不要怕晒太阳！维生素D可以预防结肠癌

The sun you get when you mow the lawn or run errands could protect you against colon cancer, new research shows.

新研究显示，你在修剪草坪或跑腿时得到的阳光，可以保护你免受结肠癌的侵袭。

How? Sunlight prompts the production of vitamin D, and people with sufficient levels of the vitamin had a 22 percent lower risk of colon cancer, said lead researcher Marjorie McCullough. She’s senior scientific director of epidemiology research for the American Cancer Society.

它是怎么做到的？首席研究员马乔里·麦卡洛说，阳光促进了维生素D的产生，维生素含量足够的人患结肠癌的风险降低了22 %。她是美国癌症协会流行病学研究的高级科学主任。

That risk also appears to decrease further as vitamin D levels rise, though the study did not prove that sunlight causes colon cancer risk to drop.

随着维生素D水平的升高，这种风险似乎也进一步降低，尽管这项研究没有证明阳光会降低结肠癌的风险。

The chances of developing colon cancer decline about 19 percent in women and 7 percent in men for every incremental increase in blood vitamin D levels, the researchers found.

研究人员发现，每增加一次血液维生素D水平，女性患结肠癌的几率就会下降19 %，男性下降7 %。

"It appeared across most of the range we were looking at, the relationship was linear," McCullough said.

麦卡洛表示，“在我们观察的大部分范围内，这种关系都是线性的。”

Colon cancer is the third most common cancer and the third leading cause of cancer-related deaths in both men and women in the United States, with about 140,250 new cases and 50,630 deaths expected during 2018, the researchers said in background notes.

研究人员在背景资料中说，结肠癌是美国第三大最常见的癌症，也是导致男性和女性癌症相关死亡的第三大原因，预计2018年将有140，250例新病例和50，630例死亡。

About 1 in every 24 women and 1 in every 22 men will develop colon cancer during their lifetime, they said.

他们说，大约每24个女性中就有1个，每22个男性中就有1个会在一生中患上结肠癌。

"It has long been postulated that vitamin D deficiency can cause other problems besides osteoporosis and immune system dysfunction," said Dr. Len Horovitz, an internist with Lenox Hill Hospital in New York City who was not involved with the study.

“长期以来，人们一直认为维生素D缺乏会导致骨质疏松症和免疫系统功能紊乱之外的其他问题，”纽约Lenox Hill医院的内科医生伦霍洛维茨博士说，他没有参与这项研究。

"The suspicion that vitamin D deficiency might be responsible for the development of cancer is corroborated in this study, where vitamin D deficiency and colorectal cancer are linked," Horovitz said.

霍洛维茨说:“这项研究证实了维生素D缺乏可能导致癌症的发生，维生素D缺乏与结直肠癌有关联。”。

Don’t start baking yourself to avoid colon cancer, however.

但是，也不要为了避免患结肠癌而去太阳下烧烤哦。

Only about 7 percent of the U.S. population have levels of vitamin D deficiency low enough to increase their risk of colon cancer, McCullough said.

麦卡洛说，只有大约7 %的美国人因为维生素D太少而增加了患结肠癌的风险。

"If you live in a sunny area year-round, or if you’re living in an area where the spring and summer months are warmer, your levels will be higher just incidentally," McCullough said. "We do not recommend people seek sun exposure to raise their vitamin D levels, because UV radiation is a strong risk factor for skin cancer."

麦卡洛说:“如果你一年四季都住在阳光明媚的地方，或者你住在春夏两个月都比较温暖的地方，你体内的维生素D水平自然就会更高。我们不建议人们寻求阳光照射来提高他们的维生素D水平，因为紫外线辐射是皮肤癌的一个很强的危险因素。”

Vitamin D has long been associated with bone health, but the nutrient hasn’t been recommended to protect against colon cancer or other health problems due to scant research, McCullough said.

麦卡洛说，维生素D长期以来与骨骼健康相关，但由于研究一直不多，维生素D并未被推荐用于预防结肠癌或其他健康问题。

When the U.S. National Academy of Medicine put out its vitamin D guidelines in 2011, it concluded that the medical evidence of vitamin D benefits for cancer were not sufficient enough to make a recommendation, she said.

她说，当美国国家医学研究院在2011年发布维生素D指南时，它得出的结论是，维生素D对癌症有益的医学证据不足以提出建议。

To clear this up, McCullough and her colleagues combined data from 17 different studies involving 5,706 people with colon cancer and 7,107 healthy participants from the United States, Europe and Asia.

为了澄清这一点，麦卡洛和她的同事将来自17项不同研究的数据结合起来，这些研究涉及5，706名结肠癌患者和7，107名来自美国、欧洲和亚洲的健康参与者。

The researchers even reanalyzed blood samples from about a third of the participants, so they could perform a more direct apples-to-apples comparison across all of the 17 studies.

研究人员甚至重新分析了大约三分之一的参与者的血样，这样他们就可以在所有17项研究中进行更直接的比较。

They concluded that vitamin D does indeed appear to provide protection against colon cancer, particularly for women.

他们的结论是，维生素D确实能预防结肠癌，尤其是对女性。

Most people get enough vitamin D just by living their lives, McCullough said.

麦卡洛说，大多数人在日常生活中就能获得足够的维生素D。

The sunlight you get from a casual walk down the street, running errands and even walking from the car or train to your office building is sufficient to stimulate proper vitamin D production in your body, she said.

她说，你在街上随意散步、跑腿，甚至从汽车里或者下火车后步行到办公大楼时晒到的阳光足以刺激你体内适当的维生素D产生。

People also get vitamin D from fortified foods like milk, cereal and orange juice, and from fatty fish like salmon, tuna, trout and swordfish, McCullough said.

麦卡洛说，人们还可以从牛奶、谷类食品和橙汁等强化食品中获取维生素D，也可以从鲑鱼、金枪鱼、鳟鱼和剑鱼等肥胖的鱼类中获取维生素D。

Because of this, people shouldn’t rely on supplements to get their vitamin D, McCullough said. Heavy doses of vitamin D can be toxic.

正因为这些，人们不应该依靠补充剂来获得维生素D，麦卡洛说。大剂量的维生素D可能有毒。

"High-dose individual supplements are not recommended," she said.

“不建议使用大剂量的个人补充剂，”她说。

It’s not known exactly why vitamin D could protect against cancer, but researchers suspect the vitamin plays a role in controlling cell growth and promoting programmed cell death, McCullough said.

麦卡洛说，目前还不清楚为什么维生素D能预防癌症，但研究人员怀疑维生素在控制细胞生长和促进程序性细胞死亡方面起著作用。

"Cancer occurs when there’s uncontrolled growth and spread of abnormal cells," she said. "Experimental studies have shown that vitamin D can help to limit proliferation of abnormal cells."

“当异常细胞不受控制地生长和扩散时，癌症就会发生，”她说。实验研究表明，维生素D有助于限制异常细胞的增殖。"

The new study was published June 14 in the Journal of the National Cancer Institute.

这项新研究于6月14日发表在国家癌症研究所的期刊上。