Fish oil supplements: finding the one that's right for you

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As research on the potential health benefits of fish oil accumulates, fish oil supplement sales have skyrocketed. The varied benefits of fish oil are credited to two compounds that are classified as omega-3 fatty acids: eicosa-pentaenoic acid (EPA) and doeosahexaenoic acid (DHA). But with an abundance of choices on the market, how do you identify a superior fish oil supplement that contains potent amounts of these two substances without potential contaminants? Here's what you need to know.

Quality & Purity

One of the common concerns with fish oil supplements relates to product contamination, in particular the presence of polychlorinated biphenyls (PCBs), dioxins and heavy metals such as mercury. However, a recent report on fish oil supplements by ConsumerLab.com found no detectable levels of mercury (less than 1.5 parts per billion) in the products analyzed. Consumer Reports also recently tested several popular brands and found that none contained significant levels of mercury, dioxins or PCBs.

The lack of mercury in fish oil supplements may be attributed to the fact that most mercury in fish is concentrated in the meat, not the oil. This is especially good news for those taking high therapeutic doses to treat neurological disorders such as bipolar disorder, schizophrenia and depression. Distillation processes used by most manufacturers to remove contaminants may also explain the lack of heavy metals and other toxins.

One way to assess product purity and label accuracy of any supplement is to contact the company directly and request documentation of product verification by a third-party laboratory. Responsible companies that have done their homework and received good results will be more than happy to provide the information.

Many companies claim their fish oil is "pharmaceutical grade," creating the impression of superior quality and purity. However, there is no standard definition of pharmaceutical grade fish oil. Some companies base this claim on the concentrated potency of EPA and DHA in their products, while others emphasize a lack of impurities and contaminants.

Sources

Fish oil supplements are derived from a variety of sources, including mackerel, herring, tuna, salmon, cod liver, halibut, whale blubber and seal blubber. Cod liver oil is a potent source of EPA and DHA. While a tablespoon of cod liver oil provides approximately 500 milligrams (rag) of EPA and 500-700 mg of DHA, there are concerns of vitamins A and D toxicity if large doses are used long-term.

Vegetarian DHA supplements derived from algae oil are also available. Fish actually get their DHA by feeding on algae.

True Value

Is there a difference in quality and efficacy between fish oil supplements found at grocery and drug stores compared with the more expensive ones available at health food stores? Amounts and ratios of EPA and DHA vary significantly in supplements, but pricier fish oil supplements often have considerably higher potencies of EPA and DHA per capsule. A 1-gram softgel capsule purchased at a drug or grocery store typically provides 180 mg of EPA and 120 mg of DHA. More often than not, companies highlight the milligrams of fish oil on their labels when less than one-third of that listed amount is in the form of omega-3 fatty acids. The best way to determine the quantity of omega-3s is to add the amounts of EPA and DHA provided per serving. For example, a "1,000 mg fish oil" supplement containing 180 mg of EPA and 120 mg of DHA provides 300 mg of omega-3 fatty acids.

High-quality fish oil supplements found at health food stores are typically more concentrated in omega-3s, often supplying more than twice the typical dose of both EPA and DHA. And fewer pills translates to better compliance and results.

Not So Fishy ...

The unpleasant experience of a fishy aftertaste is likely the most common reason people elect not to take fish oil capsules. Fortunately, fairly recent industry developments have resulted in several products that are much more tolerable. For example, a number of companies offer flavored fish oil capsules. Some brands offer enteric fish oil capsules, which are coated with a substance that doesn't dissolve until exposed to an alkaline pH. This may provide the advantage of enhanced delivery and absorption in the small intestines by protecting long-chain fatty acids from hydrolysis in gastric acidity.

Rancidity & Oxidation

To prevent the harmful effects associated with free-radical toxicity, it is crucial to avoid consuming rancid fish oil (or any fat source). Fish oils are especially prone to spoilage. Most fish oil preparations contain small amounts of vitamin E, which may help minimize oxidation. As a fat-soluble antioxidant, vitamin E has the ability to counteract free radicals that damage cell membranes. And a high intake of polyunsaturated fats (such as fish oils) may increase the body's vitamin E requirements.

A practical strategy to check for rancidity is to simply smell the fish oil. If there's a strong fishy odor, the product is probably rancid. It is recommended that you store fish oil capsules in a cool, dry place away from sunlight. Refrigeration may not be necessary since the softgel capsule helps protect the oil from exposure to air (oxygen exposure accelerates oxidation). Even so, to be on the safe side, many manufacturers recommend refrigeration once the bottle is opened. All liquid fish oils require refrigeration upon opening.

Contraindications

Fish oil supplements generally produce few or no side effects at doses of 3 grams or fewer per day. Since fish oil has a slight blood-thinning effect (one of the proposed mechanisms for its heart-protective benefit), supplementation may increase the risks of bleeding, easy bruising and nosebleeds. Concomitant use of blood-thinning medications or herbs may also increase risks of bleeding. Supplementation with fish oil (along with other blood-thinning medications and supplements) should be stopped before surgery.

References:

1. www.consumerlab.com

2. www.uspverified.org

3. Natural Medicines Comprehensive Database

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6. Groff JL, Gropper SS. Advanced Nutrition and Human Metabolism, 3rd Edition. 2000; Wadsworth/ Thompson Learning.

7. Fritsche KL, Johnston PV. Rapid autooxidation offish oil in diets without added antioxidants. J Nutr. 1988 Apr; 118(4):425-6.

8. Pedersen HS, Mulvad G, Seidelin KN, Malcom GT, Boudreau DA. N3 fatty acids as a risk factor for haemorrhagic stroke. Lancet. 1999; 353:8123.

Minh-Hai Tran is a registered dietitian and certified clinical nutritionist. She graduated from Texas Christian University's nutrition and dietetics program in 2001, and she will earn her master's degree in nutrition from Bastyr University in June.

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