The 2014 FDA assessment of commercial fish: practical considerations for improved dietary guidance

In May 2014, the FDA released A Quantitative Assessment of the Net Effects on Fetal Neurodevelopment from Eating Commercial Fish (As Measured by IQ and also by Early Age Verbal Development in Children). The revised 2014 report builds on current data assessing fish consumption during pregnancy and provides a scientific basis for updated dietary advice. While the 2014 report addresses a specific subset of consumers, its findings are of general interest, especially since fetal development contributes to broad public health outcomes. Many fish species are a rich source of essential nutrients, such as protein, vitamin D, selenium, various minerals, and omega-3 fatty acids [1–4]; the nutritional benefits of fish, including the benefits for fetal cognitive development, are well established [4–6].

Despite evidence of nutritional benefit, American consumers have received seemingly contradictory advice about the nutritional value and methylmercury (MeHg) content of many fish species [7–10]. Furthermore, dietary decisions are also affected by a highly diverse market for fish with significant variability in price and geographic access [11–16].

To address the specific concerns, the FDA’s 2014 report dedicated separate analyses to the positive developmental effects of eating various fish and to the independent developmental effects of MeHg exposure, using both analyses to predict net cognitive outcomes for different patterns of fish consumptionInclusive of MeHg exposure, a consistent association was observed between maternal fish consumption and improvements in neurodevelopmental functioning in U.S. children through 9 years of age [17]. Subsequent modeling yielded estimates of the likely change in a child’s IQ due to the amount of a specific fish consumed during gestation. The curves tended to show a steep increase in predicted IQ, from slightly below average to moderately above average, when moving from low to recommended levels of fish consumption. Net cognitive benefits were consistently observed when consumption during pregnancy was more than 12 oz per week. Peak benefits varied for each type of fish but generally peaked at 1 to 3 meals per week, diminishing slightly at higher frequencies of consumption but maintaining overall cognitive benefit [17].

These data suggest that, for most fish species consumed in the US, recommended dietary levels do not cause significant MeHg exposure [17]. No adverse cognitive effects from MeHg are expected for most fish species when consumed at a level of 1 to 3 meals per week. Moreover, even at significantly higher levels of consumption than recommended, the negative effects of MeHg are predicted to be far smaller than the adverse effects of eating too little fish [17]. For example, about 120 light tuna sandwiches would need to be consumed each week before reaching the minimum MeHg exposure for adverse cognitive effects to be expected [17]. Lastly, there is a considerable difference between the recommended rate of fish consumption for maximum benefits during pregnancy (12 oz of various fish per week) reported in the current FDA advisory and the 2010 Dietary Guidelines for Americans and the amount currently eaten by pregnant women in the U.S. (1.89 oz per week) [17, 18].

Ideally, consuming the amount of seafood that offers peak benefit rates would lead to better cognitive development and health for many Americans. However, recent analyses on economic incentives and consumer attitudes have outlined challenges to adherence of dietary guidance, mainly attributed to concerns over cost and safety [11, 13, 20]. Consumers appear to overestimate risks of contaminant exposure and underestimate the risks of nutrient deficiency, an outcome with a greater likelihood of occurring [4, 21, 22]. Consumers of commercial fish have historically misinterpreted fish MeHg advisories and reduced their consumption of all fish as a “precaution” [4, 21, 23, 24]. This tendency has been vividly demonstrated in surveys and focus groups. Consumers surveyed in Belgium, for example, tended to have a higher awareness of contaminants in fish than of nutrients, and pregnant women in Boston showed a similar ignorance of nutritional benefits, while citing mercury contamination as a reason for avoiding fish altogether [3, 9].

Economic considerations also appear to limit fish intake. For instance, in opinion polling, fish consumption is influenced by the perception that fish are too expensive for routine consumption (Fig. 1) [25]. Though it is inaccurate for many fish species, this perception attests to the real economic forces that drive consumers toward inexpensive fish options.

Reasons for not eating the recommended amount of fish (aided), general population survey [25]. Survey participants were asked to check all that apply from four reasons provided to best describe why they do not eat the recommended amount of fish (at least 2 or 3 servings of any variety of fish or seafood each week)

FDA communications calibrated to emphasize nutritional benefits, appropriately present risk of MeHg exposure, and highlight the affordability of some fish products could have a major social impact and lead to improved dietary practices [4, 21, 26]. To that end, this review will supplement the FDA’s findings with econometric analyses, providing insight into the real-world determinants of dietary decision making and of fish consumption in particular. Below we survey the commercial fish species for which FDA data, pricing data, and regional access data are currently available. Our aim is to inform future advisories and educational initiatives by identifying the products likely to have the greatest value for public health, in terms of their combined nutritional benefits, affordability, and accessibility.