A、Salt is quite necessary for the health of humans. B、Eating too much salt could do harm to the heart. C、The quantity of salt va

(20)We reported about a study that showed eating even a little less salt could greatly help the heart. The study was published in the New England Journal of Medicine. The scientists used a computer model to predict how just three grams less salt a day would affect heart disease in the United States. The scientists said the results would be 13% fewer heart attacks, 8% fewer strokes, 4% fewer deaths and 11% fewer new cases of heart disease. They and public health professionals in the United States are interested in a national campaign to persuade people to eat less salt. However, some scientists say such a campaign is an experiment with the health of millions of people. Michael is among the critics. He is a high blood pressure expert.(21)He says that eating less salt results in lower blood pressure. But he says studies have not clearly shown that lowering salt means fewer heart attacks or strokes. And he says salt has other biological effects. He says calling for reductions in the national diet could have good effects, but it could also have harmful results and there is not enough evidence either way. Another critic is David, a nutrition and kidney disease expert. He and his team looked at large studies of diets in 33 countries.(22)They found that most people around the world eat about the same amount of salt. Most of them eat more salt than American health officials advise. David says the worldwide similarity suggests that a person’s brain might decide how much salt to eat.
20. What can we learn from the study?
21. What does high blood pressure expert Michael imply?
22. What does nutrition expert David find?