Do you know _all_ the health benefits of fish oil?

By Melissa Sammy, MDLinx
Published June 27, 2019

Key Takeaways

US adults are not meeting the recommended levels for omega-3 fatty acid intake—and it’s killing them. In fact, omega-3 fatty acid deficiency was ranked as the sixth highest killer of Americans, causing an average of 84,000 deaths annually, according to a study conducted by Harvard University researchers and colleagues.

These deaths were considered preventable, given that adequate dietary amounts of omega-3 fatty acids have been shown to reduce the risks of some common causes of mortality. Because the body cannot produce omega-3 fatty acids on its own, it must be obtained from food—notably, seafood. Fatty fish, such as salmon and sardines, are perhaps the most potent dietary sources of these substances. The American Heart Association (AHA) recommends eating a 3-oz serving of oily fish at least twice weekly to get the full heart-healthy benefits from omega-3 fatty acids.

This level of intake, however, can quickly cut into a budget.

Incorporating fish-oil supplements into your diet can be a great way to get all of the heart-health benefits of omega-3 fatty acids at a low cost. Fish-oil supplements may also be good alternatives for vegetarians as well as those who are concerned about the mercury levels often found in seafood. When choosing a fish-oil supplement, make sure it contains eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—two essential omega-3 fatty acids that have been linked to positive effects on cardiovascular health problems.

With this in mind, let’s take a look at some of the powerful, scientifically documented health benefits of fish oil.

Epileptic seizures

About one-third of epileptic patients are unable to achieve seizure control with available drugs; among those who do, many experience adverse drug effects. Numerous experts have demonstrated the safety, efficiency, and cost-effectiveness of fish oil for the treatment of refractory epilepsy.

In one small but notable study, low-dose fish oil significantly reduced seizure frequency in patients with drug-resistant epilepsy. Participants received a daily regimen of either placebo, high-dose fish oil (2,160 mg), or low-dose fish oil (1,080 mg) over 42 weeks (three 10-week treatment periods, two 6-week washout periods). Low-dose fish oil reduced the incidence of seizures in participants by nearly 34% vs placebo.

Interestingly, participants who received high-dose fish oil did not demonstrate any significant reduction in seizure frequency. Furthermore, in the low-dose fish-oil group, two patients achieved seizure freedom during their 10-week treatments compared with no patients in either the high-dose fish-oil or placebo groups. In addition, participants in the low-dose fish-oil group exhibited a decrease in blood pressure levels vs those in the high-dose fish-oil group—who actually showed a small increase.

“We don’t completely understand why low dose works and higher doses do not, but there is evidence from animal studies that high doses are counterproductive. The response to fish oil at low dose for both seizures and depression has substantial implications for use, given the common propensity for individuals to self-dose with an ‘a little helps, a lot should help much more’ thought process,” remarked lead study author and principal investigator Christopher M. DeGiorgio, MD, professor, Departments of Neurology, Cardiology and Neurobiology, UCLA School of Medicine, Los Angeles, CA.

Neurocognitive injury and impairment

Because DHA comprises about 30% of all brain matter, it has been broadly studied in the literature for its role in neurocognitive health.

In a study published in PLOS One, researchers found that omega-3 fish oil—specifically the component DHA—may help to protect against chronic alcohol-related brain damage and the subsequent risk of dementia. DHA exhibited protective effects against neuroinflammation and neuronal cell death in rat brain cells exposed to high levels of alcohol. In all, there was up to 90% less neuroinflammation and neuronal death in brain cells exposed to alcohol plus DHA than in cells exposed to alcohol alone.

“Fish oil has the potential of helping preserve brain integrity in chronic alcohol abusers,” concluded principal investigator and coauthor Michael A. Collins, professor, Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Stritch School of Medicine, Maywood, IL. However, he noted that further studies are warranted to confirm the neuroprotective effects of fish oil against alcohol-related brain damage.

In another study involving an experimental model of acute ischemic stroke, investigators found that DHA may protect brain tissue and facilitate recovery—even when treatment is delayed by 5 hours. DHA reduced neurological deficits and swelling, and promoted neurobehavioral recovery. In all, DHA treatment not only salvaged brain tissue that would have died, but actually rendered some areas indistinguishable from normal tissue by 7 days via its mechanisms of repair.

“We are just now beginning to understand the significant impact of omega-3 essential fatty acids on stroke,” noted senior author Nicolas G. Bazan, MD, PhD, professor, Departments of Ophthalmology, Biochemistry and Molecular Biology, and Neurology, Louisiana State University Health Sciences Center, New Orleans, LA. “There is no simple solution just yet, but each new discovery brings us closer to defeating stroke and other debilitating neurodegenerative diseases.”

Fish-oil consumption has also been touted as an effective way to improve memory, particularly in older adults. In one systematic review and meta-analysis, adults with mild memory complaints who took DHA supplementation, either alone or in combination with EPA, demonstrated significant improvements in memory function outcomes, particularly episodic memory. Furthermore, investigators who conducted a trial across 19 US clinical sites with 485 participants, published in Alzheimer’s & Dementia, found that 24-week treatment with DHA supplementation (900 mg/d) improved learning and memory function in adults with age-related cognitive decline.

Vision loss

As with the brain, omega-3 fatty acids are an integral component of eye health. While fish oil may not necessarily benefit those with dry eye diseases—according to a large trial funded by the National Eye Institute—it may be an effective therapeutic option for those with more problematic eye conditions, such as age-related macular degeneration (AMD), which has been extensively covered in the literature.

For instance, in a pilot study of  the efficacy of fish oil for the treatment of AMD, regular high doses of omega-3 fatty acids (3.4 g EPA, 1.6 g DHA) for 6 months resulted in significant improvements in vision acuity in 100% of patients within about 19 weeks. Moreover, in a recent review of the impact of diet and food consumption on AMD, researchers identified five studies in which high omega-3 fatty acid consumption was strongly associated with decreased development of intermediate and late AMD.

Body weight and fat reduction

In several high fat diet-fed obese animal models, fish oil was associated with reductions in body weight and fat, leading researchers in recent years to study the potential anti-obesity effect of fish oil in humans. In some studies, fish-oil supplements helped to reduce waist circumference and abdominal fat, and contributed to weight loss in combination with diet and exercise.

Researchers of a study published in the American Journal of Clinical Nutrition found that fish-oil supplements in combination with regular exercise reduced both body fat and improved cardiovascular and metabolic health in a cohort of overweight individuals with high blood pressure, cholesterol, and triglyceride levels.

In another randomized clinical trial that included young overweight men, fish oil intake as part of an energy-restricted diet resulted in ~2-lb greater weight loss after 4 weeks than a similar diet that did not include seafood or marine supplements. Furthermore, via a meta-analysis of 21 randomized, controlled trials, researchers concluded that overweight or obese individuals may benefit from taking fish-oil supplements—especially when combined with life modification intervention, including exercise—for abdominal fat reduction.

Cardiovascular health

The benefits of fish oil on heart health have been widely studied and validated in clinical use.

According to experts at the Mayo Clinic, fish-oil consumption may help to reduce the risk of heart attack and stroke, and regulate triglyceride and blood pressure levels. Researchers have shown that taking fish-oil supplements for ≥ 6 months may reduce the risk of myocardial infarction and mortality in people at high risk for heart disease. Moreover, people who have experienced a heart attack or heart failure may benefit from fish-oil supplements. In a study conducted by the AHA, researchers found that omega-3 fish-oil supplements may help to prevent heart disease in patients who have had a recent heart attack and may even prevent death and hospitalization in patients with heart failure.

“Scientific findings from the past two decades that focused on the prevention of cardiovascular diseases continue to show that among people who are at risk of dying from heart disease, the potential benefit of omega-3 fish oil supplements is still useful for people who have had a recent heart attack, which is consistent with the 2002 statement,” said lead study author David S. Siscovick, MD, MPH, chair of the AHA Council on Epidemiology and Prevention. “What is new is that people with heart failure also may benefit from omega-3 fish oil supplements.”

Important considerations

Although fish oil is generally safe, excess consumption can increase the risk of bleeding events and may suppress immune response. Therefore, supplements should only be taken under physician supervision. Furthermore, people with shellfish allergies should avoid taking fish-oil supplements unless otherwise directed by their physicians, since it is unclear whether these supplements may trigger allergic reactions.

The following drug interactions should also be considered, according to Mayo Clinic experts:

  • Anticoagulant and antiplatelet drugs, herbs, and supplements. These drug types, herbs, and supplements reduce blood clotting—thus taking fish-oil supplements in combination with them may increase the risk of bleeding.
  • Blood pressure drugs, herbs, and supplements. Taking fish-oil supplements may decrease blood pressure levels, and taking these supplements with blood pressure drugs may amplify the effects on blood pressure.
  • Contraceptive drugs. Some contraceptives may interfere with the effect fish oil typically has on triglyceride levels.
  • Orlistat. Taking fish oil with this weight-loss drug may reduce absorption of fish-oil fatty acids. Consider taking the supplement and drug 2 hours apart.
  • Vitamin E. Taking fish oil can reduce vitamin E levels.
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