Omega-3 fatty acids belong to a group of compounds known as polyunsaturated fats. These fats serve as the raw material for a whole host of essential structures in the body, from brain cells to molecules (分子) that regulate blood pressure.

Since our bodies cannot manufacture their own supply of omega-3s, we have to get them from the food we eat, mostly from fish but also from plant sources like soybeans (大豆).

The American Heart Association has recommended that everyone eat two 85-g servings of fatty fish a week. But the A.H.A’s expert panel wasn’t ready to declare that taking omega-3 pills will protect your heart. It’s just too easy to get more omega-3 than you need from pills, and the panel was worried that an excess could cause serious side effects, such as internal bleeding.

The U.S. Food and Drug Administration, however, allowed manufactures of omega-3 pills and fish oils to advertise the fat’s benefits—as long as the label does not suggest taking more than two grams per day.

One thing is clear whether you get your omega-3s from pills, oils or fish: they are not cure-alls. You still have to eat a well-balanced diet that’s lower in total fat than most Americans currently consume. Otherwise, you’re fishing for trouble.

26. Doctors have long been puzzled by       .

      A. why red meat is harmful      B. how beneficial fish are

      C. what makes fish healthful      D. how red meat is replaced

27. We can learn from the passage that       .

1. A.      human beings get omega-3s from their food
2. B.      omega-3s are only found in fish and soybeans
3. C.      omega-3s are the raw material for saturated fats
4. D.     polyunsaturated fats constitute human molecules

28. The A.H.A. didn’t recommend omega-3 pills, because       

1. A.      it had no knowledge of the safe dose of omega-3
2. B.      it had no evidence that they can protect the heart
3. C.      the pills contain too little omega-3 to be helpful
4. D.     one is likely to get too much omega-3 from the pills

29. The FDA allowed manufacturers of omega-3 pills and fish oils to advertise omega-3’s benefits on condition that       

1. A.      their suggested dose is printed on the label
2. B.      their suggested dose is within the safety limit
3. C.      the fat’s potential side effects are mentioned
4. D.     the products contain side effects are mentioned

30. The writer seems to suggest that       

1. A.      omega-3s can balance one’s diet
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