The Health Benefits of Fish Oil

Fish oil may ease symptoms of rheumatoid arthritis and depression

Woman holding fish oil supplement
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If you’re looking to get more omega-3s in your diet and you’re not a fan of eating fish, you wouldn’t be the first to consider a more convenient option: a fish oil supplement. According to figures from the National Institutes of Health, roughly 80%—or about 19 million Americans—take some kind of over-the-counter (OTC) fish oil supplement.

In addition to being more convenient, studies indicate that fish oil supplements are much less likely than fish to contain contaminants, due to the purification that occurs during the manufacturing process. Fish oil sold over-the-counter contains EPA and DHA, the two types of omega-3s found in fish.

Over-the-counter fish oil supplements are different than those prescribed for people with very high triglycerides, including Lovaza (omega-3 ethyl esters), Vascepa (icosapent ethyl), and Epanova (omega-3-carboxylic acids).

Health Benefits

Research suggests that fish oil may offer the following benefits.

Arthritis and Autoimmune Diseases

Fish oil has been found to be effective in the treatment of rheumatoid arthritis (RA) symptoms by reducing morning stiffness, joint tenderness, and the number of swollen joints and regulating the immune response. Fish oil can also help manage cardiovascular risk factors, which is important since people with RA are at an increased risk of a heart attack. 

According to the Arthritis Foundation, fish oil can also be used for:

  • Knee osteoarthritis
  • Lupus
  • Psoriasis
  • Raynaud’s syndrome

Heart Health

Although fish oil can’t prevent a heart attack or stroke, it is study-proven to reduce some of the risk factors associated with both of these conditions, including:

  • Increasing “good” HDL cholesterol
  • Lowering triglycerides
  • Slightly lowering blood pressure
  • Slowing the progression of atherosclerosis (hardening of the arteries)
  • Reducing abnormal heart rhythms or arrhythmias

If you are taking fish oil because you have high triglycerides, a type of fat associated with increased risk of heart disease, your doctor may prescribe a prescription fish oil like Lovaza for you. Prescription fish oil capsules contain highly purified fish oil with a greater concentration of omega-3 fatty acids than most over-the-counter fish oil capsules. 

Mental Health

Research has shown that fish oil, which is rich in the omega-3 fatty acids EPA and DHA, may be useful in the treatment of depression. Epidemiological studies suggest that either a deficiency of omega-3 fatty acids or an imbalance in the ratio of omega-6 and omega-3 fatty acids may be linked to increased rates of depression. Further, a handful of small, well-designed studies support the use of fish oil as an addition to antidepressant therapy.

Although more research is needed to determine effectiveness, fish oil has also been studied in the treatment of the following psychiatric disorders:

Possible Side Effects

The side effects of fish oil most often occur when people take the supplement in high doses (more than 3 grams per day). In other words, the more you take, the more you're likely to experience side effects, which is why it's important to consult with your healthcare provider prior to taking a fish oil supplement.

The most common side effects include:

  • Nausea
  • Diarrhea
  • Heartburn
  • Abdominal pain
  • Belching a fish-like aftertaste ("fish burbs")

High doses of omega-3 fats, found in fish oil supplements, can slow blood clotting and increase your risk of bleeding or bruising if you already taking an anticoagulant ("blood thinner") like Coumadin (warfarin) or Plavix (clopidogrel). It can also reduce the body's immune system, or ability to fend off infection.

Dosage and Preparation

How much fish oil you take will depend on your age, sex, and specific health condition, so it’s best to consult your healthcare provider before taking these supplements. Fish oil should be taken in whole-from capsules, with food and water, and not broken and sprinkled into food or liquids.

The Food and Drug Administration recommends consuming no more than 3 grams (3,000mg) per day of EPA and DHA combined, including up to 2 grams (2,000mg) per day from dietary supplements. Higher doses are often used to lower triglycerides, but you should only do so under the guidance of your healthcare professional.

High doses of fish oil can cause bleeding problems, especially if you are taking Coumadin (warfarin) or other anticoagulant medications, as well as problems with immune function.

It’s not yet known whether people who are allergic to seafood can safely take fish oil, according to the National Center for Complementary and Integrative Medicine.

What to Look For

Although fish oil is readily available at health foods and pharmacies, it is important to speak to your doctor before starting to take them. When purchasing a fish oil supplement, the best way to tell if a product is reputable is to read the label. Avoid any products that claim to "cure depression" or "reduce the risk of heart disease."

According to the Food and Drug Administration (FDA), it's illegal "to market a dietary supplement product as a treatment or cure for a specific disease, or to alleviate the symptoms of a disease."

Look closely for added ingredients like fillers, binders, and flavorings. The fish oil supplement should also contain a seal of approval from a third-party testing organization to demonstrate purity levels, notes the NIH. The big three include U.S. Pharmacopeia,, and NSF International. While this seal of approval does not guarantee that the fish oil is safe or that it will work, it does guarantee that there aren't harmful levels of contaminants and that the product contains the ingredients listed on the label.

Another way to tell high-quality fish oil is by its smell and taste. Fish oil should not smell or taste "fishy." If it does, this indicates that the fish oil is starting to degrade and is becoming rancid. A strong smell may also be a sign that artificial flavors were added to the product.

Of course, the best source of omega-3 fatty acids come from fish, especially wild fish that eat a lot of omega-3-rich algae. Smaller cold-water fish, such as herring, mackerel, salmon, and sardines, are your best choices. Larger fish and farmed fish may accumulate toxins in their tissues. Mercury, polychlorinated biphenyls (PCBs), dioxins, and pesticide residues are the toxins of greatest concern. At this time, however, the benefits of consuming fish outweigh the risks for most people.

Other good dietary sources of omega-3 fatty acids include the following:

  • Nuts and seeds (flaxseed, chia seeds, walnuts)
  • Plant oils (flaxseed oil, soybean oil, canola oil)
  • Fortified foods (eggs, milk, cereals, and orange juice)
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  1. Most Used Natural Products. Use of Complementary Health Approaches in the U.S.: National Health Interview Survey (NHIS). National Center for Complementary and Integrative Health. Updated September 24, 2017.

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