Clinical Question: Does the type of fish and its preparation affect the degree of cardiovascular benefit?

Setting: Population-based

Study Design: Cohort (prospective)

Synopsis: Investigators identified 5,201 men and women older than 65 years from four U.S. communities between 1989 and 1990. Patients with known ischemic heart disease at baseline were excluded from the trial, as were those who failed to complete the dietary survey, leaving 3,910 persons in the final study population. Subjects were asked how often they ate each of the following: fried fish or fried fish sandwich (fish burger); tuna fish/tuna salad/tuna casserole; and other fish (broiled or baked). The range was less than five times per year to five or more times per week.

The levels of n-3 polyunsaturated fatty acid were increased in a sample of patients eating tuna or other fish, but not in those eating fish burgers. The mean duration of follow-up was 9.3 years, with annual in-person examinations and interim telephone calls at six months. The investigators used these visits plus medical records and administrative databases to determine the outcomes. The percentage of patients lost to follow-up was not evident, although it appears to be less than 20 percent. Because consumption of tuna and other fish was correlated, these groups were combined.

Participants consumed 0.7 servings per week of fish burgers and 2.2 servings per week of tuna or other broiled or baked fish. After adjusting for potential confounders, consumption of tuna or other fish was associated with a lower risk of death from ischemic heart disease and fatal arrhythmia, although it had no effect on the risk of nonfatal myocardial infarction. Fish burgers were associated with nonsignificant trends toward greater risk. Based on the unadjusted figures, persons eating tuna or other fish less than once a month had 39 ischemic deaths in 3,324 person-years, compared with 39 deaths in 11,593 person-years for those eating tuna or other fish at least three times a week. That corresponds to 119 patient-years of eating tuna or other broiled or baked fish three or more times a week instead of less than once a month to prevent one death from ischemic heart disease.

Bottom Line:We should encourage patients to avoid eating the drive-through fish burger and instead have a tuna fish sandwich (light on the mayonnaise) or broiled salmon. (Level of Evidence: 2b)