Fish Oil

Research Library

This scientific research is for informational use only. The results reported may not necessarily occur in all individuals. Care/of provides this information as a service. This information should not be read to recommend or endorse any specific products.

Omega-3 fatty acids are essential for health and can only be obtained through diet. The most common forms of omega-3’s are EPA, DHA and ALA. Dietary sources of omega-3’s include fatty fish, walnuts, flaxseeds, and canola. Fatty fish like salmon, mackerel, herring, lake trout, sardines and albacore tuna are highest in omega-3 fatty acids.The American Heart Association recommends people eat two servings of fatty fish per week due to its beneficial omega-3 fatty acids, yet most Americans don’t get enough omega-3’s. Research has shown that omega-3’s benefit multiple body systems and play a role in maintaining a healthy cardiovascular system.


Fish oil has shown initial promising results as an ingredient for joint health. A 12 month, double-blind, placebo-controlled study found that patients taking 2,600mg of omega-3 per day experienced less joint pain than those taking a placebo. Patients also reported less use of concomitant antirheumatic medications during the period of fish oil supplementation.

An in-vitro study in 2000 examined the molecular mechanisms by which omega-3s can affect inflammatory markers in cartilage. The study found that omega-3 fatty acids create a reduction in the expression and activity of aggrecanases, proteoglycan-degrading enzymes, the expression of inflammation-inducible cytokines interleukin (IL)-1alpha and tumor necrosis factor (TNF)-alpha, and cyclooxygenase (COX-2), but not the constitutively expressed cyclooxygenase COX-1.

  1. Long-term effect of omega-3 fatty acid supplementation in active rheumatoid arthritis. A 12-month, double-blind, controlled study.

    Geusens P, Wouters C, Nijs J, Jiang Y, Dequeker J., Arthritis and Rheumatism, 1994

  2. n-3 fatty acids specifically modulate catabolic factors involved in articular cartilage degradation.

    Curtis CL, Hughes CE, Flannery CR, Little CB, Harwood JL, Caterson B., The Journal of Biological Chemistry, 2000

Important when not eating enough fish

The American Heart Association recommends that adults eat two servings of fish per week for beneficial omega-3’s. Individuals who do not eat fish, or don't often eat fish, would benefit from supplementation (1, 2).

  1. Fish and Omega-3 Fatty Acids

    American Heart Association®, American Heart Association®, 2015

  2. Omega-3 Content of Frequently Consumed Seafood Products

    Seafood Health Facts, Seafood Health Facts (website), 2016

Helps maintain cognitive health

Fatty fish is one of the best sources of omega-3 fatty acids, which are a major building block of the brain. Omega-3s play a role in sharpening memory and improving mood, as well as supporting cognitive performance.

Research suggests that DHA improves facets of memory and cognition and that greater consumption of omega-3 rich fish leads to better performance on cognitive battery tests (1).

In elderly adults, omega-3 intake has been associated with a slower rate of cognitive decline. Individuals who consumed two or more servings of fish per week were found to have 13% slower cognitive decline (2). Another study found that higher plasma levels of EPA in adults age 65 or older was associated with lower gray matter atrophy of the right hippocampal/parahippocampal area and of the right amygdala (3).

Research has indicated there may be a link between DHA levels and cognitive health and function. One study found participants in the lowest quartile of red blood cell DHA levels had smaller brain volume and greater white matter hyperintensity volume. Participants with lower DHA also had lower scores on tests of visual memory, executive function and abstract thinking models (4).

Similar results were found in another study of serum phospholipid levels. Higher DHA levels were associated with better performance on tests of nonverbal reasoning, and improved mental flexibility, working memory, and vocabulary on neuropsychological tests. EPA and ALA levels did not show any effect on cognitive performance (5).

  1. Dietary intake of fatty acids and fish in relation to cognitive performance at middle age

    Kalmijn S, van Boxtel MP, Ocké M, Verschuren WM, Kromhout D, Launer LJ., Neurology, 2004

  2. Plasma long-chain omega-3 fatty acids and atrophy of the medial temporal lobe.

    Samieri C, Maillard P, Crivello F, Proust-Lima C, Peuchant E, Helmer C, Amieva H, Allard M, Dartigues JF, Cunnane SC, Mazoyer BM, Barberger-Gateau P., Neurology, 2012

  3. Red blood cell ω-3 fatty acid levels and markers of accelerated brain aging.

    Tan ZS, Harris WS, Beiser AS, Au R, Himali JJ, Debette S, Pikula A, Decarli C, Wolf PA, Vasan RS, Robins SJ, Seshadri S., Neurology, 2012

  4. Serum phospholipid docosahexaenonic acid is associated with cognitive functioning during middle adulthood.

    Muldoon MF, Ryan CM, Sheu L, Yao JK, Conklin SM, Manuck SB., The journal of nutrition, 2010

  5. The effects of omega-3 fatty acids monotherapy in Alzheimer's disease and mild cognitive impairment: a preliminary randomized double-blind placebo-controlled study.

    Chiu CC, Su KP, Cheng TC, Liu HC, Chang CJ, Dewey ME, Stewart R, Huang SY., Progress in neuro-psychopharmacology and biological psychiatry, 2008

Supports eye health

DHA is a key component of all cell membranes and is found in abundance in the brain and eye (1). Very high levels of DHA are present in the retina, specifically in the disk membranes of the outer segments of photoreceptor cells (2).

In a randomized, double blind clinical trial sixty-four patients with dry eye symptoms between the ages of 45 and 90 years were randomized into 2 groups: 33 persons in the treatment group and 31 persons in the placebo group. The treatment group received 2 capsules of omega-3 fish oil (each containing 180 mg EPA and 120mg DHA) daily for 30 days, and the placebo group received 2 medium chain triglyceride oil capsules daily for 1 month. The study found that oral consumption of omega-3 fatty acids (180mg EPA and 120mg DHA twice daily for 30 days) is associated with a decrease in the rate of tear evaporation, an improvement in dry eye symptoms, and an increase in tear secretion (3).

The European Food Safety Authority concluded that a cause and effect relationship has been established between the consumption of DHA and the maintenance of normal vision (4).

  1. Omega-3 fatty acids EPA and DHA: Health Benefits throughout life

    Swanson, D. Block R. Mousa S., Adv Nutr., 2012

  2. Effects of Omega-3 Fatty Acids on Eye Health: Summary

    Hodge W, Barnes D, Schachter HM, et al, AHRQ Evidence Report Summaries. Rockville (MD): Agency for Healthcare Research and Quality (US); 1998-2005. 117., 2005

  3. A randomized controlled trial of omega-3 fatty acids in dry eye syndrome

    Bhargava R, Kumar P, Kumar M, Mehra N and Mishra A, International journal of ophthalmology, 2013

  4. Towards establishing dietary reference intakes for eicosapentaenoic and docosahexaenoic acids

    Harris, WS, Mozaffarian D., Lefevre M., Toner CD., Colombo J., Cunnane SC., Holden JM., Klurfeld DM., Morris MC., and Whelan J., J. Nutr. 139: 804S – 819S, 2009


Omega-3 from fish oil has been extensively researched for its benefits on the heart, with studies performed to assess its effects on cardiovascular disease, cholesterol and hypertension. In fact, the American Heart Association recommends eating fish, particularly fatty fish, at least two times per week. Fatty fish like salmon, mackerel, herring, lake trout, sardines and albacore tuna are high in omega-3 fatty acids. For more information about the research on omega-3 fatty acids for heart health, please see the links below:

  1. Omega-3 fatty acids for cardioprotection.

    Lee JH, O'Keefe JH, Lavie CJ, Marchioli R, Harris WS., Mayo clinic proceedings, 2008

  2. Fish and Omega-3 Fatty Acids

    American Heart Association®, American Heart Association®, 2015

  3. Omega-3 Fatty Acids

    Office of Dietary Supplements, National Institutes of Health, 2016