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Flaxseed oil vs. fish oil: understanding the differences

Medically reviewed on September 9, 2022 by Jillian Foglesong Stabile, MD, FAAFP. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.


Table of contents


Flaxseed oil and fish oil are necessary sources of nutrients for the human body. They both provide the body with essential nutrients known as omega-3 fatty acids and an array of other crucial vitamins and minerals that may help support heart health. [1] Essential nutrients are not produced by the body and must be obtained through diet or nutritional supplements. [2]

But what are the differences when it comes to flaxseed oil vs. fish oil? Flaxseed oil may more effectively support gastrointestinal health [3], while fish oil may promote skin and heart health and brain development. [4] That said, each omega-3 powerhouse can be further differentiated by its makeup, uses, and additional potential benefits.

What is flaxseed oil?

Flaxseed oil, also known as linseed oil, is derived from the seeds of the flax plant. The growth and cultivation of the flax plant date back to at least the Stone Age, when the seeds were used as a food source, and the plant’s fibers were used to make textiles. [5]

Today, the flax plant remains an important agricultural product. [6] We still use its fibers for industrial purposes, like making yarn and fabrics.

Flaxseed Oil Benefits

Flaxseeds are still put to a wide range of dietary uses, topping salads, adding an Omega-3-packed boost to baked goods, or supplementing your midday as a toasted snack.

The seeds of the flax plant are packed with many nutrients, including:

  • Calcium
  • Copper
  • Fiber
  • Iron
  • Magnesium
  • Manganese
  • Phosphorous
  • Protein
  • Thiamin

To make flaxseed oil, fresh flax seeds are dried and cold-pressed to retain the seeds’ antioxidant properties. [2] Additionally, they’re rich in omega-3 fatty acids, making them a popular health supplement.

More specifically, flaxseeds contain an omega-3 fatty acid known as alpha linolenic acid (ALA). [7] ALA is a plant-based fatty acid that’s an essential component of a healthy diet. As a fatty acid, it may help support heart health and aid brain development and function.

There’s also evidence that ALA and other fatty acids can support healthy blood pressure levels. However, further studies are required before this link can be definitively confirmed. [8]

Flaxseed oil is also used in various industrial products, from paints and printing inks to varnish and linoleum. [6]

What is fish oil?

Fish oil comes from certain fish known as “oily fish.” Oily fish are distinguished from other kinds of fish because they store their oil, in the form of fat, in their soft tissue, whereas other types of fish store oil in their livers. [9]

Oily fish include a variety of fatty fish species, such as:

  • Anchovies
  • Herring
  • Mackerel
  • Salmon
  • Sardines
  • Trout

Certain shellfish also contain fish oil, like crabs, mussels, and oysters.

Fish Oil Benefits

Like flaxseed oil, fish oil is rich in omega-3 fatty acids. Unlike flaxseed oil, fish oil doesn’t contain ALA, which is only found in plants. Instead, fish oil is rich in two other kinds of animal-based fatty acids: [10]

  • Eicosapentaenoic acid (EPA)
  • Docosahexaenoic acid (DHA)

EPA and DHA may contribute to the potential benefits of fish oil. Like ALA, they are essential nutrients that the human body needs to perform functions that range from the simplest, like moving muscles, to the most vital, like growing new cells. [10] Because these nutrients do not occur naturally in the human body, we can only get them through dietary sources.

Both EPA and DHA are notable for their anti-inflammatory properties as omega-3 fatty acids, such as mediating the inhibition of proinflammatory molecules and the increased production of inflammation-resolving molecules. [11]

Inflammation typically occurs when your body perceives a threat from injury or infection. In response to the threat, your body sends inflammatory cells to the relevant area to kill bacteria and viruses or begin the healing process. [12]

In other words, inflammation is a good thing. But it can cause a few unpleasant side effects, such as:

  • Swelling
  • Tenderness
  • Pain

In some cases, your body might produce inflammatory cells even when it doesn’t need them, which can result in various chronic inflammatory conditions. [12]

Anti-inflammation may be the most well-known benefit of EPA and DHA, but it isn’t the only one. Additional potential health benefits associated with these fatty acids include:

  • Heart health support [10]
  • Mood support [13]
  • Skin health support [14]
  • Joint pain support [15]

Some studies have also linked fatty acids with liver and bone health. According to a 2016 review of several clinical studies, omega-3 supplementation was beneficial in lowering the fat content in the livers of people with nonalcoholic fatty liver disease, potentially through omega-3 fatty acid’s role as a negative regulator of liver fat generation. [16] Another 2020 study suggests that fatty acids may play a role in preventing bone decay. [17]

Additionally, esterified fish oil, which removes artificially induced alcohol to create a more natural product, is better tolerated by the gastrointestinal system and may be absorbed by the body more easily. [18]

Flaxseed oil vs. fish oil: 3 differences

So, when it comes to flaxseed oil vs fish oil, what are the differences? They both contain omega-3 fatty acids and tout numerous potential health benefits. But is one more effective or beneficial than the other?

Although flaxseed oil and fish oil present many similar benefits, they have three distinct differences.

They contain different omega-3 fatty acids

Fish oil contains two fatty acids, EPA and DHA, while flaxseed oil only has ALA. Although the human body needs all three to function properly, it doesn’t use them in the same ways.

When EPA and DHA enter the body, they’re immediately used as omega-3 fatty acids. They are distributed to cell membranes throughout the body, with cell tissue in the brain, retina, and myocardium receiving slightly greater amounts. [19]

On the other hand, the human body must convert ALA into EPA or DHA before using it. Unfortunately, making that conversion isn’t something the body does very effectively. Only 10% to 15% of the ALA a person consumes provides the benefits of omega-3 fatty acids. [7] The remainder is metabolized into energy.

Their potential uses differ

Although flaxseed oil and fish oil have overlapping potential health benefits, there are some differences.

Some of these differences go back to the specific types of omega-3 fatty acids that each oil contains. As mentioned, the human body isn’t as good at converting ALA from flaxseed oil into EPA or DHA. This automatically limits the extent to which flaxseed omega-3s can work within the body.

That said, flaxseed oil and fish oil may serve different purposes throughout the body:

  • Flaxseed oil – Flaxseed oil may benefit your gastrointestinal system, which fish oil can’t match. A 2015 study found that flaxseed oil was effective as both a laxative and an anti-diarrheal in mice. [3] According to another study, it also promoted bowel consistency in people with certain kidney diseases. [20]
  • Fish oil – In addition to its possible connection to heart and skin health, studies suggest that fish oil may play a role in brain growth and development, especially in fetuses. [4] Fish oil is also believed to contribute to ocular health in infants and may help increase their resilience against allergies. [21]

Flaxseed doesn’t contain mercury

One common concern that many people have when it comes to taking fish oil supplements or even upping their omega-3 intake with seafood is the level of mercury that many fish contain. Of particular concern is methyl mercury, which some fish absorb from eating other water life. [22]

Methyl mercury can have a negative impact on the human body, particularly about its ability to disrupt:

  • The central nervous system
  • The cardiovascular system

The Centers for Disease Control and Prevention recommends that people who breastfeed, infants, and young children limit their consumption of mercury-dense fish or fish products. [23]

Consequently, flaxseed oil supplementation is often the choice for those looking to supplement their diet with omega-3 fatty acids without the potential risk of mercury. It’s also a recommended substitute for people with fish or shellfish allergies. That said, keep in mind that flaxseed oil does not provide as many omega-3 fatty acids as fish oil. [7]

Supplement your diet with Everlywell

Although flaxseed oil and fish oil are both vital components of a well-rounded diet, fish oil can provide more health benefits than flaxseed oil due to its high omega-3 composition. To support your heart, skin, and brain health, look for an oil supplement with esterified omega-3 fish oil.

The Everlywell Omega-3 Fish Oil supplement contains esterified omega-3 fish oil in addition to vitamin E. It may support heart, brain, and skin health, infant brain development, and sperm motility for those trying to conceive.

Give your body the nutrients it needs to flourish with Everlywell.

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References

  1. Ramel A, Martinez JA, Kiely M, Bandarra NM, Thorsdottir I. Moderate consumption of fatty fish reduces diastolic blood pressure in overweight and obese European young adults during energy restriction. Nutrition. 2010;26(2):168-174.
  2. The Benefits of Flaxseed Oil. Cleveland Clinic. URL. Accessed September 9, 2022.
  3. Hanif Palla A, Gilani AH. Dual effectiveness of Flaxseed in constipation and diarrhea: Possible mechanism. J Ethnopharmacol. 2015;169:60-68.
  4. Simopoulos AP. Omega-3 fatty acids in health and disease and in growth and development. Am J Clin Nutr. 1991;54(3):438-463.
  5. Flax. Purdue.edu. URL. Accessed September 9, 2022.
  6. Flax. Britannica. URL. Accessed September 9, 2022.
  7. Why not flaxseed oil? Harvard Health. URL. Accessed September 9, 2022.
  8. Alpha-linolenic acid. Mount Sinai. URL. Accessed September 9, 2022.
  9. Fish and shellfish. National Health Service. URL. Accessed September 9, 2022.
  10. Fish oil. Mayo Clinic. URL. Accessed September 9, 2022.
  11. Omega-3 Fatty Acids. StatPearls. URL. Accessed September 9, 2022.
  12. Inflammation: What Is It, Causes, Symptoms & Treatments. Cleveland Clinic. URL. Accessed September 9, 2022.
  13. Amminger GP, Schäfer MR, Papageorgiou K, et al. Long-chain omega-3 fatty acids for indicated prevention of psychotic disorders: a randomized, placebo-controlled trial. Arch Gen Psychiatry. 2010;67(2):146-154.
  14. Balić A, Vlašić D, Žužul K, Marinović B, Bukvić Mokos Z. Omega-3 Versus Omega-6 Polyunsaturated Fatty Acids in the Prevention and Treatment of Inflammatory Skin Diseases. Int J Mol Sci. 2020 Jan 23;21(3):741.
  15. Kuszewski JC, Wong RHX, Howe PRC. Fish oil supplementation reduces osteoarthritis-specific pain in older adults with overweight/obesity. Rheumatol Adv Pract. 2020 Jul 23;4(2):rkaa036.
  16. Lu W, Li S, Li J, Wang J, Zhang R, Zhou Y, Yin Q, Zheng Y, Wang F, Xia Y, Chen K, Liu T, Lu J, Zhou Y, Guo C. Effects of Omega-3 Fatty Acid in Nonalcoholic Fatty Liver Disease: A Meta-Analysis. Gastroenterol Res Pract. 2016;2016:1459790.
  17. Sharma T, Mandal CC. Omega-3 fatty acids in pathological calcification and bone health. J Food Biochem. 2020;44(8):e13333.
  18. Dyerberg J, Madsen P, Møller JM, Aardestrup I, Schmidt EB. Bioavailability of marine n-3 fatty acid formulations. Prostaglandins Leukot Essent Fatty Acids. 2010;83(3):137-141.
  19. Surette ME. The science behind dietary omega-3 fatty acids. CMAJ. 2008 Jan 15;178(2):177-80.
  20. Ramos CI, Andrade de Lima AF, Grilli DG, Cuppari L. The short-term effects of olive oil and flaxseed oil for the treatment of constipation in hemodialysis patients. J Ren Nutr. 2015;25(1):50-56.
  21. Shulkin M, Pimpin L, Bellinger D, et al. n-3 Fatty Acid Supplementation in Mothers, Preterm Infants, and Term Infants and Childhood Psychomotor and Visual Development: A Systematic Review and Meta-Analysis. J Nutr. 2018;148(3):409-418.
  22. Risks of Mercury in Fish. Washington State University. URL. Accessed September 9, 2022.
  23. Mercury. Centers for Disease Control and Prevention. URL. Accessed September 9, 2022.
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