A small piece of fish each day may keep the heart doctor away. That's the finding of a study of Dutch men in which deaths from heart disease were more than 50 percent lower among those who consumed  at least an ounce of salt water fish per day compared to those who never ate fish. The Dutch research is one of three human studies that give strong scientific support to the long held belief that eating fish can provide health benefits, particularly to the heart. Heart disease is the number-one killer in the United States, with more than 550,000deaths occurring from heart attacks each year. But previous research has shown that the level of heart disease is lower in cultures that consume more fish than Americans do. There are fewer heart disease deaths, for example, among the Eskimos of Greenland, who consume about 14 ounces of fish a day, and among the Japanese, whose daily fish consumption averages more than 3 ounces. For 20 years, the Dutch study followed 852 middle-aged men, 20 percent of whom ate no fish. At the start of the study, average fish consumption was about two-thirds of an ounce each day, with more men eating lean fish than fatty fish. During the next two decades, 78of the men died from heart disease , The fewest deaths were among the group who regularly ate fish, even at levels far lower than those of the Japanese of Eskimos, This _ was true regardless of other factors such as age, high blood pressure, or blood cholesterol levels. The passage is mainly about  _  .
the changes in people's diet the daily fish consumption of people in different cultures. the high death rate of disease in some countries. the effect of fish eating on people's health