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【注意】熬夜与癌症间的关系首次被确立
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【注意】熬夜与癌症间的关系首次被确立 美国科学家最新研究显示，晚上开灯睡觉或熬夜是导致女性患乳腺癌的主要因素之一。此报道也是基于先前数年的研究结果。由美国国家癌症研究所和美国国家环境卫生科学研究所共同进行的研究，为非自然光与癌症之间的关系提供了“首份证据”。 报道说，大量研究表明那些需要值夜班的职业妇女，如护士、空中乘务员，她们患乳腺癌的风险最高可达60％。此外还有研究表明，每周熬夜2到3天的女性也同样易患乳腺癌。 研究人员认为，夜间的灯光妨碍了褪黑素（Melatonin）的生成，而褪黑激素在抑制癌细胞生长的同时也会增强免疫系统。当前研究表明，Melatonin与多种癌症的形成均有关系，如乳腺癌，皮肤癌等。 在最近的研究中，研究人员将乳腺癌的肿块移植到老鼠身上，并给这些老鼠分别注入取自清晨或夜间经电灯照射之后的老鼠血液。研究发现清晨（也就是睡眠之后）的血液使癌细胞的生长速度减缓了80％，而电灯照过的血液加速了癌细胞的生长。 专家建议，睡觉时关闭所有电灯，因为睡在全黑的房间中有利于制造神经传递物质血清素，这对制造褪黑激素至关重要；尽量保持9小时睡眠；早上起床后到户外走走。 The nighttime hormone melatonin puts breast cancer cells to sleep. It also slows breast cancer growth by 70% David E. Blask, MD, PhD, of Bassett Research Institute in Cooperstown, N.Y., reported the findings at this week's annual meeting of the American Association for Cancer Research. Breast cancers get revved up by a kind of dietary fat called linoleic acid. Melatonin interacts with linoleic acid, so he gave melatonin to mice implanted with human breast cancers. "This breast cancer rev-up mechanism gets revved down by melatonin," Blask said at a news conference. "Nighttime melatonin is a relevant anticancer signal to human breast cancers. Ninety percent of human breast cancers have specific receptors for this signal." The hormone seeps from a pea-sized gland in the brain when the lights go out at night. It's the reason you get sleepy when it's dark. Blask and colleagues found that melatonin puts cancer cells to sleep, too. Blask's team exposed lab mice with human breast cancers to constant light. Tumor growth skyrocketed. "With constant light, tumors grow seven times faster and soak up incredible amounts of linoleic acid," he says. "During the day, the cancer cells are awake and linoleic acid stimulates their growth. But at night cancer cells go to sleep. When we turn on lights at night for a long time, we suppress melatonin and revert back to the daytime condition." The finding may explain why nurses who often work the night shift have high rates of breast and colon cancer. Blask says clinical trials are under way to see whether melatonin supplements can help treat cancer. It may also help in other ways. "When you take melatonin prior to normal onset of sleep, it will [jump-start the sleep cycle]," he notes. "Many cancer patients suffer from sleep problems. Melatonin may also improve the quality of life in cancer patients by helping them sleep." Arizona Cancer Center researcher David Alberts, MD, notes that there is a lot of interest in melatonin as a sleep inducer. However, he worries about the safety of over-the-counter melatonin supplements. "The issue is safe dosing of melatonin," he said at the AACR news conference. Provided that melatonin supplements actually contain the hormone, Blask isn't worried about overdose. "In human studies, melatonin has basically no toxicity," he tells WebMD. "Now it takes very little melatonin to stimulate nighttime sleepiness -- on the order of three-tenths of a milligram. But you can't overdose with melatonin. People have taken gram quantities. Its nastiest side effect is sleepiness." |
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2楼2006-08-22 05:33:51
