Passage 1

People who do not get enough vitamin A in their food may develop night blindness. But in the developing countries, especially the countries in Africa, a lack of vitamin A causes much more serious harm to children. The World Health Organization reports that the lack of vitamin A leads to as many as two hundred fifty thousand child deaths every year.

Sweet potatoes with orange flesh have high levels of vitamin A. Experts say

orange sweet potatoes could help solve the lack of vitamin A in Africa. But, first, more people there will need to be persuaded to eat them. Jan Low with the International Potato Center, a research organization, says the sweet potato needs a better image in Africa. She said, “We do have an image problem with sweet potato in general in Africa. Most of the local people refuse to grow sweet potatoes. It is seen as a food of the poor.” Ms. Low explains that sweet potatoes are mainly grown by poor women to feed their families in case other crops fail.

The sweet potatoes commonly grown in Africa have white or yellow flesh. But,more importantly, they are low in vitamin A. Thus, Jan Low and her partners managed to tell the African people that orange sweet potatoes had high levels of vitamin A. They made use of the radio to spread the message that orange sweet potato is good to human health. They said that orange sweet potatoes were able to help you fight diseases, make you strong, clear your skin and make you look healthy.

In areas without radio, they spread the message through singing, dancing and storytelling in local theaters. And everywhere they went, they wore orange T-shirts and hats. They even drove orange vehicles. Jan Low says the color of the tuber (植物的块茎) made it easier to gain public attention.

Dan Gustafson works for the United Nations Food and Agriculture Organization. He pays attention to efforts in the past to increase the popularity of other nutritious crops. He says most of these efforts failed because organizers did not consider what people wanted to eat. But Mr. Gustafson sees a better chance for the efforts to increase the popularity of the orange sweet potato in Africa. For one thing, except for the color, the orange sweet potato is similar to what people already use. He is confident about the popularity of orange sweet potato in Africa and the improvement of people’s health condition there.

 There is an image problem with sweet potatoes in Africa because ____.