By Dial A Vet Veterinary Team
Linseed, as flaxseed is usually called in Australian shops, turns up in dog food ingredient lists, in "skin and coat" supplements and in the breakfast mix on your bench. It is safe for most dogs in small amounts. The common claim that it does the same job as fish oil is where things get muddled, and it is worth understanding why before you start adding it to your dog's bowl.
Key takeaways
- Plain flaxseed (linseed) is not toxic to dogs and is used in some commercial dog foods.
- Whole seeds often pass straight through. Ground seed or meal is better absorbed.
- Flax contains ALA, a plant omega-3. Dogs convert only a small share of it into the EPA and DHA found in fish oil.
- If your vet recommends omega-3s for skin, joints or kidneys, they will usually mean a marine source and a specific product.
- Hardware-store linseed oil is not food and should be kept well away from dogs.
- Related: chia seeds, flaxseed for cats, vomiting and diarrhoea in dogs.
What is in a flaxseed
Flaxseed is rich in fat (around 40 percent by weight), much of it alpha-linolenic acid (ALA). It also has soluble fibre that turns gel-like in water, some protein, and plant compounds called lignans. Golden and brown linseed are nutritionally similar.
A complete and balanced dog food already supplies the essential fatty acids your dog needs, so flax is an optional extra rather than a requirement.
The omega-3 question
Many of the benefits people associate with omega-3s in dogs, such as support for itchy skin or arthritic joints, come from studies of EPA and DHA, the long-chain omega-3s in fish and some algae oils. Dogs can convert some ALA from flax into EPA, but the conversion is limited and DHA production is minimal. That means a spoonful of linseed meal does not deliver what a vet-recommended fish oil does.
Flax is not useless. It adds fibre and some fatty acids. It just should not be relied on to manage a medical condition. If your dog has skin, joint or kidney issues, ask your vet whether a specific omega-3 product makes sense and how much to use.
Whole, ground or oil
- Whole seeds are hard and slippery. Many pass through undigested, so your dog gets little from them.
- Ground seed or meal is better used. Grind small batches and keep them in a sealed jar in the fridge, because ground flax goes rancid within a couple of weeks. Rancid flax smells bitter or fishy.
- Food-grade flaxseed oil is sold in the fridge section of health food shops. It adds calories quickly and can loosen stools.
Raw flaxseed naturally contains small amounts of cyanogenic compounds. These are not a concern at the sprinkle-sized amounts used in food, but they are another reason not to feed large quantities.
How much is reasonable
For a medium-sized dog, a light sprinkle of ground linseed over a meal a few times a week is plenty. Small dogs need less. Start with a tiny amount and build up over a week, since the fibre can cause wind or loose stools at first. Give plenty of fresh water. Treats and extras of all kinds are best kept to a small share of your dog's daily food.
Hardware linseed oil is a different product
Boiled linseed oil from the hardware store, used to treat timber and cricket bats, is not food. It often contains metal drying agents and solvents. Dogs who lick or chew it may drool, vomit or have diarrhoea, and larger exposures can be more serious. Rags soaked in it can also self-heat and catch fire if bundled up, so dispose of them carefully. If your dog gets into it, call your vet or the Animal Poisons Helpline on 1300 869 738.
Dogs who should skip flax
- Dogs with a history of pancreatitis or on a low-fat diet
- Dogs on prescription diets, unless your vet agrees
- Dogs with a sensitive gut that reacts to new fibre
- Dogs scheduled for surgery, until you have checked with your vet about any supplements
What to do if your dog ate a lot of flax
A dog who eats a bag of linseed may have bloating, wind, loose stools or vomiting. Dry seeds absorb water, so offer fresh water and watch closely. Call your vet if your dog vomits repeatedly, has a swollen or painful belly, strains without passing stool, or seems unwell. Do not try to make your dog vomit at home.
When it is an emergency
Seek urgent care if your dog has a tight, swollen belly, is retching without producing anything, is restless and uncomfortable, collapses, or has licked or swallowed hardware linseed oil and is unwell.
FAQ
Will flaxseed make my dog's coat shiny?
Some owners notice a change, but evidence in dogs is limited. Coat problems often have medical causes worth checking with your vet.
Is flaxseed safe for puppies?
Puppies do best on their growth diet without extras. Ask your vet before adding anything.
Can flax replace fish oil for my dog's arthritis?
Not reliably. Plant omega-3 converts poorly to the forms studied for joint support. Talk to your vet about options.
Talk with a vet
Not sure whether a supplement is worth it for your dog? A Dial A Vet veterinarian can review your dog's diet and health and help you decide. Book a Dial A Vet consult.
References
- Bauer JE. Therapeutic use of fish oils in companion animals. Journal of the American Veterinary Medical Association. 2011;239(11):1441-1451.
- Merck Veterinary Manual. Nutritional requirements of small animals.
- National Research Council. Nutrient Requirements of Dogs and Cats. Washington DC: National Academies Press; 2006.
- WSAVA Global Nutrition Committee. Global nutrition guidelines and selecting the best food for your pet.
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If you are worried about your pet right now, contact your local vet or nearest emergency animal hospital.