Doctors and dieticians have praised omega-3s for potentially reducing cardiovascular events for decades, making fish oil a popular nonvitamin, nonmineral dietary supplement in the United States.
Despite their widespread use, omega-3 supplements remain controversial; some studies tout their benefits, while others suggest they have no effect or could even be harmful.
What Are the Key Health Benefits of Omega-3 Fatty Acids?
Particularly noteworthy is the significance of dietary balance between omega-6 and omega-3 fatty acids. Studies generally seem positive when this balance is maintained, underscoring the crucial role of dietary equilibrium.

1. Reduce Heart Disease Risk
Omega-3 fatty acids have gained attention for their potential cardiovascular benefits. Despite a fatty fish-rich diet, these benefits were initially observed in Greenland Inuits with low cholesterol, triglycerides, and low-density lipoprotein (LDL) levels. Subsequent studies have produced mixed results. One 2019 study found that despite having a better blood lipid profile, the Canadian Inuit population had a higher prevalence of heart attack, stroke, diabetes, obesity, and hypertension than the general Canadian population.What Are the Benefits of Eating Fish?
A 2024 study examining nearly 200 blood samples found a 16 percent reduced risk of stroke due to DHA from fish consumption. Researchers of one 2004 meta-analysis concluded that the mortality rates from coronary heart disease might be reduced by consuming fish once or more per week. The meta-analysis showed that a 20-gram daily increase in fish consumption was associated with a 7 percent reduction in coronary heart disease mortality risk.Arguments for and Against Supplementing
Studies both supporting and opposing supplementation have been reported.Potential Harms From Supplementing
2. Lower Cancer Risk
Research findings on the potential of omega-3s to reduce cancer risk are also mixed. Research has associated high consumption of fish or fish oil in human populations with a reduced risk of colon, prostate, and breast cancers. However, other studies have not found a significant association or a slightly increased risk.Prostate Cancer
Regarding fish consumption, a 2021 meta-analysis of 5,607 men with an average follow-up of five years found consuming omega-3-rich fish did not affect prostate cancer risk. Although a 2010 meta-analysis noted a 63 percent reduction in death from prostate cancer among those who consumed fish, it also failed to divulge compelling evidence indicating a protective link between fish consumption and prostate cancer incidence.Breast Cancer
In several studies, increased consumption of long-chain omega-3 fatty acids is linked to a reduced risk of breast cancer. Among 35,298 women aged 45 to 74 in the Singapore Chinese Health Study (1993–1998), those with the highest three quartiles of long-chain omega-3 intake had a 26 percent reduced risk of breast cancer compared to those in the lowest quartile, following about five years of observation.Colorectal Cancer
A 2007 meta-analysis of 19 cohort studies found that fish consumption only slightly reduced overall colorectal cancer risk. However, among those with the highest fish intake (eating at least seven times more fish per month than those with the lowest intake), there was a 22 percent lower risk of colorectal cancer compared to the lowest-intake group.3. Maintain Mental Health and Cognitive Function
Low intake of marine omega-3s is linked to an increased risk of various mental health issues, including attention-deficit/hyperactivity disorder (ADHD), autism, bipolar disorder, depression, and suicidal thoughts. Omega-3s, in general, play a crucial role in promoting brain development and regulating behavioral and neurochemical aspects related to mood disorders, including stress responses, depression, and aggression, as well as dopamine-related content and function.- Depression: Multiple studies demonstrate the effectiveness of omega-3s in treating major depressive disorder and various psychiatric conditions. For instance, a 2023 study showed that combining an omega-3 fatty acid supplement with an antidepressant led to a significantly greater improvement in depressive symptoms compared to either the supplement or antidepressant alone.
- ADHD: Children require omega-3 fatty acids for proper brain development. A 2014 review of two meta-analyses concluded that children with ADHD tend to have lower levels of omega-3s, and supplementing their diet with them can lead to modest improvements in ADHD symptoms. Given the evidence, omega-3 fatty acids may be considered as an additional supplement to traditional ADHD treatments.
- Schizophrenia: While specific clinical interventions have demonstrated the efficacy of omega-3 PUFA supplementation in relieving symptoms and enhancing cognitive functions in schizophrenia patients, not all studies have shown the same results.
- Bipolar disorder: Bipolar disorder leads to extreme mood swings, characterized by mania or hypomania (emotional highs and lows) and depression. A 2014 study suggested that omega-3s appeared to be an effective supplementary treatment for both unipolar and bipolar depression.
- Alzheimer’s and age-related cognitive decline: A 2023 meta-analysis of 1,135 participants showed that long-term users of omega-3 supplements had a 64 percent lower risk of developing Alzheimer’s disease.
4. Improve Hyperlipidemia
Hyperlipidemia is characterized by high levels of lipids, such as cholesterol and triglycerides, in the blood. It is associated with atherosclerosis (artery hardening) and can lead to severe health issues, such as heart attacks and strokes. Omega-3s reduce plasma triglyceride levels, especially in individuals with hypertriglyceridemia.5. Manage Autoimmune Diseases
Omega-3s, especially EPA and DHA, have strong immunomodulatory effects. Research suggests that omega-3s possess anti-inflammatory properties, making them potentially beneficial for managing inflammatory and autoimmune diseases such as arthritis, Crohn’s disease, ulcerative colitis, and lupus.6. Support Healthy Bones and Joints
Evidence indicates that omega-3s are beneficial for bone health. A 2007 study found a positive association between omega-3s and higher bone mineral density in healthy young men. Research also suggests that omega-3s could be a promising treatment for osteoarthritis.7. Enhance Sleep Quality
A 2021 study found that DHA-rich oil supplementation in healthy adults who didn’t regularly eat oily fish significantly improved sleep efficiency and reduced the time it took to fall asleep compared to a placebo. Additionally, a 2022 study showed that DHA/EPA enhances sleep quality for individuals aged 45 and older, pointing out that these effects had already been observed in children and young adults.8. Promote Infant and Child Development
DHA is essential for infants’ growth and development of the central nervous system and visual function.9. Reduce Menstrual Pain
A 2012 study found that omega-3 fatty acid supplementation effectively reduced the severity of primary dysmenorrhea (painful menstruation) symptoms, reducing the need for ibuprofen as a rescue medication. Older research has also suggested that dietary supplements containing fish or seal oil, enriched with or combined with vitamin B12, could significantly alleviate menstrual discomfort.10. Alleviate Diabetes Symptoms
A 2015 meta-analysis reported that omega-3s had no significant effect on glucose control. However, when the omega-6:omega-3 ratio was lowered, a 2019 meta-analysis reported decreased insulin and insulin resistance in diabetic patients when supplementation was implemented for more than eight weeks.11. Lower High Blood Pressure
Some studies have determined that omega-3s can lower hypertension. A 2012 review suggested that high doses of omega-3s (at least 3 grams per day) can lower blood pressure, particularly systolic pressure, in older and hypertensive individuals. However, study results regarding dosage vary. One 2022 dose-response meta-analysis concluded that consuming around 2 to 3 grams of omega-3s daily is optimal for lowering blood pressure.12. Significantly Improve Rheumatoid Arthritis
An older clinical trial showed that daily fish oil supplements reduced morning stiffness and the number of tender, swollen joints in rheumatoid arthritis patients. These benefits were more pronounced with higher doses.13. Reduce Macular Degeneration Risk
Age-related macular degeneration (AMD) is a leading factor contributing to vision impairment in older people. Researchers believe that DHA, found in the membranes of retinal cells, and EPA, which produces beneficial compounds for the retina, could protect the retina and potentially prevent or slow AMD progression.14. Decrease Blood Clot Risk
Long-chain omega-3 fatty acids such as EPA and DHA can help prevent blood cells (platelets) from sticking together too much, which is good for heart health. Taking these fatty acids might lower the risk of bleeding during surgery, according to a 2018 study.Why Don’t Some of the Studies Agree?
- Dose-dependent effect: According to a 2023 review in Cardiovascular Research, most evidence shows that low-dose (1 gram per day or less) omega-3 supplementation does not significantly decrease the risk of cardiovascular events. Overall, higher doses of supplements may or may not provide health benefits and could lead to adverse effects, such as atrial fibrillation.
- Composition: Some studies use fish-sourced omega-3s, while others use fish oil containing both EPA and DHA. Others use only EPA or a highly purified form, while some studies do not provide a supplement. Instead, these studies rely on participants consuming an omega-3 supplement of their choice. This variation fuels ongoing debate about which form is most effective.
- Purity: According to a 2020 article, omega-3 supplements from U.S. stores had about a 50 percent chance of containing less omega-3 than stated on the label. If products have lower omega-3 fatty acid content than advertised, the dosage might be inadequate for achieving the desired outcomes in studies where supplement content wasn’t clearly labeled.
- Rancidity: Omega-3 supplements are highly susceptible to oxidation, which can change the structure of the fat, potentially reducing its effectiveness and leading to adverse health impacts. Eating rancid fat can lead to inflammation, organ damage, carcinogenesis, and advanced heart disease in animal studies, according to a 2013 review. The Guardian reported that independent tests by Labdoor found over 10 percent of fish oil supplements from 60 major retail brands were rancid, and nearly half were close to the maximum recommended limit. Two studies (1, 2) from 2015 mentioned in the 2020 article above revealed that oxidation was common, with 50 percent to 92 percent of store-bought supplements exceeding recommended cutoffs for markers of rancidity.
- Omega balance: Studies generally report benefits when the balance between omega-6 and omega-3 fatty acids is restored, highlighting the importance of a proper dietary ratio.
What Are the Types of Omega-3 Fatty Acids?
These fatty acids are vital for cell function, forming part of cell membranes to provide structure and support interactions. They are especially concentrated in the eyes and brain and crucial for eye, neurological, and psychological health. In addition, they provide energy and support the cardiovascular and endocrine systems.
- Eicosapentaenoic acid (EPA): Your body can utilize EPA directly in its original form. It is typically found in cold-water oily fish (e.g., salmon), algae oil, krill oil, and fish oil supplements.
- Docosahexaenoic acid (DHA): DHA is found in oily fish, seaweed, krill oil, algae oil, and omega-3 supplements. It is crucial for a healthy brain. Infants need DHA during their first six months for proper brain, eye, and nervous system development. Both EPA and DHA primarily originate from cold-water fish, earning them the name marine omega-3s. When consumed, the body converts some of the DHA back into EPA to maintain balanced levels of these essential fatty acids.
- Alpha-linolenic acid (ALA): ALA is considered a short-chain omega-3. ALA is found in certain plants, including green leafy vegetables, walnuts, flaxseeds, chia seeds, and industrial oils such as canola and soybean.
Supplements
Scientists agree that the best way to acquire omega-3 fats is from food. There is also general agreement on the importance of balancing omega-6 and omega-3 fatty acids. The ideal ratio of omega-6 to omega-3 fatty acids is approximately 2:1, according to a 2021 article. However, many Americans exceed a ratio of 20:1, which can contribute to cardiovascular and other diseases. This is because most people consume too many omega-6 fatty acids, mainly from refined vegetable oils, processed foods, and grain-fed meats. Omega-3 fatty acids, more prevalent in marine animals like fish and shrimp and plants like flaxseed and walnuts, are consumed in much lower quantities.Omega-3 supplements include marine- or plant-based oils and capsules. Synthetic and natural forms are also available, including dietary supplements of fish, krill, cod liver, and algal (vegetarian) oils.
These formulations can contain different omega-3 forms.
- Triglycerides: found in fish and other marine sources.
- Phospholipids: found in krill oil and some algal oils.
- Free fatty acids: These are individual fatty acids that are not attached to other molecules. They are released when triglycerides are broken down by an enzyme called lipoprotein lipase in fat tissue.
- Re-esterified triglycerides: These are generally more easily absorbed by the body than those in ethyl ester form.
- Ethyl esters: These have lower bioavailability than other natural forms of omega-3s.
- Not all omega-3 supplements are created equal. Choose a supplement that has been tested for heavy metals, rancidity, and purity.
- If you cannot eat fish or shellfish, consider kelp- or seaweed-based supplements with EPA and DHA.
- To avoid a fishy aftertaste from fish oil supplements, try freezing them before consumption, look for enteric-coated options, or take them with meals.
- Be cautious with supplements containing fish liver oil, such as cod liver oil. These can contain high levels of vitamins A and D that may be harmful if consumed excessively, especially during pregnancy.
- Ensure the supplement is stored in a dark container to protect the omega-3 fatty acids from exposure to sunlight, as they are prone to oxidation.
What Are the Signs and Symptoms of Omega-3 Fatty Acid Deficiency?
Current daily recommendations for omega-3 intake differ significantly, with no set allowances for DHA and EPA across age groups. Various organizations have recommended adequate omega-3 intake based on age, health, and other factors. The NHANES analysis revealed that all age and gender groups fell short of meeting these recommended intakes for EPA, DHA, and EPA+DHA. Therefore, omega-3 deficiency could be widespread in the United States.
- Dermatitis, or inflammation of the skin, which can cause symptoms such as redness, itching, swelling, and sometimes blistering or peeling
- Rough, scaly skin
- Dry eyes
- Inflammation
- Dry, brittle hair and hair loss
- Cognitive decline
- Joint pain and stiffness
- Muscle pain
- Depressive symptoms
- Digestive issues
- Allergies
- Poor brain development
- High triglycerides
What Are the Dietary Sources of Omega-3 Fatty Acids?
ALA is the predominant omega-3 fatty acid in many Western diets. It is present in chia and flax seeds, nuts (especially walnuts), leafy vegetables, some animal fats, especially from 100 percent grass-fed animals, and plant oils such as canola, soybean, and flaxseed oils.
- Herring
- Mackerel
- Salmon
- Cod
- Tuna
- Whitefish
- Sardines
- Anchovies
- Oysters
- Halibut
- Striped bass
- Rainbow trout
- Algae
- Chia seeds
- Hemp seeds
- Flaxseeds
- Walnuts (also high in omega-6)
- Fortified foods (e.g., certain eggs, yogurt, soy beverages, and infant formula)
Mercury in Fish
Certain fish have higher mercury levels than others. Species that primarily consume other fish—typically large, deep-sea fish—tend to accumulate mercury more quickly in their bodies. Here are some varieties that can contain elevated mercury levels:- King mackerel
- Marlin
- Orange roughy
- Shark
- Swordfish
- Tilefish
- Bigeye tuna
How Can I Optimize Omega-3 Fatty Acid Intake and Absorption?
- Pair omega-3s with a high-fat meal: Since omega-3s are fat-soluble, consuming them with dietary fat can enhance absorption. Pair omega-3-rich foods or supplements with a meal that includes healthy fats such as olive oil, avocados, or nuts.
- Limit omega-6 intake: High levels of omega-6s can potentially interfere with the body’s absorption and utilization of omega-3s, as both omega-3 and omega-6 fatty acids compete for the same enzymes in the body for metabolism. This is why maintaining a balanced ratio of omega-6 to omega-3 fatty acids is vital for optimal health. Limit omega-6-rich food intake by avoiding vegetable oils (e.g., corn, soybean, sunflower), processed foods, and livestock raised on grain.
- Avoid smoking and alcohol: Both smoking and alcohol consumption can contribute to oxidative stress in the body, which can impair omega-3 metabolism and change omega-3 concentrations.
- Choose the right cooking method: Generally speaking, boiling or baking fish can better preserve their omega-3s than frying or microwaving.
Which Nutrients Boost the Effects of Omega-3 Fatty Acids?
- Vitamin E: As an antioxidant, vitamin E protects omega-3s from oxidation, thus ensuring they remain effective in the body.
- Vitamin C: Vitamin C’s antioxidant effects safeguard omega-3s, leading to the belief that higher consumption of fatty acids should be paired with increased vitamin C intake.
- Zinc: Adding zinc supplements has been shown to boost the impact of omega-3 in lowering triglycerides and LDL levels in the bloodstream in diabetic patients. Additionally, consuming omega-3 in conjunction with zinc supplements can aid in decreasing inflammation.
What Is the Recommended Dietary Allowance of Omega-3 Fatty Acids?
- Birth to 6 months: 0.5 gram
- 1 to 12 months: 0.5 gram
- 1 to 3 years: 0.7 gram
- 4 to 8 years: 0.9 gram
- 9 to 13 years: 1.2 grams (males); 1.0 gram (females)
- 14 to 18 years: 1.6 grams (males); 1.1 grams (females)
- 14+ years (pregnancy): 1.4 grams
- 14+ years (lactation): 1.3 grams
- Over 19 years: 1.6 grams (males); 1.1 grams (females)
How Can I Test My Omega-3 Fatty Acid Levels?
What Happens if I Get Too Much Omega-3 Fatty Acid?
- Bad breath
- Gastrointestinal upset, including diarrhea
- Indigestion
- Stomach pain, nausea, or heartburn
- Potential for excess bleeding, such as nosebleeds
- Increased risk of atrial fibrillation
- Immune system slowdown
- Allergic reaction
- Hypomania, a mildly manic state that may occur in people with bipolar disorder
- Changes in blood sugar level
- Rash
- Severe dizziness
- Exhaustion of the body’s supply of antioxidants
Which Medications Interact With Omega-3 Fatty Acids?
- Chemotherapy medications: ALA has the potential to interact with certain chemotherapy drugs.
- Thyroid medications: ALA may decrease thyroid hormone levels.
- Diabetes medications: Someone who is diabetic, bruises easily, or is taking medication should speak with their doctor before consuming an omega-3 supplement.
- Blood-thinning medications: Warfarin may increase the anticoagulant effect of blood thinners, so people taking it should consult their doctor before taking omega-3 supplements.