acid (EPA) and docosahexaenoic acid (DHA), two long-chain w-3 polyunsaturated fatty acids (PUFAs) found in many fish. They also reviewed studies of neurological and cancer risk increases associated with intake of the methylmercury, polychlorinated biphenyls and dioxins found in some fish. Large prospective studies and randomised trials were included in the analysis, but the article does not make clear the precise number of studies.

Each 100 mg of EPA and DHA intake daily was associated with a 15% reduction in the relative risk for death from coronary heart disease. The CHD mortality benefit leveled off at 36% for an intake level of 250 mg per day (one to two fish servings per week), contributing to a 17% reduction in all cause mortality risk. These benefits of w-3 PUFAs dwarfed the overall neurological and cancer risk increases associated with fish-related intake of chemical contaminants.

Comment: According to this analysis, fish intake provides substantial cardiovascular benefits, even at a level below the currently recommended DHA and EPA intake target of 1000 mg per day. The authors recommend a weekly target of 1500 to 2000 mg, about the amount in one 170 g serving of oily fish such as salmon; for fish with less w-3 PUFA content, more servings would be needed. However, children aged 12 years or younger and women who are or may become pregnant should limit their intake to avoid possible mercury exposure. A recent US Institute of Medicine report specifically calls two 85 g servings of fish per week a `reasonable' intake level for these vulnerable groups, and recommends that they eat no more than 170 g per week of albacore tuna and simply avoid eating large predatory fish such as shark or swordfish. JoAnne M. Foody

Reference: Mozaffarian D, Rimm EB. Fish intake, contaminants, and human health: evaluating the risks and the benefits. JAMA 2006; 296:1885-1889.