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Seafood Consumption, Mercury Exposure, and Mortality
Quick Takes
- In a large modern cohort, there was no association with mercury exposure and related mercury blood levels associated with seafood consumption and all-cause and CVD mortality.
- Seafood is an excellent source of protein and omega-3 PUFAs with very little saturated fat. That seafood intake in the population that was isocaloric by quartiles of mercury levels, which would be associated with lower saturated fat intake and provide micronutrients was associated with much higher EPA/DHA intake and higher mercury levels (primarily methylmercury), suggest there may be confounders limiting or underestimating the protective effect of seafood.
Study Questions:
Is there an association of seafood consumption and mercury exposure with all-cause and cardiovascular disease (CVD)–related mortality in the US general population?
Methods:
A prospective cohort study included adults aged ≥20 years who participated in the 2003–2012 cycles of the National Health and Nutrition Examination Survey (NHANES); data were linked to mortality records through December 31, 2015. Data analysis was performed from January–March 10, 2021. Seafood consumption was assessed through two 24-hour dietary recalls, and mercury exposure was assessed by blood mercury levels. Standard NHANES data on lifestyle; at-risk behavior; socioeconomic, laboratory, and physical metrics; and nutrition were obtained at several intervals. The primary outcome was all-cause and CVD-related mortality. Multivariable Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of mortality associated with usual seafood consumption and blood mercury concentration quartiles.
Results:
The study included 17,294 participants (mean [SD] age, 45.9 [17.1] years; 9,217 [53.3%] female) with a mean (SD) blood mercury concentration of 1.62 (2.46) μg/L. During 2003–2016, mean (SE) blood mercury concentrations remained generally unchanged. Blood mercury concentrations correlated weakly with fish consumption (r = 0.23, p < 0.001). During 131,276 person-years of follow-up, 1,076 deaths occurred, including 181 deaths from CVD. The multivariable-adjusted HR for an increase in seafood consumption of 1 ounce equivalent per day and all-cause mortality was 0.84 (95% CI, 0.66-1.07) and for CVD-related mortality was 0.89 (95% CI, 0.54-1.47). Blood mercury level was not associated with all-cause or CVD-related mortality. Comparing the highest with the lowest quartile of blood mercury concentration, the multivariable-adjusted HRs were 0.82 (95% CI, 0.66-1.05) for all-cause mortality and 0.90 (95% CI, 0.53-1.52) for CVD-related mortality.
Conclusions:
In this cohort study of US adults, seafood consumption and mercury exposure with the current seafood consumption level were not significantly associated with a risk of all-cause or CVD-related mortality. These findings may inform future public health guidelines regarding mercury exposure, seafood consumption, and CV health promotion.
Perspective:
The mean level of mercury in the blood of persons with moderate to high levels of exposure is 10.0 µg/L, while low to moderate exposure is associated with a median level of 1.40 µg/L; similar to the study cohort. Although disappointing that seafood was not associated with a decrease in all-cause and CV mortality, this is a very important study for those who love lobster, shrimp, cold water fish, and other seafood—they are very low in saturated fat, high in omega-3 polyunsaturated fatty acids (PUFAs) which have many benefits, and excellent sources of protein. There are 84 calories and 18 grams of lean protein in seven medium-sized pieces of shrimp. That’s nearly 50% of the daily recommended serving of protein for only 10% of the day’s needed calories. The cholesterol content in shrimp has little effect. But dipping lobster or shrimp in butter is not a good idea. One tablespoon of butter has 104 calories of fat and over 7 grams of saturated fat.
Clinical Topics: Cardiovascular Care Team, Dyslipidemia, Prevention, Lipid Metabolism, Nonstatins, Diet
Keywords: Cardiovascular Diseases, Cholesterol, Diet, Fatty Acids, Fatty Acids, Omega-3, Health Promotion, Life Style, Mercury, Methylmercury Compounds, Primary Prevention, Public Health, Seafood, Socioeconomic Factors
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