The study deals with the intake(摄影) of n-3 fatty acids and fish. The researchers calculated the intake of fish for 44,895 male health professionals—most of them dentists—in 1986 and kept track of their health status for the next six years. Surprisingly, the intake of n-3 fatty acids or fish in 1986 was not related to the risk of subsequent coronary disease. The number of participants was much larger than in other studies, and the methods and data analysis were solid. Also, measurements of fatty acids in adipose tissue showed that the questionnaire reliably ranked respondents according to their intake of 3 fatty acids.
The researchers carefully spell out the limitations of the study. First, two thirds of the men had greatly increased their intake of fish over the 10 years before 1986. Some of those increases could have occurred. Shortly before the base-line investigation in 1986, because the inverse relation between fish consumption and mortality due to coronary heart disease was first reported in 1985. Thus, data on fish intake may not reflect long term habits, and changes in fish intake during follow-up could also have attenuated an association with coronary disease. The authors performed separate analyses including only men who reported no change in their fish intake and again found no effect. However, it is hard for people to recall whether they changed their diet several years ago.
Second, the fish intake of these educated men was high and was more comparable with that of Norwegians or Japanese than with intake in the U.S. men studied previously. The epidemiologic data suggest that any beneficial effect is obtained with one or two servings of fish per week and that more is not better. Moreover, previous studies of fish intake have shown an association with the rate of mortality due to coronary disease, rather than with the incidence of nonfatal coronaty disease or coronary surgery. When seen in that light, there is some agreement between the present study and previous reports, because the risk of death from coronariy heart disease was about 25 percent lower among men who ate at least some fish than among those who ate no fish at all.
A third limitation of the study was that some of the men studied may have begun to eat fish, or may have eaten more, because they thought that they were at increased risk of a heart attack;the men in the highest 20 percent of the study group in terms of their in-take of n-3 fatty acids more frequently reported a family history of coronary disease or a personal history of high cholesterol levels than men who ate less fish.
The Harvard investigators concluded that increasing fish intake beyond one or two servings per week is unlikely to reduce the risk of coronary events substantially in men who are initially free of coronary disease. This is a prudent conclusion, and it could be extended to fish-oil capsules, which provide n-3 fatty acids in much larger amounts than are commonly consumed in food.
The findings of the Health Professionals Follow-up Study should somewhat dampen enthusiasm for fish and fish oil as a panacea against coronary disease. A little fish may still do some good, but more fish is not necessarily better.
Good diet helps prevent coronary heart disease.

A. Right
B. Wrong
C. Not mentioned