Flax flexes its nutritional value in human foods, particularly in supplements, bakery items and plant-based products, where it provides fiber and omega-3 fatty acids. Like many other popular human nutraceuticals, flax can be a functional ingredient in companion animal products too. Flax, also known as linseed, appears in many forms in dog and cat food: oil, whole seed, ground seed, mucilage and press cake. Numerous peer-reviewed studies in dogs and cats have examined flax as a source of alpha-linolenic acid and dietary fiber, and as a plant-based pet food ingredient. This research provides a strong base for pet food marketers and formulators when using flax.
Dogs
Flaxseed oil as a source of omega-3 fatty acids
A controlled feeding study published in the British Journal of Nutrition evaluated breed-related differences in omega-3 fatty-acid metabolism in dogs fed flaxseed oil (Purushothaman et al., 2011). In the study, flaxseed oil increased plasma alpha-linolenic acid and eicosapentaenoic acid concentrations in dogs over the study period.
More recently, a 16-week trial published in Frontiers in Veterinary Science compared camelina (or false flax), flaxseed and canola oils in healthy adult dogs (Richards et al., 2023). According to those research results, flax compared favorably with other seed oils. There were no significant differences among oil treatments for the measured skin and coat parameters or circulating inflammatory and oxidative markers in healthy dogs under the study conditions.
Formulation implications:
- Flaxseed oil may be an effective way to increase circulating alpha-linolenic acid in dogs.
- When positioning products around skin and coat support, formulators should note that in healthy dogs, flaxseed oil performed comparably to other plant oils in the measured outcomes.
- Oxidative stability and total dietary fat balance remain important considerations due to the high degree of unsaturation in flaxseed oil.
Whole flaxseed, mucilage and press cake in canine diets
Flax contributes more than oil. A crossover study published in the International Journal of Obesity evaluated flaxseed mucilage in dogs and reported reduced apparent fat digestibility, particularly when combined with dietary calcium (Nybroe et al., 2016). Fecal characteristics were also affected, suggesting that inclusion level influences tolerance.
A more recent study in Animals evaluated oilseed press cakes, including linseed press cake, as plant-based protein sources in adult dog diets (Godglück et al., 2025). The linseed-based diet showed lower apparent crude protein digestibility than comparator oilseed cakes and differences in fecal characteristics.
Formulation implications:
- Ground flaxseed and flax-derived fiber ingredients can contribute dietary fiber but may influence fat digestibility and stool quality at higher inclusion levels.
- Linseed press cake may be used in plant-forward formulations, but digestibility should be validated in finished-product testing.
- Ingredient form matters: ground seed may improve nutrient availability compared to whole seed.
Cats
Ground flaxseed and flaxseed oil as alpha-linolenic acid sources
A study published in Animals evaluated ground flaxseed in healthy adult cats (Panasevich et al., 2022). Dietary ground flaxseed increased serum alpha-linolenic acid concentrations within 14 days and did not negatively affect nutrient digestibility or stool quality.
An earlier study in Veterinary Immunology and Immunopathology compared fish oil and flaxseed oil in cats (Park et al., 2011). In this study, flaxseed oil increased circulating alpha-linolenic acid, while fish oil increased eicosapentaenoic acid and docosahexaenoic acid. Both oil sources were associated with decreased histamine-induced skin responses under the study conditions, and flaxseed oil was less immunosuppressive than fish oil in certain immune measures reported.
Formulation implications:
- Flax ingredients may reliably increase alpha-linolenic acid in cats.
- Marine oils remain the direct source of longer-chain omega-3 fatty acids such as eicosapentaenoic acid and docosahexaenoic acid.
- Palatability and digestibility should be verified at the finished-product level.
Across species, the peer-reviewed literature supports flax and its derivatives as:
- A source of alpha-linolenic acid in dogs and cats.
- A plant-based ingredient aligned with sustainability and alternative protein positioning.
- A contributor of dietary fiber when used as whole seed, ground seed or mucilage.
At the same time, studies indicate that inclusion level and ingredient form can affect digestibility and fecal characteristics.
For marketers, flax offers a recognizable, plant-based ingredient with documented effects on circulating omega-3 fatty-acid status. The science supports positioning around omega-3 content and general skin and coat support, but not therapeutic or disease-treatment claims.
Sources
Godglück, C., et al. (2025). Investigation of the Digestibility, Fecal Characteristics, and Palatability of Oil Mil By-Products as a Plant-Based Protein Source in Canine Diets. Animals, 15.
Nybroe, S., Astrup, A., & Bjørnvad, C. R. (2016). Dietary supplementation with flaxseed mucilage alone or in combination with calcium in dogs: Effects on apparent digestibility of fat and energy and fecal characteristics. International Journal of Obesity, 40(9), 1446–1452.
Panasevich, M. R., Kerr, K. R., Dilger, R. N., Fahey, G. C., & Swanson, K. S. (2022). Dietary ground flaxseed increases serum alpha-linolenic acid concentrations in adult cats. Animals, 12.
Park, H. J., et al. (2011).Dietary fish oil and flaxseed oil suppress inflammation and immunity in cats. Veterinary Immunology and Immunopathology, 144(3–4), 349–354.
Purushothaman, S., Xu, Q., Lu, J., & Tremblay, A. J. (2011). Evaluation of breed effects on n-3 polyunsaturated fatty acid metabolism with dietary flaxseed oil supplementation in dogs. British Journal of Nutrition, 106(S1), S171–S174.
Richards, T. L., et al. (2023). Effects of dietary camelina, flaxseed and canola oil supplementation on skin and coat health, inflammation and oxidative markers in dogs. Frontiers in Veterinary Science, 10.
