- ω-3 fatty acids
- n-3 fatty acids
For Patients & Caregivers
How It Works
Omega-3 fatty acids have not been shown to prevent cancer.
Omega-3 fatty acids are obtained from fish oil. They have been used to protect against cardiovascular events such as heart attack. Studies have shown that omega-3 fatty acids can be taken up by the fatty deposits that line the arteries, thereby improving the stability of those deposits. They do not seem to affect blood clotting. Omega-3 fatty acids may also reduce inflammation by decreasing some of the signals that cells send to each other. It is thought that patients with colitis, asthma, cystic fibrosis and those before surgery may benefit from this reduced inflammatory effect. Omega-3 fatty acid supplements have been shown to be absorbed by the skin and protect it from ultra-violet radiation damage.
Findings from studies of omega-3 supplementation for cancer prevention are inconclusive.
To treat asthma
A review of published trials shows no effect of omega-3 on asthma.
To treat fatty deposits on the inside of arteries (atherosclerosis)
Studies have shown that omega-3 can increase the stability of these deposits, which may make them less dangerous.
To prevent cancer
Data on benefits of omega-3 for cancer prevention are not definitive.
To protect against cardiovascular disease
Studies have shown that omega-3 can reduce the frequency and severity of cardiovascular events such as heart attacks.
To improve the symptoms of colitis
Studies have shown that omega-3 may improve the symptoms associated with colitis.
To alleviate the symptoms associated with cystic fibrosis
One study showed an improvement in breathing parameters for patients taking omega-3 supplements, however other trials have shown no benefit. Larger studies are necessary to determine the actual effect.
To lower cholesterol levels
A review of published trials of omega-3 for lowering cholesterol levels in patients with diabetes found that while omega-3 lowered triglyceride levels, it also raised LDL cholesterol levels.
To treat symptoms of lupus
A small study found a reduction in symptoms of lupus in patients who took fish oil compared with those on placebo. More trials are needed to support this claim.
To alleviate depression
A study of a few thousand people in Finland found that people who ate less fish were more likely to have the symptoms of depression than those who ate more fish. Other studies have also shown a connection between omega-3 levels and depression scores, however few studies have attempted to determine if omega-3 supplementation affects depression symptoms.
Do Not Take If
You are taking Warfarin: Elevated INR has been reported when taken with fish oil supplements (2 g/day). INR decreased after reducing supplement intake.
High dose omega-3 supplements have been associated with subdural hematoma [6g/day] requiring craniotomy; and irreversible warfarin-induced coagulopathy following blunt head trauma.
- You are taking glucocorticoids: Omega-3 supplements worsened some side effects caused by glucocorticoids in a mice model. Clinical significance is not known.
For Healthcare Professionals
A type of polyunsaturated fatty acid (PUFA) derived mainly from fish oil, omega-3 fatty acids are used as a dietary supplement 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 other studies have shown that individuals with major depression have marked depletions in omega-3 fatty acids (2). However, omega-3 fatty acid supplementation did not 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 subsyndromal depressive symptoms in obese or overweight adults (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).
Supplementation with docosahexaenoic acid (DHA) improved learning and memory function in age-related cognitive decline (41). However in a large long-term study of omega-3 supplementation with or without multidomain lifestyle interventions of physical activity, cognitive training, and nutritional advice, there were no significant effects on cognitive decline in elderly adults with memory complaints (52). Consumption of fish oil during pregnancy also did not improve cognitive or language outcomes in early childhood (37) and does not improve intelligence (42). Other studies of omega-3 fatty acid supplementation and cognition in young children (6) and elderly subjects (7) are inconclusive.
Omega-3 fatty acid supplementation lowers cholesterol (8) (33) and may reduce recurrence in patients with a history of stroke (32). In individuals with cardiovascular risk factors, omega-3 supplementation improved cardiometabolic profiles (53). However, it does not lower the risk of cardiovascular disease events (9). Omega-3 may help patients with ulcerative colitis (10), but was ineffective in the treatment of Crohn’s disease (13). In adults with rheumatoid arthritis, reductions in NSAID use were reported after omega-3 fatty acid supplementation (14); Omega-3 may also be effective in reducing NSAID-associated gastroduodenal 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 trials using omega-3 fatty acids have shown possible benefits for patients with cystic fibrosis (21), but no benefit in those with asthma (22). Dietary supplementation with fish oil may help reduce the symptoms of systemic lupus erythematosus (24).
In type 1 diabetic patients, long-term omega-3 supplementation had positive effects on neuropathy, as 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 polyunsaturated omega-3 fatty acid consumption on insulin sensitivity and adipocyte function (45). However in a recent study among insulin-resistant adults, high-dose omega-3 supplementation did not improve features associated with metabolic syndrome such as adipose tissue lipolysis or inflammation (55). In another study, DHA was found more effective compared to eicosapentanoic acid (EPA) in modulating indicators of inflammation and blood lipids (50). In women with gestational diabetes, omega-3 fatty acids and vitamin E co-supplementation improved some markers of inflammation and oxidative stress as well as incidence of newborn hyperbilirubinemia (56).
In hemodialysis patients, omega-3 supplementation significantly reduced serum creatinine (57), but did not reduce arteriovenous fistula failure (58).
Data on omega-3 fatty acid supplementation for cancer prevention are inconclusive. It may reduce colon cancer risk (11) and improve immune response in patients undergoing colorectal cancer resection (12), 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). However, 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. But according to data from the Selenium and Vitamin E Cancer Prevention Trial (SELECT), high blood concentrations of omega-3 are 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).
Preliminary findings suggest that fish oil supplementation increases efficacy of chemotherapy, improves survival (38), and helps to maintain weight and muscle mass (39) in patients with non-small cell lung cancer (NSCLC). However in patients with gastric cancer, perioperative immunonutrition via an EPA-supplemented diet was not effective in reducing weight loss following total gastrectomy compared with a standard diet (59).
An EPA-enriched oral supplement improved tolerability of chemotherapy in patients with advanced colorectal cancer (40); and when combined with chemotherapy, fish oil supplementation may delay tumor progression in patients with colorectal cancer (49).
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 has been reported when taken with 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); and irreversible warfarin-induced coagulopathy following blunt head trauma (64).
- Glucocorticoids: Omega-3 supplementation 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 was found to decrease vitamin E and beta-carotene levels while increasing TNF-alpha (28).
- Conclusions of a meta-analysis indicate that high levels of omega-3s help reduce triglycerides, and increase LDL cholesterol (9).
- Doses higher than 3 grams per day may increase bleeding time (25).