Balancing the health benefits and risks from seafood consumption

It has become apparent that risk assessments for some chemical contaminants such as methylmercury must take into account the fact that the primary route of exposure, consumption of seafood, also involves the intake of beneficial nutrients. This represents a classic example of confounding, potentially biasing toward false negative inferences. Failure to consider the impact of nutrients will result in underestimation of the adverse effects of the contaminants, while failure to consider the impact of contaminants will result in underestimation of the beneficial effects of the nutrients. This has been demonstrated in three different prospective studies of methylmercury neurotoxicity conducted in the Faroe Islands, the Seychelles Islands, and Boston (Project Viva). The same principles have been demonstrated with respect to methylmercury and cardiovascular toxicity in Finland. It is also possible that some of this reflects biologic interaction, i.e., that seafood nutrients reduce the toxicity of contaminants and/or contaminants reduce the benefits of nutrients, although the evidence for this is weak at present. Balancing the benefits and risks is complicated by the fact that nutrient profiles (e.g., essential fatty acids) differ considerably among types of seafood, and that certain contaminants tend to be higher in certain types of seafood (e.g., lipophilic contaminants in fatty fish; methylmercury in muscle of long-lived predatory fish). These considerations reduce the usefulness of consumption advice that focuses solely on specific contaminants or nutrients and argue for a more integrated approach.