’s “normal” is imperative for recognizing when anything changes.

Storing Fish Oil

Fish oil needs protection from heat, light, and air. If you do choose to purchase fish oil, we recommend buying a product that comes in a dark, airtight container and storing it in the fridge.

Additionally, due to its susceptibility to oxidation, fish oil can become rancid if not stored properly. If the fish oil has any sort of “off” smell, throw it away.

Better Alternative

We told you about the benefits of fish oil for dogs and that it provides necessary EFAs, like omega-3s, for Fido. In particular, fish oil provides your dog with omega 3s that help reduce inflammation and the risk of health issues.

Luckily, fish oil isn’t the only way that you can integrate these benefits into your pup’s life.


It may surprise pet owners to learn that fish aren’t naturally born with high levels of omega-3. Instead, they get it through their food source that provides them with the necessary nutrients.

That source is phytoplankton, which are the tiny bundles of algae and bacteria that help sustain the entire ocean.

Zooplankton consume the phytoplankton, then fish eat the phytoplankton by eating the zooplankton.

This is how omega-3 travels through the food chain and reaches the fish that we turn into fish oil supplements.

Here’s why phytoplankton is so great.

Phytoplankton is a whole food, meaning that your pup’s digestive tract doesn’t need to digest it first before absorbing all of its nutrients. For dogs with digestive issues, phytoplankton is a great way to get the benefits of omega-3 fatty acids.


This is a major benefit over phytoplankton from plant sources of omega-3 fats, which are much harder for your dog to digest and convert into energy. Additionally, phytoplankton can grow in controlled, filtered water farm environments.

Typically we don’t promote farm raising. However, for phytoplankton, farm raising means that the omega-3 source doesn’t contain heavy metals, radiation, or toxins and you don’t have to worry about potential negative effects on our oceans.

Finally, phytoplankton contains a powerful antioxidant known as superoxide dismutase, considered the king of all antioxidants.

As you can see, we are big fans of phytoplankton and highly encourage our readers to check it out as an alternative to fish oil supplementation.

Fish Oil for Dogs: The Bottom Line

Your dog’s health and well-being mean the world to you. We understand. Here at Honest Paws, we are all dog owners and lovers of all living creatures. That’s why we can honestly say that we know how important your pup’s happiness is to you.

The internet can be a remarkable thing. We have so much information right at our fingertips. As always, we recommend that our readers do their research.

Before hopping on the latest trend, know the pros and cons (if any). A supplement like fish oil may have been something we believed we needed a handful of years ago.

However, now, mounting evidence suggests that we may be better off without it. Furthermore, a supplement like CBD benefits pets in several different ways. Again, a simple Google search can truly shed light on so much.

Finally, we aren’t trying to scare our readers into throwing out their fish oil supplements. However, it is critical to know as much as you can about the product.

Where does it come from? Were the fish farm raised or wild caught? What about the absorbability?

Doing your homework and researching every new product is a simple way to ensure that you are doing the very best for Fido. Isn’t that what we all ultimately want?


About the author

JoAnna Pendergrass

JoAnna Pendergrass, DVM is a veterinarian and freelance medical writer in Atlanta, GA. After earning her Doctor of Veterinary Medicine degree from the Virginia-Maryland College of Veterinary Medicine, she pursued a non-traditional career path as a veterinarian. JoAnna completed a 2-year postdoctoral research fellowship in neuroscience at Emory University’s Yerkes National Primate Research Center, then became a medical writer. As founder and owner of JPen Communications, a medical communications company, JoAnna is passionate about educating pet parents about pet care and responsible pet ownership. Although she does not currently have any pets to call her own, she loves living vicariously through other pet parents and watching Nat Geo!

  • John says:

    Thanks for wonderful information. …

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