单项选择题

You’ve probably heard some of the rules of the road when it comes to shopping healthfully at the grocery store: Don’t go shopping hungry because you’re likely to buy more than you need. Shop the perimeter (周边) of the store,where you’ll find the fresh stuff.
But perhaps the rule that is most perplexing is the one that asks shoppers to read the nutrition facts labels on products before buying them. Many people simply don’t understand what the label is saying if they bother to look at it.
Yet food experts say reading the label, and knowing what it says, is vitally important. Considering the label when you buy,say,a can of soup can help you make more healthful choices, says Mary DeBusman, a nutritionist with Alameda County Family Health Services.
The first portion of the label lists serving size and the number of servings in the container you’re buying. This is the first pitfall for shoppers who only look at the calories.
"Most people just zero in on the calories," she says. But a tiny pint of ice cream, for example, could have four servings with 280 calories per serving. If consumers see only the 280 calories and dig into the entire pint, they could be absorbing 1,120 calories in one sitting.
A section down from the calorie information is the nutrients portion of the label. The first line offers the total amount of fat in the food and what percentage it is of the amount of fat recommended in a 2,000 calorie daily diet. Buying products with lower percentage numbers,closer to 5 percent,is the best choice,the experts say.
Most Americans, the USDA says, don’t get enough dietary fiber, vitamin A, vitamin C, calcium and iron in their diets. That is why these are also important listings on the label. A good rule of thumb is that if the product has 5 percent of the daily value,that is low and 20 percent or more is high.
As far as the sweet stuff is concerned,the USDA suggests when comparing products you buy the one with the least amount of sugar. Many products, such as yogurt, have widely varying amounts of sugar in them.
DeBusman warns that all consumers should check the listed ingredients as well and avoid all products with hydrogenated oils,or trans fat. A product could have 0 grams of trans fat listed on the label if it has less than 0.5 grams total per serving. All amounts of trans fat should be avoided, she says. Look for "partially hydrogenated" oils on the ingredients list.
What do we learn from the last paragraph