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.”


参考译文：
据一份新研究报道，那些有着较高α-胡萝卜素含量水平的人们比低含量水平的人寿命更长，而且死于心血管疾病及心脏病的几率也更小。α-胡萝卜素，是一种橙色果蔬含有的抗氧化剂，像胡萝卜、冬瓜、橙子和柑橘等。

这项研究未证实两者之间的因果关系，只是说明两者有联系。以前曾有研究人员做过数次严密的临床试验来证明两者内在联系，但结果往往不如人意。

不过，这项研究发现还是令人振奋的。研究中，疾病预防控制中心的研究人员分析了一万五千多名参与第三次全国健康与营养调查(1988-1994)跟踪调查的成年人的血样中α-胡萝卜素含量。

至2006年，研究人员确定有3810名调查参与者已死亡。那些血液中α-胡萝卜素水平最高者，即便年龄、体质指数(body mass index)、是否吸烟等参数改变后，他们活得更久的可能性依旧很大。

与那些体内含α-胡萝卜素这种抗氧化剂水平最低者相比，高浓度与中等浓度含量者长寿的可能性分别提高40%和27%。

疾病预防控制中心的流行病学家李朝阳博士(Chaoyang Li)—11月22号《内科学文献》刊出了其为第一作者的一份研究，表示：“这个发现非常值得注意，”并补充道，“虽然α-胡萝卜素水平或许只是健康生活方式的一个方面，但试验发现它能抑制癌细胞的生长，我们还需要更深入的研究。”