挪威一个群体研究显示维生素 A 摄取量的一个指数与肺癌发生率呈负相关。其他研究也显示类似结果。随着发现β-胡萝卜素而非已转化成维生素 A 与肺癌发生率呈负相关,以及认识到β-胡萝卜素如何对肺癌起到预防作用,人们转而重视β-胡萝卜素。 A Norwegian population study showed that an index of vitamin A intake was negatively correlated with the incidence of lung cancer. Other studies have also shown similar results. With the discovery that β-carotene, but not vitamin A, has been negatively correlated with the incidence of lung cancer, and that how β-carotene can prevent lung cancer, people are turning to β-carotene.