2012年下半年教师资格考试《英语学科知识与教学能力》（高级中学）真题试卷及答案解析

Passage 2

The first time I que8tioned the conventional wisdom on the nature of a healthy diet,I was in my salad days,almost 40 years ago,and the subject was salt. Researchers were claiming that salt supple mentation was unnecessary after strenuous exercise,and this advice was being passed on by health reporters. All I knew was that I had played high school football in suburban Maryland,sweating profusely

through double sessions in the swamplike 90-degree days of August. Without salt pills,l could't make it throu8h a two-hour practice;I couldn't walk across the parking lot afterward without cramping.

While sports nutritionists have since come around to recommend that we should indeed replenish salt when we sweat it out in physical activity,the message that we should avoid salt at all other times remains strong Salt consumption is said to raise blood pressure,cause hypertension and increase the risk of premature death. This is why the Department of Agriculture's dietary guidelines still consider

salt Public Enemy No. I ,coming before fats,su8;ars and alcohol. It's why the director of the Centers for 

Disease Control and Prevention has suggested that reducing salt consumption is as critical to 1ong-term health as quitting cigarettes.

And yet,this eat-less-salt argument has been surprisingly controversial-and difficult to defend

Not because the food industry opposes it,but because the actual evidence to support it has always been so weak.

When I spent the better part of a year researching the state of the salt science back in 1998-al—ready a quarter century into the eat-less-salt recommendations-journal editors and public health administrators were still remarkably candid in their assessment of how flimsy the evidence was implicating salt as the cause of hypertension.

While,back then,the evidence merely failed to demonstrate that salt was harmful,tbe evidence from studies publishes over the past two years actually suggests that restricting how much salt we eat can increase our likelihood of dying prematurely. Put simply,the possibility has been raised that if we were to eat as little salt as the U. S. D. A. and the C. D. C. recommend,we'd be harming rather than helping ourselves.

Why have we been told that salt is so deadly? Well,the advice has always sounded reasonable. It has what nutritionists like to call " biological plausibility. " Eat more salt and your body retains water to maintain a stable concentration of sodium in your blood. This is why eating salty food tends to make us thirsty:we drink more;we retain water. The result can be a temporary increase in blood pressur,

which will persist until our kidneys eliminate hoth salt and water.

The scientific question is whether this temporary phenomenon translates to chronic problems: if we eat too much salt for years,does it raise our blood pressure,cause hypertension,then strokes,and then kill us prematurely:l  It makes sense,but it's only a hypothesis. The reason scientists do experiments is to find out if hypotheses are true.

The N. I. H.  has spent enormous sums of money on studies to test the hypothesis,and those studies have singularly failed to make the evidence any more conclusive.

With nearly everyone focused on the supposed benefits of salt restriction,little research was done

to look at the potential dangers. But four years ago,ltalian researchers began publishing the results from a series of clinical trials,all of which reported that,among patients with heart failure,reducing salt consumption increased the risk of death.