People with high blood levels of alpha-carotene — an antioxidant found in orange fruits and vegetables like carrots, winter squash, oranges and tangerines — live longer and are less likely to die of heart disease and cancer than people who have little or none of it in their bloodstream, a new study reports.

The study does not prove a cause-and-effect relationship, only an association; in the past, rigorous clinical trials of such correlations have often had disappointing results.

Still, the study’s results are intriguing. Researchers from the Centers for Disease Control and Prevention analyzed alpha-carotene levels in blood samples from more than 15,000 adults who participated in a follow-up study of the third National Health and Nutrition Examination Survey, known as Nhanes, from 1988 to 1994.

By 2006, researchers determined, 3,810 of the participants had died. But those with the highest levels of alpha-carotene were more likely to have survived, even after the scientists controlled for variables like age, body mass index and smoking.

Those with the highest concentrations of the antioxidant were almost 40 percent less likely to have died than those with the lowest; those with midrange levels were 27 percent less likely to die than those with the lowest levels.

“It’s pretty dramatic,” said the lead author, Dr. Chaoyang Li, a C.D.C. epidemiologist, whose study was published online on Nov. 22 in the Archives of Internal Medicine. While alpha-carotene may be no more than an indicator of other aspects of a healthy lifestyle, studies have found that it inhibits the growth of cancer cells in the laboratory, he said, adding, “We need more research.”


參考譯文：
據一份新研究報道，那些有著較高α-胡蘿卜素含量水平的人們比低含量水平的人壽命更長，而且死于心血管疾病及心臟病的幾率也更小。α-胡蘿卜素，是一種橙色果蔬含有的抗氧化劑，像胡蘿卜、冬瓜、橙子和柑橘等。

這項研究未證實兩者之間的因果關系，只是說明兩者有聯系。以前曾有研究人員做過數次嚴密的臨床試驗來證明兩者內在聯系，但結果往往不如人意。

不過，這項研究發現還是令人振奮的。研究中，疾病預防控制中心的研究人員分析了一萬五千多名參與第三次全國健康與營養調查(1988-1994)跟蹤調查的成年人的血樣中α-胡蘿卜素含量。

至2006年，研究人員確定有3810名調查參與者已死亡。那些血液中α-胡蘿卜素水平最高者，即便年齡、體質指數(body mass index)、是否吸煙等參數改變后，他們活得更久的可能性依舊很大。

與那些體內含α-胡蘿卜素這種抗氧化劑水平最低者相比，高濃度與中等濃度含量者長壽的可能性分別提高40%和27%。

疾病預防控制中心的流行病學家李朝陽博士(Chaoyang Li)—11月22號《內科學文獻》刊出了其為第一作者的一份研究，表示：“這個發現非常值得注意，”并補充道，“雖然α-胡蘿卜素水平或許只是健康生活方式的一個方面，但試驗發現它能抑制癌細胞的生長，我們還需要更深入的研究。”