How many of you are like myself and take fish oil or flax oil supplements? This is one of the world’s most popular supplements, as many have heard about the health benefits of the main ingredient, omega-3 fatty acid (DHA and EPA). But just how effective is omega-3, and for what diseases? Let’s look at the best evidence — there’s a lot to review.

First, the National Center for Complementary and Alternative Medicine has a nice review of Omega-3 that readers should check out. Here’s their piece on the research:

Status of Research on Omega-3s:

Epidemiological studies done more than 30 years ago noted relatively low death rates due to cardiovascular disease in Eskimo populations with high fish consumption. Since these early studies, numerous observational and clinical trials have studied fish oil and omega-3 fatty acids for a wide variety of diseases and conditions. Overall, the evidence appears the most promising for improving cardiovascular disease risk factors. For example, studies show that increasing levels of DHA and EPA—either by eating fish or taking fish oil supplements—lowers triglycerides, slightly lowers blood pressure, may slow the progression of atherosclerosis (hardening of arteries), and may reduce the risk of heart attack, stroke, and death among people with cardiovascular disease.

Several small studies have also found that fish oil may benefit people who have rheumatoid arthritis (RA). High doses of fish oil significantly reduced RA patients’ morning stiffness, number of swollen joints, and need for corticosteroid drugs.

Additionally, omega-3s have been studied for conditions such as asthma, dementia, diabetes, inflammatory bowel disease, lupus, osteoporosis, and renal disease, as well as organ transplantation outcomes (e.g., decreasing the likelihood of rejection). However, more research is needed before conclusions can be drawn about these conditions.

The always-useful Prescriber’s Letter has a nice patient handout on omega-3 (Detail-Document on Omega 3: Prescriber’s Letter). Here are some highlights:

What are omega-3 fatty acids?

Omega-3 fatty acids include eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), found in fish, and alpha-linolenic acid, found in soy, canola oil, flaxseed, and English walnuts.

For what conditions are omega-3 fatty acids effective?

There is good evidence that omega-3 fatty acids, particularly EPA and DHA, prevent heart disease. In people who already have heart disease, they help prevent death, heart attack, and stroke. They also reduce triglycerides. Omega-3 fatty acids might also help rheumatoid arthritis, high blood pressure, depression, bipolar disorder, menstrual pain, and certain kidney problems.

What is the best source of omega-3 fatty acids?

The best source of omega-3 fatty acids is fatty fish, like salmon. The American Heart Association (AHA) recommends that everyone eat at least two fatty fish meals (baked or broiled) weekly for cardiovascular health. People who have heart disease should try to eat fatty fish daily. Also add foods rich in alpha-linolenic acid (canola oil, soy, English walnuts, flaxseed) to your diet. But they are not good substitutes for fish because they do not provide enough EPA/DHA. Fish oil capsules are a convenient way to get your omega-3 fatty acids, especially if you need high doses. Fish oil capsules are sold over-the-counter or by prescription (Lovaza [formerly Omacor] in U.S.). Ask your healthcare provider if fish oil capsules are right for you.

Should I be concerned about mercury in fish?

Women who are pregnant or may become pregnant or are breastfeeding, and young children are at risk of mercury toxicity from certain fish. The EPA (U.S.) and Health Canada have specific recommendations for which fish these at-risk persons should avoid or limit. Fish low in mercury include shrimp, canned light tuna (not albacore), salmon, pollock, and catfish. Fish oil capsules are generally low in mercury and other pollutants. For more information, see http://www.epa.gov/waterscience/fishadvice/advice.html (U.S.) http://www.hc-sc.gc.ca/fn-an/securit/chem-chim/environ/mercur/cons-adv-etud-eng.php. (Canada).

How do I choose a fish oil product?

Over-the-counter fish oil is considered a supplement, not a drug, so quality and content varies. Choose products with the “USP Verified Mark” on the label. These have been tested, and have acceptable levels of mercury, other heavy metals, PCBs, and dioxins. They are confirmed to contain what the label says they contain. The omega-3 content is the labeled amount of DHA plus EPA.

Other data from Prescriber’s Letter:

Low Cholesterol: “Omega-3 has a lot of good data that it lowers cholesterol. Clinical research shows that taking fish oil in doses of up to 1-5 grams/day can reduce triglycerides by as much as 20% to 50%. But keep in mind that it is NOT effective for lowering total cholesterol or LDL-C. In fact, some people have a slight increase in LDL-C while taking fish oil. But they also tend to have a slight increase in HDL-C. Overall, the benefit outweighs the risk.”

High Blood Pressure: “there is relatively little evidence available on the use of fish oil specifically for hypertension.”

Heart Disease: “There is good evidence that routinely eating fatty fish, such as salmon, can reduce the risk of heart disease and all-cause mortality.”

My Bottom Line

I think there’s strong evidence that omega-3 helps lower heart disease risk and overall mortality, even in healthy groups such as myself, which is why I take it. Side effects in the stomach are usually minimal. However, the medical community is not in unison regarding omega-3 as a wonder-pill, at least in terms of supplements. Most people should be able to get enough omega-3 simply from eating a lot of fatty fish (salmon, mackerel, sardines), at least twice a week. This should be everyone’s first choice; those of you who hate fish, or are worried about mercury and other contaminations in your fish, should be the ones to consider a supplement.

As for which supplement to buy, be very careful about not getting a cheap supplement which may be contaminated with mercury or simply may not have enough omega-3. Stick to top brands, or try to stock up at home each year.

And just as importantly for those who take supplements: make sure your total daily intake of omega-3 DHA and EPA is at least 1 gram a day. Bottles may say something misleadingly impressive like “one gram of fish oil per pill”, but the crucial ingredient is on the back label: the total amount of omega 3 (DHA + EPA) is the key! So, if your pill has 500mg total DHA and EPA, then you’d take it twice a day.

One more thing: stick to fish oil and not flax oil. Flax oil doesn’t have enough of the DHA and EPA, which are much more potent than the omega-3 ALA that predominates in flax oil.