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Fish Oil Supplements: Are the Fish Oil Benefits True?

Written by Dr. Group, DC Founder
A cup full of fish oil supplements.

The golden, egg-shaped capsules are the latest craze among health seekers. Found in the tissues of oily, cold-water fish, the oil contains omega-3 fatty acids, which are essential for many vital functions in the body, including brain function, muscle activity, and normal growth and development. But are fish oil capsules the only — or the best — source of omega-3 fatty acids?

What Is Fish Oil?

Fish oil comes from fatty fish, mostly sardines, anchovies, and mackerel. After being caught in nets, the raw fish are shipped to a factory where they get ground up and steam-cooked. A centrifuge separates the meat from the oil. Impurities get removed from the oil, and then antioxidants are added to the fish oil — it is not typically just pure fish oil.

Below are some of the traditional sources of fish oil.

  • Sardines
  • Mackerel
  • Herring
  • Anchovies
  • Black cod
  • Salmon

Why Do People Take Fish Oil?

People take fish oil because it contains omega-3 fatty acids, which science suggests provide a host of health benefits. Fish oil contains at least three different fatty acids, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and alpha-linolenic acid (ALA) — but mainly DHA and EPA.

Various fish oil products contain different ratios of DHA to EPA, and scientists are only beginning to tease apart the specific role they play in providing the health benefits — ranging from eye health to mental wellness to immune system and cardiovascular support.

Let’s take a closer look at health claims about the benefits of fish oil. Recent studies indicate that DHA plays a stronger role in providing the scientifically touted benefits, and alternatives like microalgae oil may have more favorable ratios of DHA to EPA — in other words, more DHA and less EPA[1].

Is Fish Oil Bad For You?

Although fish oil contains high amounts of the omega-3 fatty acids that scientists tout the benefits of, there are several concerns raised from their use. A plant-based diet will help your health in many ways, including helping to prevent diabetes to balancing cholesterol and blood sugar — and fish oil does not fit into a plant-based or vegan diet. Marine-harvested fish is often laced with mercury and other contaminants. In fact, some studies have even linked fish oil consumption to higher rates of prostate cancer.[1, 3]

In July 2018, National Public Radio (NPR) ran a radio piece on the dangers of fish oil to both human health and the ocean.[2] Although omega-3 fatty acids undeniably play an important role in the human body, Paul Greenberg — author of Seafood and the Quest for a Long Life and a Healthier Planet — convincingly argued that not only is the craze for fish oil supplements depleting our planet’s marine ecosystems, they are leading people to have unnaturally high mercury levels in their bodies.

When Greenberg went on a fish diet for a year, it raised his mercury level, as tested in a hair sample, to 5 ppm (parts per million) — people at this level experience detectable changes in how people perform basic tasks involving fine motor skills and memory.[2]

What Are the Alternatives?

In most cases, the type of omega-3 fatty acid available in plant-based sources is alpha-linolenic acid (ALA), which the body can convert to the DHA and EPA. Most plant-based sources may not yield as high a concentration of DHA and EPA as marine sources, but one exception in the plant world is algae, which does contain high amounts of bioavailable DHA and EPA.

Besides algae oil, you can also buy flaxseed oil as a plant-based alternative supplement. You can also get omega-3 fatty acids by eating flax seeds, sesame seeds, and hemp seeds or adding them to your salads, smoothies, or recipes. Here’s a list of plant-based options with high levels of omega-3 fatty acids:

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Top Fish Oil (Omega 3) Benefits

Essential to heart and brain health, DHA and EPA provide the main benefits associated with fish oil. Omega-3 fatty acids like DHA and EPA play a role in everyday health and wellness, particularly when combined with maintaining a healthy body weight and regular exercise. Here are the top benefits that you can get from omega-3 fatty acids.

Beautifies Skin and Hair

DHA and EPA help support healthy skin and hair. Deficiencies of these fatty acids in the diet can lead to dry, irritated skin, and dandruff, while their presence helps maintain skin moisture and support hair growth. Some small studies link increased consumption with a reduction in the symptoms of eczema, perhaps due to its anti-inflammatory properties.[4]

Supports Heart Health

Whether in food or supplements, consuming fish oil and omega-3s may support cardiovascular health. One review of the scientific literature found that increased fish oil consumption reduces the rate of adverse cardiac outcomes such as heart attack and stroke.[5, 6] Some studies suggest fish oil promotes normal blood pressure, especially in people with moderate to severe hypertension.[7] Omega-3s can also reduce high levels of triglycerides, another risk factor for heart disease.[8] Omega-3s may also reduce the risk of a blood clot, reduce total cholesterol, and normalize high-density lipoprotein (HDL) or "good" cholesterol.[9]

Bolsters Brain Health

The relationship between the omega-3 fatty acids and brain health is an intriguing subject for researchers — especially when you consider that somewhere between 5 to 10 percent of the mass of the human brain is made up of DHA.

DHA is necessary for optimal brain health and cognitive function at all stages of life, from infants and children to adults and the elderly. DHA plays a key role in neural signaling and helps our brains work faster. A deficiency of DHA in the body has been associated with deficits in learning and cognitive function.

Scientific interest in fish oil and omega-3s for brain health revolves around conditions such as Alzheimer's disease and attention-deficit/hyperactivity disorder (ADHD), as well as depression and other mental health conditions. One review of the literature found that omega-3 fatty acids help discourage mood and anxiety disorders.[10]

Soothes Inflammation

DHA and EPA have natural anti-inflammatory properties. In normal healing, inflammation — redness, swelling, and irritation — is the body's reaction to infection and a necessary part of the immune system. However, when inflammation does not subside, or when it exists without the presence of an infection, it can have detrimental effects on the body in many ways. The ability of omega-3 fatty acids to reduce inflammation means that fish oil may help with the symptoms of various autoimmune disorders — including rheumatoid arthritis, inflammatory bowel disease, asthma, and allergies.[11]

Strengthens the Immune System

Omega-3 fatty acids may have benefits for people with compromised immune systems. A 2013 study found that DHA-rich oil enhances the activity of B cells, which are white blood cells that help make antibodies for a healthy immune response.[12]

Supports Eye Health

Some studies show that DHA and EPA may help to relieve the symptoms of dry eye, a condition in which the eye cannot maintain its protective coating of tears. The omega-3 fatty acids in fish oil may improve the function of the glands in the eyes that produce tears, thereby helping to reduce irritation from dry eye.[13] Scientific evidence is mixed concerning the benefits for age-related macular degeneration, which involves the deterioration of the central portion of the retina and is the leading cause of vision loss in the U.S. While some studies support the use of high-dose fish oil for macular degeneration, other studies find that fish oil supplements do not alter the progression of the disease.[14]

May Aid in Cancer Prevention

Omega-3 fatty acids may protect from certain cancers, such as breast and colorectal cancer. Researchers have found that these oils can reduce cancer-causing compounds, such as prostaglandin E2 in the colon, which may trigger cancer. And various studies associate increased consumption of marine omega-3 fats with a reduced risk of breast cancer.[15]

Some studies, however, link high-dose fish oil consumption with an increased risk of prostate cancer.[16] Authors involved in these studies caution men against taking "megadoses" of fish oil supplements for this reason.

Which Is Best: Food or Supplement?

Our bodies evolved to eat whole food rather than the isolated compounds and nutrients found in supplements. But because most fatty fish contains high levels of mercury, relying on whole fish for omega-3s may expose the body to harmful amounts of this toxic metal. Avoiding mercury is important for everyone, but especially for women during pregnancy and breastfeeding. For this reason, the best option for omega-3 fatty acid supplementation comes from plant-based sources, especially microalgae, which do not contain even trace levels of mercury. While there are reportedly sustainably-harvested sources of fish oil, mostly Norwegian cod, it's best to stick to plant-based sources for your omega-3 supplementation.

If you don't follow a plant-only diet, stick to wild-caught salmon, sardines, anchovies, and herring, which tend to be low in mercury and other contaminants and look at the Sustainable Seafood Guides available online.[17] Bivalves such as mussels, clams, and oysters may also provide a very good, low-mercury source of beneficial omega-3s.

How Much Omega-3s Do I Need?

If you do eat fish — such as wild salmon, sardines, anchovies, or herring — consume it no more than twice a week. Here is the Institute of Medicine’s recommendations for omega-3 adequate intake levels — these specifically refer to ALA (alpha linoleic-acid) because that is the only omega-3 that is essential and not produced by the body.

Age Male Female Pregnancy Lactation
Birth – 6 mo. 0.5 g 0.5 g N/A N/A
7 – 12 months* 0.5 g 0.5 g N/A N/A
1 – 3 years** 0.7 g 0.7 g N/A N/A
4 – 8 years** 0.9 g 0.9 g N/A N/A
9 – 13 years** 1.2 g 1.0 g N/A N/A
14 – 18 years** 1.6 g 1.1 g 1.4 g 1.3 g
19 – 50 years** 1.6 g 1.1 g 1.4 g 1.3 g
51+ years** 1.6 g 1.1 g N/A N/A

*As total omega-3s
**As ALA

Whether you get it from supplements or whole foods, 1.6 grams (1600 mg) daily of combined DHA and EPA is generally enough for men to maintain overall health, and 1.1 grams (1100 mg) for women.[18] Pregnant and breastfeeding women need an additional 300 milligrams per day, while a total of 500 milligrams per day is enough for an infant or child.[19]

Some health care providers may recommend higher levels of combined DHA and EPA per day, depending on the health concern.

The American Heart Association recommends you do not exceed three grams of fish oil supplement daily. However, you can safely take higher levels of plant-based supplements, or omega-3s from plant foods. Always consult with your doctor or healthcare provider before beginning a supplement regimen.

Side Effects of Fish Oil

Another reason people dislike fish oil is its side effects, which include:

Consuming extremely high doses of fish oil (over three grams) can have a side effect of bleeding (e.g., nosebleeds) and may increase the risk of hemorrhagic stroke.

To avoid these side effects, be sure to take fish oil with meals rather than on its own. Or, better yet, choose a plant-based alternative.

Should You Take a Supplement?

Some of the most compelling studies show that omega-3 fatty acids can reduce high blood levels of triglycerides for heart health, lower the risk of breast and colon cancer, and alleviate mood and anxiety disorders.

Supplements may be the best way to get servings of DHA, EPA, and ALA high enough to be effective for your particular health concern. If you decide to take a supplement, you can take these oils in the form of capsules or liquid. Plant-based omega-3 supplements offer the same beneficial DHA and EPA fatty acids as marine sources do for optimal health. If you insist on fish oil, choose organic, sustainably-harvested sources.

Points to Remember

While fish oil is a popular supplement with nearly 8 percent of the U.S. population taking it, fish oil may not be the best source of the omega-3 fatty acids DHA, EPA, and ALA. To satisfy the demand, fish are being depleted from the oceans in some regions. In addition, many of these fish contain high levels of mercury and other contaminants like PCBs, which pose health risks to humans, yet they are not regulated by federal agencies. The benefits of fish oil are due to the omega-3s they contain. These benefits include heart and cardiovascular health, brain health and mental wellness, and more. The best option if you want these benefits is to find a plant-based supplement, such as algae oil or to consume flaxseed, sesame seed, or other nuts with high levels of omega-3s.

References (19)
  1. Ghasemi Fard S, et al. "How does high DHA fish oil affect health? A systematic review of evidence." Crit Rev Food Sci Nutr. 2018:1-44.
  2. Mahaffey KR. "Mercury Exposure: Medical and Public Health Issues." Trans Am Clin Climatol Assoc. 2005;116:127-154.
  3. Alexander W. "Prostate cancer risk and omega-3 Fatty Acid intake from fish oil: a closer look at media messages versus research findings." PT. 2013 Sep; 38(9): 561–564.
  4. Bath‐Hextall FJ, Jenkinson C, Humphreys R, Williams HC. "Dietary supplements for established atopic eczema." Cochrane Database of Systematic Reviews 2012, Issue 2. Art. No.: CD005205.
  5. Wang C, Harris WS, Chung M, Lichtenstein AH, Balk EM, Kupelnick B, Jordan HS, Lau J. "n-3 Fatty acids from fish or fish-oil supplements, but not alpha-linolenic acid, benefit cardiovascular disease outcomes in primary- and secondary-prevention studies: a systematic review." Am J Clin Nutr. 2006 Jul;84(1):5-17.
  6. "n–3 Fatty Acids in Patients with Multiple Cardiovascular Risk Factors." N Engl J Med 2013 May; 368:1800-1808.
  7. National Center for Biotechnology Information. "Does fish oil lower blood pressure? A meta-analysis of controlled trials."
  8. McKenney JM, Sica D. "Prescription omega-3 fatty acids for the treatment of hypertriglyceridemia." Am J Health Syst Pharm. 2007 Mar 15;64(6):595-605. Review.
  9. Brinson BE, Miller S. "Fish oil: what is the role in cardiovascular health?" J Pharm Pract. 2012 Feb;25(1):69-74.
  10. Kuan-Pin Su, Yutaka Matsuoka, Chi-Un Pae. "Omega-3 Polyunsaturated Fatty Acids in Prevention of Mood and Anxiety Disorders." Clin Psychopharmacol Neurosci. 2015 Aug; 13(2): 129–137.
  11. Calder PC. "Marine omega-3 fatty acids and inflammatory processes: Effects, mechanisms and clinical relevance." Biochim Biophys Acta. 2015 Apr;1851(4):469-84.
  12. Gurzell EA, Teague H, Harris M, Clinthorne J, Shaikh SR, Fenton JI. "DHA-enriched fish oil targets B cell lipid microdomains and enhances ex vivo and in vivo B cell function." J Leukoc Biol. 2013 Apr;93(4):463-70.
  13. Bhargava R, et al. “A randomized controlled trial of omega-3 fatty acids in dry eye syndrome. Int J Ophthalmol. 2013; 6(6): 811–816.
  14. Georgiou T, Prokopiou E. "The New Era of Omega-3 Fatty Acids Supplementation: Therapeutic Effects on Dry Age-Related Macular Degeneration." J Stem Cells. 2015;10(3):205-15.
  15. Fabian C, Kimler B, Hursting D. "Omega-3 fatty acids for breast cancer prevention and survivorship." Breast Cancer Res. 2015 May; 17(1): 62.
  16. Brasky TM, Darke AK, Song X, et al. "Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial." J Natl Cancer Inst. 2013 Jul 10.
  17. "Printable Consumer Guides." Monterey Bay Aquarium Seafood Watch program. 2018. Accessed 26 Sep. 2018.
  18. European Food Safety Authority. "Scientific Opinion on the Tolerable Upper Intake Level of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA)." 2012 July.
  19. Omega-3 Fatty Acids: Fact Sheet for Health Professionals.” National Institutes of Health Office of Dietary Supplements. 6 Jun. 2018. Accessed 27 Sep. 2018.

†Results may vary. Information and statements made are for education purposes and are not intended to replace the advice of your doctor. If you have a severe medical condition or health concern, see your physician.


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