_in britain, for example, people thought it would make them sick because it looked like a harmful plant. in addition, it sometimes caused lead poisoning among the rich, as they ate the acidic tomatoes on expensive plates made of materials containing lead. poor people, however, did not have this problem since they used cheap plates made of wood. therefore, tomatoes were only eaten by poor people until the 19th century.
this changed after many italians moved to america during the 19th and 20th centuries.
they brought with them dishesmade with tomatoes, such as pizza and spaghetti, which many people enjoyed. this helpedspread the tomato’s popularity to other cultureswhich the italians came into contact with in america, and eventually to the world.

고 1 능률찬 지문내용 중 일부입니다...

밑줄 친 부분 해석이 잘 안되요.... 그리고 them 뒤에 혹시 생략되어 있는 단어가 있나요 ?????
그리고 they와 them이 각각 가리키는 것이 무엇인지 친절한 답변 부탁드립니다..