据哈佛大学口腔系的研究,从蔬菜中提取的维生素A的前驱物质β-胡萝卜素显示出具有某些抗肿瘤的特性。美国自1982年开始,由国立癌症研究所投资,有2万2千名医师参加,通过临床试验研究了β-胡萝卜素的防癌效果。其将实验动物分为4组,2组每日投用β-胡萝卜素30mg, According to Harvard University’s Department of Stomatology, beta-carotene, a precursor of vitamin A extracted from vegetables, shows some anti-tumor properties. Since 1982, the United States has invested in the National Cancer Institute and has participated in 22,000 doctors. Clinical trials have examined the anti-cancer effects of beta-carotene. The experimental animals were divided into 4 groups, and 2 groups were given β-carotene 30 mg daily.