Dietitians Explain the Truth About Taking Fish Oil

omega 3 fish oil capsules and a glass bottle on a beige background
What You Need to Know Before Taking Fish Oil Tanja Ivanova - Getty Images

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What if there was something you could eat naturally or take as a supplement that could lower your risk of heart disease, improve your cognitive health and may even reduce your anxieties? It sounds almost too good to be true, but there is good reason to believe that it is already here, affordable and widely available: fish oil.

One of the biggest health benefits of consuming fish comes from the polyunsaturated omega-3 fatty acids. Oily fish, such as salmon, sardines, anchovies, mackerel, rainbow trout and herring have the highest amount of omega-3 fatty acids. While diet first is always the recommended way to reap the benefits, if you are not a fish lover or don't consume enough fish in general, there are many supplement forms available to boost your overall intake.

Here we explain the benefits of including more fish and fish oil in your diet, and recommendations on supplements, as well as risks and contraindications.

What is fish oil?

Fish oil is derived from fatty fish and is a source of omega-3 fatty acids. "The fish oil found in supplements are extracted from the tissues of oily fish, and put into capsule form," according to cardiology dietitian Michelle Routhenstein, MS, RD, CDE, CDN, at

"The active ingredients in fish oil supplements are omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both EPA and DHA provide health benefits," she adds. "EPA has been shown to help reduce inflammation, reduce symptoms of depression and may help reduce hot flashes during menopause. DHA has been shown to play an important role in brain health, eye health and reducing triglyceride levels."

The Dietary Guidelines for Americans and the American Heart Association recommends consuming two servings (8 ounces) of fish every week. To avoid high mercury exposure, it is recommended to choose fish such as salmon and sardines. In addition to providing omega-3 fatty acids, fish consumption provides other heart healthy nutrients such as selenium, vitamin D and vitamin E.

soft capsules of fish oil with omega 3 and vitamin d on a golden background
Tanja Ivanova - Getty Images

Fish oil health benefits

Fish oil, and specifically omega-3 fatty acids, have been associated with a wide range of health benefits. Here are some of the top health conditions that it may improve.

  1. It may improve heart health: "Omega-3 fatty acids have been shown to help lower the risk of fatal heart attacks by about 9%," according to Routhenstein. This may be due to "reducing inflammation to lowering triglycerides, which can influence plaque build up and stability which is a main cause for heart attack risk," she adds. Additionally, "high dose fish oil has been so effective at lowering triglyceride levels by 30% or more, that a high dose prescription drug is now available for individuals with very high triglyceride levels."

  2. It may reduce inflammation: "When your body is in an overactive inflammatory state, you are at higher risk for diseases we’re all trying to avoid, like cancer, heart disease, type 2 diabetes, arthritis and brain disorders," according to registered dietitian Samantha Cassetty, MS, RD, nutrition and wellness expert and co-author of Sugar Shock. The omega-3 fats that fish oil contains, "can help blunt this process by inhibiting inflammatory compounds in the body," Cassetty adds. "A 2019 review of studies found that omega-3 supplements, including DHA and EPA lowered inflammatory markers among people with diabetes and heart disease. Another study found these fats also increase the level of anti-inflammatory molecules in the blood," she explains. "However, whether or not these anti-inflammatory benefits translate into benefits for heart disease and other conditions is still being debated," says Cassetty, although the evidence for eating seafood is clearer.

  3. It may improve cognitive function: More recently fish oil has been associated with a sharper mind, and studies show that supplementation with omega-3 fatty acids may have a positive effect on cognitive function. According to Routhenstein, "Omega-3 fatty acids, particularly DHA, is very prevalent in the brain and is therefore important in brain and cognitive function. Dietary deficiencies in omega-3 fatty acids are associated with various cognitive disorders such as dementia and ADHD."

  4. It may improve bone health: Observational studies have shown that omega-3 fatty acids may have a positive influence on bone mineral density, although according to Routhenstein, "there is not enough conclusive evidence that omega-3 fatty acids alone would improve bone health." She adds, "the possible proposed mechanism of why omega-3 fatty acids may be helpful is due to the anti-inflammatory factors that can prevent calcification and bone demineralization."

  5. It may help with mental health conditions: There’s evidence that supplementing your diet with fish oil may help improve symptoms of depression. According to Cassetty, "A 2019 review of studies concluded that EPA (but not DHA) had beneficial effects on depression." She adds, "the inflammatory process is involved in the development of depression, and fish oil helps by downgrading inflammation. There may also be additional factors involved, such as improving the communication of mood-regulation neurotransmitters." Additionally, "there is evidence that omega-3 fish oils may help relieve symptoms of anxiety. Fish oil may interfere with the biological mechanisms, such as inflammation, that promote anxiety, which may explain the improvements in anxiety symptoms," according to Cassetty.

  6. It may improve insulin sensitivity: Research suggests that short-term fish oil supplementation may improve insulin sensitivity. According to Cassetty, "longer treatment wasn't effective and fish oil doesn't appear to be effective in people without metabolic syndrome." Cassetty explains, "abdominal fat releases inflammatory markers, which is why fish oil may be helpful for improving insulin sensitivity in individuals that suffer from this condition."

  7. It may support pregnancy: According to the United States Food and Drug Administration (FDA), it is recommended that pregnant women should aim for up to three servings (12 ounces) of lower-mercury seafood a week because, as Cassetty explains, "fish oil can help the baby’s brain and eye development." She recommends, "if you can't hit that mark, talk to your doctor about whether a fish oil supplement is a suitable replacement." She adds, "beyond that, there isn't evidence that fish oil will help improve pregnancy outcomes."

  8. It may benefit skin health: According to Cassetty, "the omega-3 fats in fish oil help support and maintain the skin’s normal structure and barrier. Since sun damage causes inflammation, fish oil may help provide internal support against the sun’s damaging rays (but you still need sunscreen with appropriate SPF)." Cassetty explains, "since sun damage is involved in skin aging, fish oil could potentially help maintain more youthful skin, but the evidence is stronger for omega-3s from food than supplements."

  9. It may support eye health: Fish oil is associated with maintaining a healthy retina, but the evidence for taking a fish oil supplement for eye health is mixed. Cassetty explains, "some studies have suggested that fish oil may help relieve dry eye syndrome, but a large, year-long study found no difference between a supplement and a placebo. And fish oil supplements don't seem to have a beneficial effect on age-related macular degeneration, a leading cause of blindness in adults." More studies are needed to make a recommendation.

Fish oil supplements

Fish oil in both liquid and capsule forms can be equally effective, the choice depends on individual preferences. While both forms can leave an aftertaste, many supplements are now flavored with lemon or mint to alleviate that. Dividing doses can also help to reduce the taste, although fish oil in the liquid form may be difficult for some people to swallow with or without the added flavors or dividing of doses.

According to Routhenstein, the Global Organization for EPA and DHA Omega-3s (GOED) has established EPA + DHA daily intake recommendations based on a thorough review of the research. For the general population, and in order to lower the risk of coronary heart disease, 500mg of EPA + DHA daily is advised. For pregnant and lactating women, at least 700mg/day of EPA+DHA, with at least 300mg of the total being from DHA. Individuals with certain health conditions, such as high triglycerides, may need more than 1 gram per day.

The FDA does not approve supplements for safety and effectiveness, so we recommend choosing brands that have been tested by a credible third-party for purity, potency and safety. Select brands that are verified by USP and NSF and carry their individual seals, or ones that are granted by an independent, third party organization, such as Consumer Lab, that asserts quality control via purity tests and ingredient fact-checking. Additionally, while fish oil is typically available in a supplement form, if you prefer to get your omega-3's by eating fish, an easy way to remember the best types of oily fish to consume, is the acronym S.M.A.S.H which stands for: salmon, mackerel, anchovies, sardines, herring.

When introducing any new supplement into your diet you should always first consult with your healthcare provider.

Fish oil side effects

Side effects from supplementing with fish oil are often mild, and can include a disagreeable taste, headache and gastrointestinal symptoms such as heartburn, nausea, and diarrhea, according to the National Institutes of Health. Additionally, according to Routhenstein, "It is important to note that taking above 1 gram of fish oil per day was associated with an increased risk of atrial fibrillation, a common heart rhythm disorder that increases your risk of blood clots and strokes, according to this meta-analysis of randomized controlled trials."

Fish oil also naturally contains anticoagulant properties, and can therefore interact with blood clotting and blood thinning medications and may be contraindicated due to increased the risk of bleeding. Therefore, it is important to discuss with your healthcare provider before adding it to your dietary regimen.

The bottom line: You can maximize your intake of omega-3 fish oil by eating oily fish and supplementing with fish oil if you don't consume enough fish or if you are not a fish lover. Eating fish may have equal or in some cases superior benefits to supplementing with fish oil although stick with low mercury fish such as salmon, anchovies, sardines and herring. Fish oil has been associated with multiple health benefits including fighting inflammation, improving heart heart health, and cognitive function among many others. Always check with your healthcare provider before adding a new supplement to your diet.

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