以往的研究认为吃含维生素A丰富的食品会降低肺癌、喉头癌、胃癌和食管癌的危险。研究人员对纽约西部178名男女食管癌病患者的研究中发现,食用松香油含量高食品要比食用松香油含量低的食品的人,癌症病例高达三倍以上。有些医学工作者密切观察从维生素A中选出胡罗卜素的保护作用.研究人员还发现:多食用含胡罗卜素的食品会降低患食管癌的危险。胡罗卜、西红柿、球花椰菜、菠菜和桃子等食品中含胡罗卜素丰富;而含高脂肪肉类、动物肝、黄油、全牛奶、蛋黄等食品中含有松香油(C_((?)2)H_(1(?)))。在纽约州大学的研究工作者们报告说“应更早地发现胡罗卜素与松香油对肺癌、口腔癌和喉头癌的不同影响.” Past research suggests that eating foods rich in vitamin A will reduce the risk of lung cancer, laryngeal cancer, stomach cancer and esophageal cancer. In a study of 178 men and women with esophageal cancer in western New York, the researchers found that people who consumed foods with high levels of rosin oil were more than three times more likely to suffer cancer than those who consumed foods with low levels of rosin oil. Some medical workers are closely monitoring the protective effect of carotenoids selected from vitamin A. Researchers also found that eating more foods that contain carotenoids reduces the risk of esophageal cancer. Carotene is abundant in foods such as carrot, tomato, ball cauliflower, spinach and peach, while rosin oil (C_ ()) is present in foods containing high fat meat, animal liver, butter, whole milk and egg yolk, 2) H_ (1 (?))). Researchers at the University of New York report that “the different effects of carotene and rosin oil on lung cancer, oral cancer and laryngeal cancer should be discovered earlier.”