Fish-oil supplements on the market

Fish-oil supplements come in a variety of forms. Cod-liver oil is the original article, but its disadvantages relative to omega-3 capsules include low ratio of EPA/DHA to overall calories, greater risk of mercury and PCB contamination, and potential for vitamin A and D toxicity with high levels of supplementation.

Most fish-oil capsules are free of significant mercury and PCB contamination, and industry standards for monitoring and disclosure are relatively stringent. Disparities exist, however, in the amount of active EPA and DHA delivered per capsule, and some ultra-discounted brands may be of dubious benefit due to the sheer number of capsules required to achieve clinically meaningful supplementation.

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Manufacturers sometimes use the term “pharmaceutical grade” to imply greater potency or purity, but the claim is not regulated and almost meaningless. Also, controversy persists over relative advantages of two competing technologies for enhancing the EPA/DHA concentration: triglyceride substitution vs. ethyl esterification (used in Lovaza). Each camp claims superior bioavailability, but evidence remains inconclusive.

Finally, new formulation technology permits the offering of EPA/DHA in variable ratios designed to target specific clinical goals. EPA and DHA may have differing effects on desirable cardioprotective endpoints. The precise “optimal” ratio of EPA/DHA for heart disease prevention, if such a thing exists, has not yet been determined.

Uncertainty remains among health-care professionals as to the potential therapeutic application of fish-oil supplements in heart disease. A wide range of mechanistic, epidemiologic, and controlled-trial evidence substantiates a role for omega-3 fatty-acid supplementation in both primary and secondary cardiovascular prevention. An extensive margin of safety has been confirmed in most settings. More work remains to be done in studying the effects of fish oil in specific subpopulations and circumstances as well as in clarifying optimal dosage regimens and EPA/DHA ratios. Only then can specific guidelines for administration of omega-3 supplements coalesce into consistent and clear recommendations from health-care professionals.

Dr. Hoffman is founder and medical director of the Hoffman Center in New York City. The author has no relationships to disclose relating to the content of this article.

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