How Do I Tell Which Fish Oil To Take?

Omega-3 fatty acids EPA and DHA may reduce blood pressure, triglycerides and the risk of cardiovascular disease, according to the National Institutes of Health. The American Heart Association recommends you eat oily fish twice a week. If you have documented heart disease, take a fish oil supplement, advises the AHA.

EPA and DHA Content

The World Health Organization recommends that adults consume 300 to 500mg EPA plus DHA daily, reports the National Institutes of Health. When choosing a fish oil supplement, consider the amount of EPA and DHA per serving, suggests the University of Maryland Medical Center. A 5,000mg, or 5g, serving of fish oil contains about 170 to 560mg EPA and DHA. Other fatty acids present in fish oil supplements may not impart the same benefits that EPA and DHA do.

Purity

Larger fish that live longer, like shark or swordfish, may contain higher levels of contaminants than fish that are lower on the food chain, states a 2002 article in the journal "Circulation." Smaller fish, like anchovy or menhaden, likely contain lower levels of contaminants, such as mercury, PCBs and dioxins. Look for products that use third-party testing agencies to determine purity, such as ConsumerLab.com and International Fish Oil Standards. Fish oil supplements that are processed correctly generally contain negligible amounts of mercury, according to the NIH.

Safety

The NIH cautions against the use of fish oil if you are allergic to fish or seafood. Concomitant use of fish oil with blood-thinning agents, such as warfarin, aspirin, non-steroidal anti-inflammatory drugs and some herbal preparations, may increase the risk of bleeding. Chronic use of fish liver oil, such as cod, may cause toxicities of fat-soluble vitamin A and vitamin D. Limit your daily intake of EPA and DHA from supplements to 2g or less, cautions the U.S. Food and Drug Administration. Consume higher doses only under your doctor's supervision.

Side Effects

Fish oil supplements commonly cause gastrointestinal side effects, such as gas, bloating, nausea, diarrhea and fishy aftertaste. The University of Maryland Medical Center recommends a time-release, or enteric-coated, preparation to minimize these effects. Taking fish oil with meals, and gradually increasing the dose, will also help, says the NIH.

Other Considerations

If you have high triglycerides, your doctor may prescribe omega-3-acid ethyl esters, an FDA-approved medication made from omega-3 fish oil. Prescription fish oil contains a standardized amount of EPA and DHA in concentrated form. Since omega-3 fatty acids can spoil, freshness is important for both prescription and over-the-counter fish oil preparations. Purchase a container size that you will finish within a few weeks, and store it at room temperature, away from moisture and heat, instructs the NIH.