Fish consumption has been shown to be inversely associated with CHD, which may be due to n-3 fatty acids. The n-3 fatty acids, EPA and DHA, are naturally found only in marine sources. Dietary intakes of methylmercury from certain fish have been hypothesized to increase the risk of CHD.

To investigate the relationship between 30 d fish frequency consumption (assessed by FFQ), total blood Hg concentrations and risk markers of CHD in women aged 16-49 years participating in the National Health and Nutrition Examination Survey 1999-2002.

Multiple linear regression analyses were used to test (i) the relationships between 30 d fish frequency consumption and five CHD risk markers, i.e. HDL cholesterol (HDL-C), LDL cholesterol, total cholesterol, TAG and C-reactive protein (CRP); and (ii) if total blood Hg attenuated any associations between fish consumption and CHD risk markers in non-pregnant, non-diabetic females aged 16-49 years.

Total 30 d fish frequency consumption was negatively associated with CRP (b = -0.10, 95 % CI -0.19, -0.02, P = 0.015) and positively associated with HDL-C (b = 1.40, 95 % CI 0.31, 2.50, P = 0.014). Adjustment for other risk factors did not significantly attenuate the associations. Despite the collinearity between fish and Hg, there is a protective association between fish intake and CHD risk factors.

The levels of DHA + EPA and other nutrients in fish may be adequate to offset the hypothesized risks of heart disease related to ingesting Hg from fish.