維生素D爲何能對抗結腸癌

Higher levels of vitamin D have been associated with a reduced risk of colon cancer in many observational studies. A new analysis has found a possible reason.
很多觀察性研究發現，血液中維生素D含量越高，患結腸癌的風險越低。一項新研究可能找到了其中一個原因。

A malignant tumor contains not just cancer cells but many types of cells, some of which affect how fast a tumor may grow or spread. Among them are a group of immune system cells called T lymphocytes, or T cells, that can target tumor cells and limit their growth. Having a tumor with more T cells correlates with a better prognosis.
惡性腫瘤中不僅有癌細胞，還有很多其他種類的細胞，其中一些細胞能影響腫瘤變大或擴散的速度。其中有一羣免疫系統細胞，名叫T淋巴細胞或T細胞，它們能攻擊腫瘤細胞，限制它們的發展。含有更多T細胞的腫瘤，預後情況更好。

The study, published in the journal Gut, included 318 people who had developed colorectal cancer and 624 matched controls. All had vitamin D levels measured before the appearance of any cancers.
這項發表在《內臟》(Gut)雜誌上的研究調查了318名結直腸癌患者和624名匹配的對照組人員。研究人員測量了所有這些人出現任何癌症之前的維生素D水平。

The higher the blood levels of vitamin D, the less likely people were to develop colorectal tumors. Vitamin D, the authors suggest, interacts with the immune system to prevent the growth of this type of malignancy.
血液中的維生素D含量越高，越不可能患上結直腸腫瘤。這項研究的作者們認爲，維生素D與免疫系統相互作用，能預防這類惡性腫瘤的生長。

“This study really shows that vitamin D has an effect on immunity,” said the senior author, Dr. Shuji Ogino, an associate professor of pathology at the Dana-Farber Cancer Institute in Boston, “and it’s the first study to show that in a human population. Vitamin D boosts immunity not just in cancer, but in fighting infections as well.”
這項研究的資深作者、波士頓丹娜法伯癌症研究院(Dana-Farber Cancer Institute)的病理學副教授荻野修二(Shuji Ogino)說，“這項研究確實表明，維生素D能提高免疫力。它是第一項在人體上表明這一點的研究。維生素D對免疫力的促進作用不僅在於防癌，還在於對抗感染。”