不要怕曬太陽！維生素D可以預防結腸癌

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

新研究顯示，你在修剪草坪或跑腿時得到的陽光，可以保護你免受結腸癌的侵襲。

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?首席研究員馬喬里·麥卡洛說，陽光促進了維生素D的產生，維生素含量足夠的人患結腸癌的風險降低了22 %。她是美國癌癥協會流行病學研究的高級科學主任。

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.

隨著維生素D水平的升高，這種風險似乎也進一步降低，盡管這項研究沒有證明陽光會降低結腸癌的風險。

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.

研究人員發(fā)現，每增加一次血液維生素D水平，女性患結腸癌的幾率就會下降19 %，男性下降7 %。

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

麥卡洛表示，“在我們觀察的大部分范圍內，這種關系都是線性的。”

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.

研究人員在背景資料中說，結腸癌是美國第三大最常見的癌癥，也是導致男性和女性癌癥相關死亡的第三大原因，預計2018年將有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.

他們說，大約每24個女性中就有1個，每22個男性中就有1個會在一生中患上結腸癌。

"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.

“長期以來，人們一直認為維生素D缺乏會導致骨質疏松癥和免疫系統(tǒng)功能紊亂之外的其他問題，”紐約Lenox Hill醫(yī)院的內科醫(yī)生倫霍洛維茨博士說，他沒有參與這項研究。

"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.

霍洛維茨說:“這項研究證實了維生素D缺乏可能導致癌癥的發(fā)生，維生素D缺乏與結直腸癌有關聯。”。

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

但是，也不要為了避免患結腸癌而去太陽下燒烤哦。

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.

麥卡洛說，只有大約7 %的美國人因為維生素D太少而增加了患結腸癌的風險。

"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."

麥卡洛說:“如果你一年四季都住在陽光明媚的地方，或者你住在春夏兩個月都比較溫暖的地方，你體內的維生素D水平自然就會更高。我們不建議人們尋求陽光照射來提高他們的維生素D水平，因為紫外線輻射是皮膚癌的一個很強的危險因素。”

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.

麥卡洛說，維生素D長期以來與骨骼健康相關，但由于研究一直不多，維生素D并未被推薦用于預防結腸癌或其他健康問題。

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.

她說，當美國國家醫(yī)學研究院在2011年發(fā)布維生素D指南時，它得出的結論是，維生素D對癌癥有益的醫(yī)學證據不足以提出建議。

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.

為了澄清這一點，麥卡洛和她的同事將來自17項不同研究的數據結合起來，這些研究涉及5，706名結腸癌患者和7，107名來自美國、歐洲和亞洲的健康參與者。

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.

研究人員甚至重新分析了大約三分之一的參與者的血樣，這樣他們就可以在所有17項研究中進行更直接的比較。

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

他們的結論是，維生素D確實能預防結腸癌，尤其是對女性。

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

麥卡洛說，大多數人在日常生活中就能獲得足夠的維生素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.

她說，你在街上隨意散步、跑腿，甚至從汽車里或者下火車后步行到辦公大樓時曬到的陽光足以刺激你體內適當的維生素D產生。

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.

麥卡洛說，人們還可以從牛奶、谷類食品和橙汁等強化食品中獲取維生素D，也可以從鮭魚、金槍魚、鱒魚和劍魚等肥胖的魚類中獲取維生素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.

正因為這些，人們不應該依靠補充劑來獲得維生素D，麥卡洛說。大劑量的維生素D可能有毒。

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

“不建議使用大劑量的個人補充劑，”她說。

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.

麥卡洛說，目前還不清楚為什么維生素D能預防癌癥，但研究人員懷疑維生素在控制細胞生長和促進程序性細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."

“當異常細胞不受控制地生長和擴散時，癌癥就會發(fā)生，”她說。實驗研究表明，維生素D有助于限制異常細胞的增殖。"

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

這項新研究于6月14日發(fā)表在國家癌癥研究所的期刊上。