- ω-3 fatty acids
- n-3 fatty acids
For Patients & Caregivers
Tell your healthcare providers about any dietary supplements you’re taking, such as herbs, vitamins, minerals, and natural or home remedies. This will help them manage your care and keep you safe.
What is it?
What are the potential uses and benefits?
Omega-3 may be useful for:
- Reducing fatty deposits on the inside of your arteries
- Preventing heart disease
- Managing depression
- Lowering cholesterol levels
- Preventing cancer
- Treating symptoms of lupus (an autoimmune disease)
Omega-3 also has other uses that haven’t been studied by doctors to see if they work.
It’s generally safe to have omega-3 in your diet. Talk with your healthcare providers before taking supplements. They can interact with some medications and affect how they work. For more information, read the “What else do I need to know?” section below.
What are the side effects?
What else do I need to know?
- Omega-3 fatty acids and omega-6 fatty acids are not the same. Omega-6 is found in evening primrose oil and borage oil, and has different effects on the body.
- Don’t take omega-3 if you’re taking blood thinners such as aspirin, heparin, warfarin (Coumadin®, Jantoven®), clopidogrel (Plavix®), apixaban (Eliquis®), or rivaroxaban (Xarelto®). There are others, so be sure to talk to your healthcare provider before taking omega-3. Omega-3 can increase your risk of bleeding.
- Don’t take omega-3 if you’re taking glucocorticoids, such as cortisone, hydrocortisone or dexamethasone. Omega-3 supplements can worsen some side effects caused by glucocorticoids.
For Healthcare Professionals
A type of polyunsaturated fatty acid (PUFA) derived mainly from fish oil, omega-3 fatty acids are used as dietary supplements for depression, to lower cholesterol, and to reduce the risk of heart attack. A large survey of Finnish adults found that depressive symptoms were significantly higher among infrequent fish consumers (1) and in other studies individuals with major depression had marked depletions in omega-3 (2). Supplementation, however, did not prevent depression (77), relieve depression in adults with major depression (3), including those with or at risk of coronary heart disease (65), with mild to moderate depression (4), with perinatal depression (5); or in obese or overweight adults with subsyndromal depressive symptoms (66), and yielded mixed results in those with schizophrenia (23). But data from a randomized trial suggest that omega-3 may be useful in reducing the risk of progression to psychiatric disorders and as a safe preventive measure in young adults at risk for psychotic conditions (35).
Supplementation in pregnant women did not lower the incidence of early preterm delivery, nor the higher incidence of interventions in post-term deliveries (67), and did not improve cognitive or language outcomes in early childhood (37), or intelligence (42). But DHA was shown to improve learning and memory function in age-related cognitive decline (41) although a large, long-term study of omega-3 with or without multidomain lifestyle interventions of physical activity, cognitive training, and nutritional advice failed to find significant effects on cognitive decline in elderly adults with memory complaints (52).
Supplementation also did not have a significant effect on incidence or progression of age-related macular degeneration (73).
Omega-3 lowers cholesterol (8) (33) and may reduce recurrence in patients with a history of stroke (32). In individuals with cardiovascular risk factors, supplementation improved cardiometabolic profiles (53), but did not prevent incident atrial fibrillation (78) nor lower the risk of cardiovascular disease events (9) (72) although a meta analysis reported that the protective effects of EPA and DHA increase with dosage (79). Omega-3 may also help patients with ulcerative colitis (10), but was ineffective in the treatment of Crohn’s disease (13). In adults with rheumatoid arthritis, supplementation led to reductions in NSAID use (14); it may also be effective in reducing NSAID-associated gastro-duodenal damage (47). Other studies indicate that omega-3 may lower the magnitude of the body’s inflammatory response (18), and can reduce sensitivity to sunburn (20) and to ultraviolet radiation (44). Reviews of omega-3 trials have shown possible benefits for patients with cystic fibrosis (21), but no benefit in those with asthma (22). Supplementation with fish oil may help reduce the symptoms of systemic lupus erythematosus (24). Another large trial also reported benefit of omega-3 supplementation, with or without Vitamin D, in reducing the risk of autoimmune disease although the reductions were statistically insignificant (80).
In type 1 diabetic patients, long-term omega-3 supplementation had positive effects on neuropathy, measured by increases in corneal nerve fiber length (54). But among patients with dry eye disease, supplementation did not have a significant benefit (60). Findings of a systematic review support benefits of omega-3 on insulin sensitivity and adipocyte function (45). However, high-dose supplementation did not improve features associated with metabolic syndrome such as adipose tissue lipolysis or inflammation in insulin-resistant adults (55). In another trial, DHA was found more effective compared to eicosapentanoic acid (EPA) in modulating indicators of inflammation and blood lipids (50). In women with gestational diabetes, supplementation with omega-3 and vitamin E improved some markers of inflammation and oxidative stress as well as incidence of newborn hyperbilirubinemia (56). In hemodialysis patients, omega-3 significantly reduced serum creatinine (57), but did not reduce arteriovenous fistula failure (58).
Data on omega-3 for cancer prevention are inconclusive. It may reduce colon cancer risk (11); improve immune response in patients undergoing colorectal cancer resection (12); and reduce the incidence and severity of oxaliplatin-related neurotoxicity (74) but did not affect cancer outcomes (15) (43). Also, perioperative use of intravenous omega-3 resulted in infectious complications in patients undergoing elective colon resection for non-metastasized cancer (68). Conflicting data suggest beneficial association between higher omega-3 intake and improved survival among stage III colon cancer patients with wild-type KRAS and deficient MMR (69); supplementation was also associated with reduced occurrence of renal cell carcinoma in women (16). Furthermore, fish oil supplementation may lower the risk of breast cancer (36); improve overall survival (70) and xerostomia, but not toxicity (71) associated with neoadjuvant chemotherapy in patients with locally advanced breast cancer. According to data from the Selenium and Vitamin E Cancer Prevention Trial (SELECT), high blood concentrations of omega-3 were associated with increased risk of prostate cancer (17). In patients with sporadic colorectal neoplasia, EPA supplementation did not affect reductions in the proportion of patients with at least one colorectal adenoma when compared to aspirin or placebo (61). Also, in the prevention trial VITAL, supplementation did not lower incidence of invasive cancer or major cardiovascular events compared to placebo (62) although updated analyses show significant reduction in cancer mortality (75).
Preliminary findings suggest that fish oil supplementation increases efficacy of chemotherapy, improves survival (38), and helps maintain weight and muscle mass (39) in patients with non-small cell lung cancer (NSCLC); and improves quality of life scores in gastrointestinal cancer patients (81). But conflicting data suggest otherwise (59) (82) although a positive correlation was reported between adherence to supplementation and the ability to reduce weight loss during radiotherapy (83). Additional studies found an EPA-enriched oral supplement improved tolerability of chemotherapy in advanced colorectal cancer patients (40); and when combined with chemotherapy, fish oil supplements may delay tumor progression in those with colorectal cancer (49). Omega-3 supplements may also have a protective effect on the olfactory system in patients following endoscopic resection of sellar and parasellar masses (76).
Purported Uses and Benefits
Mechanism of Action
Omega-3 fatty acids are polyunsaturated fatty acids containing two or more double bonds in their acyl chain and a double bond on carbon number (3) (26). Changes in omega-3 fatty acid blood levels have been associated with cardiovascular disease and depression (27). The cardioprotective effects of omega-3 fatty acids likely are due its ability to be incorporated into and thereby enhance the stability of atherosclerotic plaques (26). Increasing the intake of polyunsaturated fatty acids has been shown to increase lipid peroxidation. Supplementation with omega-3 fatty acids, therefore, may increase oxidative stress on the body. Studies have shown that mucosal alpha-tocopherol levels decrease upon omega-3 fatty acid supplementation, which researchers believe may result from the body’s attempt to counteract the added oxidative burden (11). Besides reducing serum antioxidant levels, little is known about how this added oxidative stress affects the body.
Omega-3 fatty acid supplementation has been shown to decrease IL-6 (18) and tumor necrosis factor-alpha (28) levels while leaving most other mononuclear cell functions unaffected (29). Omega-3 fatty acids may also reduce inflammation in patients with ulcerative colitis by reducing rectal dialysate leukotriene B4 (10). Because of their anti-inflammatory effects, omega-3 fatty acids were thought to benefit patients with asthma (22) and cystic fibrosis (21), but data are inconclusive.
Increasing PUFA intake in pregnant women increases PUFA concentration but not cytokine concentration in human milk (30). Omega-3 fatty acid supplementation provides protection against ultra-violet radiation-induced erythema and p53 expression, a biomarker of DNA damage (20).
Warfarin: Elevated INR was reported following use of fish oil supplements (2 g/day). INR decreased after reducing supplement intake (34).
High dose omega-3 supplements have been associated with subdural hematoma [6g/day] requiring craniotomy (63);
Irreversible warfarin-induced coagulopathy was reported following blunt head trauma (64).
- Glucocorticoids: Omega-3 supplements potentiated some adverse effects of glucocorticoids in a murine model. Clinical relevance is not known (46).
Herb Lab Interactions
- In a study of heart transplant recipients, omega-3 supplementation decreased vitamin E and beta-carotene levels while increasing TNF-alpha (28).
- A meta-analysis found high levels of omega-3s to help reduce triglycerides, and to increase LDL cholesterol (9).
- Doses higher than 3 grams per day may increase bleeding time (25).