巳知,在美国日光照射时间较少地区的直肠、大肠癌患者死亡率特别高。由此相反推理,可得以下假说:增加日光浴,使血液中的维生素D、钙结合蛋白、活性维生素D的水平上升,其结果必会导致直肠、大肠癌的发生率降低。或者说,饮食中的维生素D、钙的摄取 It is known that the mortality rate of patients with rectal and colorectal cancer is particularly high in areas with low sun exposure in the United States. On the other hand, the hypothesis is that the following hypothesis arises: Sunburn increases the levels of vitamin D, calcium-binding proteins, and active vitamin D in the blood. As a result, the incidence of rectal and colorectal cancers must be reduced. Or, dietary intake of vitamin D and calcium