Risk-benefit assessment of methylmercury and n-3 polyunsaturated fatty acids through fish intake by pregnant women in Shanghai, China: Findings from the Shanghai Diet and Health Survey.

Abstract

Fish and shellfish contain nutrients essential for fetal health, especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The concern of mercury (Hg) pollution limits fish consumption among women in pregnancy, which could adversely affect child development. This study aimed to conduct risk-benefit assessment and provide recommendations for fish intake by pregnant women in Shanghai, China. Secondary analysis was conducted using cross-sectional data from a representative sample of the Shanghai Diet and Health Survey (SDHS) (2016-2017), China. Dietary intakes of Hg and DHA+EPA were calculated from the food frequency questionnaire (FFQ) on fish items and 24hr recall record. Raw fish samples (59 common species of fish in Shanghai) were purchased in local markets and their concentrations of DHA, EPA and Hg were measured. Net IQ points gain was used to evaluate the health risk and benefit at a population level by FAO/WHO model. Recommended fish (i.e., high- DHA+EPA and low-level MeHg) were defined, and then the proportion of those hit 5.8 IQ points were simulated with their consumption frequency for 1, 2 and 3 times per week. The average consumption of fish and shellfish was 66.24g/d among pregnant women in Shanghai. The mean concentrations of Hg and EPA+DHA in fish species most commonly consumed in Shanghai were 0.179mg/kg and 0.374g/100g, respectively. Only 1.4% of the population exceeded the MeHg reference dose of 0.1μg/kg·bw/d, whereas 81.3% of those who did not meet the recommended daily intakes of 250mg EPA+DHA. In FAO/WHO model, the proportion of 28.4% reached the maximum IQ points gain. Along with the increase of "recommended fish" consumed, the simulated values of the proportion raised to 74.5, 87.3 and 91.9%, respectively. The pregnant women in Shanghai, China had an adequate fish consumption with low-level Hg exposure, but balancing the benefits of fish intake and risk of potential Hg exposure was still a challenge. It is necessary to define a local level of "recommended fish" consumption for developing dietary recommendations for pregnant women.