Once considered a fringe(非主流的)food by the U.S. culinary mainstream, sweet potatoes are
fast becoming popular everywhere from fast food chains to expensive restaurants and the White
House table.
    Three years ago, the "Wall Street Journal" wrote in a front page article that except for their use in
a Thanksgiving dish, sweet potatoes were a wholly uninteresting food. Yet over the past two years,
the number of restaurants offering a sweet potato-based side dish has increased 40 percent. Food
giant ConAgra just spent $155 million to open the world's first plant devoted entirely to frozen sweet
potato products, and U.S. farmers are planning to harvest a record-setting 2 billion pound crop.
    "It's not something we believe is a fashion,"said Andy Johnston of ConAgra Foods Lamb Weston.
    According to research conducted by ConAgra, 30 percent of sweet potato eaters report consuming
the vegetable several times per month. Only 12 percent eat them only during the Thanksgiving and
winter holiday season.
    Analysts attribute the sweet potato's growing popularity in large part is due to sweet potato fries,
which account for the majority of the vegetable's presence in U.S. restaurants. In fact, Google searches
for "sweet potato fries" increased 40 percent over the past year.
    Sweet potatoes have also become popular among more conscious eaters, however, in part because
they are high in vitamins and have a low glycemic (血糖的) index in spite of their sweetness. Both
Weight Watchers and the South Beach Diet have recommended sweet potatoes, roasted in a little oil
rather than fried, and doctors are recommending them for diabetics.
   "Within the diabetic community, it's become pretty common knowledge that sweet potatoes are good
for you, so there's a great appeal because so many people have diabetes now,"said Chef Michel Nischan, who helps host a TV show for people with diabetes.