When you start to consider contamination from mercury and PCBs (Polychlorinated biphenyl, or industrial chemicals), picking the best fish gets a little more confusing. Organizations such as the Food and Drug Administration (FDA), Institute of Medicine (IOM), Food and Agriculture Organization of the United Nations (FAO), and the World Health Organization (WHO) have tried to weigh the contamination risk of eating fish against the nutritional benefits it provides. The EPA and FDA have established guidelines for pregnant women, women trying to conceive, nursing mothers and young children. For other adults, the general advice is to basically ''eat fish.'' Based on research, these groups feel that the health benefits of eating fish far outweigh any risk from contaminants. While it may be possible that a fish could be so high in contaminants and low in omega-3 fatty acids that it could do you more harm than good, no such fish has been found to date that fits this description. The advice from these organizations is to eat two or more servings of fish weekly from a variety of species, therefore reaping the nutritional benefits and lessening the risk of over-exposure to the same contaminant in the same species repeatedly.
On the other end of the spectrum is the Environmental Defense Fund (EDF). This group has a published guide that lists 20 species of fish from which adults should consume no more than once serving per month. When formulating their list, the EDF only considers risk—how much contaminant is present—not whether the listed fish may have any health benefit that could outweigh the contamination risk. Both the EPA and FDA are concerned about the overstating of risk by the EDF, when using a risk-only method to compare fish. They have therefore set up an advisory for fish consumption for all US states based on available species.
Experts on both sides of the discussion agree that, in theory, it is possible to get excessive mercury contamination by eating a large quantity of high-mercury fish---but they don’t agree on how much is too much. However, the amount of fish that would need to be consumed is far more than the 3 oz. of fish per week that Americans are currently eating, on average.
For people concerned with mercury contents of fish, refer to the guide below. Mercury concentration is listed as Parts Per Million (PPM):
Finally, there is the concern of depleting the waters of fish and using ecologically damaging methods of fishing and fish farming. Sustainable fishing practices are critical to preventing the extinction of fish species. Advocacy groups, grocery stores, and consumers are trying to help reverse trends of overfishing so that the industry as a whole can move toward greater sustainability. Environmental concerns are different from region to region in the United States and throughout the world. Concerns can also change seasonally as well. For the most up-to-date information on selecting fish with the least environmental burden, please check out the sustainability of your fish choices using this listing by the Monterey Bay Aquarium