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尽管维生素A及其衍生物在实验性致癌中可能起重要作用,但是,关于维生素A和人癌肿之间的关系尚不清楚。对饮食习惯和癌肿发生率以及癌肿病人血清视黄醇水平的研究,获得的大量证据支持这种关系存在。早期研究提示,血清视黄醇水平降低可能增加癌肿发生的危险性.然而,近期研究确不能证实血清视黄醇水平和癌肿总发生率之间的负相关系。肿瘤患者血清视黄醇水平减少,可为原发性,也可为继发性。例如,血清视黄醇水平降低可能是维生
Although vitamin A and its derivatives may play an important role in experimental carcinogenesis, the relationship between vitamin A and human cancer is unclear. The study of dietary habits, cancer incidence, and serum retinol levels in cancer patients has yielded substantial evidence supporting this relationship. Early studies suggest that decreased serum retinol levels may increase the risk of cancer occurrence. However, recent studies have failed to confirm the negative relationship between serum retinol levels and the overall incidence of cancer. Serum retinol levels in patients with cancer may be primary or secondary. For example, a decrease in serum retinol levels may be a survival