褪黑素安全吗？专家解释潜在风险和益处

Is Melatonin Safe? Experts Explain the Potential Risks - And the Benefits

文本难度：四级

刘立军供稿

As many as 70 million people in the U.S. have problems with sleep, and many are increasingly turning to melatonin supplements to help them fall asleep. People generally perceive these over-the-counter gummies, liquids and tablets as harmless. But recent research has raised new questions about whether the popular sleep aid is as benign as people assume, especially the longer it’s used.

美国有多达7000万人存在睡眠问题，其中越来越多人开始依赖褪黑素补充剂来助眠。人们普遍认为这类非处方的软糖、口服液和片剂无害，但近期研究却引发了新的担忧：这种广受欢迎的助眠产品是否真如人们所想的那样安全——尤其是在长期使用的情况下？

1. How does melatonin work in the body?

褪黑素在体内如何产生效果？

Melatonin is a hormone that humans naturally produce, as do all other mammals, including bears. It regulates the body’s circadian rhythm, the 24-hour biological “clock” that influences when we are sleepy or awake and alert. The body’s melatonin levels fluctuate in response to light – the brain’s control center for sleep suppresses levels during the day and boosts levels at night. As the hormone circulates in the bloodstream, it tones down the signals that keep us awake, but it doesn’t cause sleep, says Jennifer Martin, a psychologist at Florida International University. Instead of acting like a sedative, melatonin sends the body biological signals that it’s nighttime.

褪黑素是一种人体自然分泌的激素，其他哺乳动物（包括熊）也会产生。它负责调节人体的昼夜节律——即影响我们何时困倦、何时清醒或保持警觉的24小时生物“钟”。体内褪黑素水平会随光线变化而波动：大脑中控制睡眠的中枢在白天会抑制其分泌，夜间则提升其水平。佛罗里达国际大学的心理学家詹妮弗·马丁（Jennifer Martin）表示，当褪黑素在血液中循环时，它会减弱那些让我们保持清醒的信号，但并不会直接催人入睡。与安眠药不同，褪黑素向身体传递的是“天黑了”的生物信号。

2. What are melatonin’s short-term side effects?

褪黑素有哪些短期副作用？

Melatonin supplements are generally considered safe, but some people do report headaches, dizziness, or nausea after exposure. Taking too much at one time can disrupt sleep rather than improve it. Too much of the drug may also trigger something akin to a melatonin hangover the next day: lingering amounts in the blood can cause grogginess and tiredness.

褪黑素补充剂通常被认为是安全的，但有些人服用后会出现头痛、头晕或恶心等症状。一次性摄入过量不仅无助于改善睡眠，反而可能扰乱睡眠。剂量过高还可能引发次日类似“褪黑素宿醉”的反应：血液中残留的褪黑素会让人昏沉乏力、精神不振。

Supplements are sold with doses that are “much, much higher than anybody is naturally producing,” says Jamie Zeitzer, a sleep specialist at Stanford University. The hormone is commonly sold in five-milligram concentrations, though some “extra strength” products say they contain up to 40 milligrams.

斯坦福大学的睡眠专家杰米·蔡策（Jamie Zeitzer）表示，市面上销售的褪黑素补充剂剂量“远远高于人体自然产生的水平”。这类产品通常以5毫克的剂量销售，而某些“加强型”产品甚至标称含量高达40毫克。

“More isn’t better,” Martin says. “For a lot of people, a small dose is the most beneficial.”

“剂量并非越多越好，”马丁表示，“对很多人来说，小剂量反而效果最佳。”

Getting the right amount can be tricky. While the melatonin used in supplements is chemically identical to that produced in the body, the actual amount of the hormone in these products may not match what’s on their label. Some over-the-counter products contained anywhere from 80 percent less to about 470 percent more melatonin than advertised, a 2017 study found. Melatonin is sold as a supplement, which means such products reach the market without the Food and Drug Administration first evaluating their safety or production standards. Shalini Paruthi, a sleep medicine physician at John J. Cochran Veterans Hospital in St. Louis and spokesperson for the American Academy of Sleep Medicine, says to look for U.S. Pharmacopeia-certified products, which are tested for the quantity of their listed ingredients.

要摄入合适的剂量并不容易。尽管补充剂中的褪黑素在化学结构上与人体自身产生的完全相同，但产品中实际含有的激素量可能与标签所标注的不符。2017年的一项研究发现，某些非处方产品的褪黑素含量比标示值少80%或多出约470%。由于褪黑素是以膳食补充剂的形式销售，这类产品无需经过美国食品药品监督管理局（FDA）对其安全性或生产标准的预先审查即可上市。圣路易斯市约翰·J·科克伦退伍军人医院的睡眠医学医生、美国睡眠医学会发言人莎莉妮·帕鲁西（Shalini Paruthi）建议选择经美国药典（U.S. Pharmacopeia）认证的产品——这类产品会经过检测，确保其所含成分的计量与标签一致。

3. How does long-term melatonin use affect health?

长期使用褪黑素对健康有何影响？

At a conference in early November, researchers at SUNY Downstate Health Sciences University and their colleagues presented an analysis of U.K. medical records that raised concerns about long-term melatonin use. Almost 5 percent of 65,414 adults with insomnia who took melatonin for at least a year experienced heart failure (whereas almost 3 percent of those who did not take the sleep aid did so). People who took melatonin for at least a year were also more than three times as likely to be hospitalized for heart failure and nearly twice as likely to die from any cause compared with those who had no medical record of taking melatonin.

今年11月初的一场会议上，纽约州立大学下州健康科学大学（SUNY Downstate Health Sciences University）的研究人员及其同事公布了一项基于英国医疗记录的分析，引发了对长期使用褪黑素的担忧。在65414名患有失眠症的成年人中，约有5%服用褪黑素至少一年的人出现心力衰竭（而对于未服用褪黑素者，这一比例约为3%）。此外，与没有褪黑素用药记录的人群相比，服用褪黑素至少一年的人因心力衰竭住院的风险高出三倍以上，全因死亡风险也接近翻倍。

But some experts believe the findings, which have not yet been published or peer-reviewed, might say more about the consequences of poor sleep rather than melatonin use. “I don’t see a very good reason for melatonin to be directly involved in ,” Zeitzer says. Bad sleep is more likely to put extra pressure on the cardiovascular system, he says. Chronic insomnia is already known to be related to a higher risk of cardiovascular disease, metabolic dysfunction and issues with memory, learning and mental health. A more likely explanation for the new study’s trends is that people with poor sleep are relying on melatonin, which might not be helping them, Martin says.

但一些专家认为，这项尚未发表、也未经同行评审的研究结果，或许更多反映的是睡眠不足本身的危害，而非褪黑素直接所致。他指出，“我实在看不出褪黑素直接导致的合理机制，”蔡策表示。更可能的情况是，糟糕的睡眠给心血管系统带来了额外负担。事实上，慢性失眠已被证实与多种健康风险升高相关，包括心血管疾病、代谢紊乱，以及记忆力、学习能力和心理健康问题。马丁认为，新研究所观察到的趋势，更可能是由于睡眠不佳的人群在依赖褪黑素，而褪黑素可能并未真正改善他们的睡眠。

Other long-term studies haven’t found evidence that melatonin harms the heart. But there isn’t much substantial, long-term safety data for melatonin.

其他一些长期研究尚未发现褪黑素损害心脏的证据，但目前关于褪黑素长期使用的安全性，仍缺乏充分、可靠的数据。

4. How effective is melatonin as a sleep aid?

褪黑素作为助眠剂的效果如何？

The hype around melatonin is a bit misleading. In placebo-controlled trials, people who take melatonin fell asleep just seven minutes faster on average and slept about eight minutes longer than those who took a placebo. But improvements are larger when participants knew they were getting melatonin. The placebo effect might explain this finding, Martin says. “When you believe something will work, you tend to be a little more relaxed and fall asleep more quickly,” she adds.

围绕褪黑素的宣传具有一些误导性。在安慰剂对照试验中，服用褪黑素的人平均仅比服用安慰剂的人早7分钟入睡，总睡眠时间也只延长了约8分钟。然而，当受试者知道自己服用了褪黑素时，改善效果更为明显。马丁指出，这一现象可能源于安慰剂效应：“当你相信某种东西有效时，往往会更放松，从而更快入睡。”

Timing seems to matter, too. In one analysis, taking melatonin about three hours before bedtime and in four-milligram doses led to the greatest improvements. Clinicians typically recommend two-milligram supplements, however. The American Academy of Sleep Medicine recommends melatonin for some sleep issues related to time adjustments such as jet lag and shift work but not for insomnia.
服用时机似乎也很关键。一项分析显示，在睡前约三小时服用4毫克褪黑素，对睡眠的改善效果最佳。不过，临床医生通常推荐使用2毫克剂量的褪黑素。美国睡眠医学会推荐将褪黑素用于改善某些与时间调整相关的睡眠问题（如时差反应或轮班工作所引起的睡眠障碍），但不推荐将其用于治疗失眠症。

If melatonin works for you, keep using it, Zeitzer says. Evidence isn’t strong enough yet to show long-term use improves or worsens health, Martin says. She suggests people should work with a specialist if their sleep problems persist. “There are effective treatments for sleep disorders,” she says. “People don’t have to suffer.”

蔡策表示：“如果你觉得褪黑素对你有效，那就继续使用。”马丁则指出，目前尚无足够证据表明长期使用褪黑素会改善或损害健康。但她建议，如果睡眠问题持续存在，应寻求专科医生的帮助。“睡眠障碍是存在有效的治疗方法的，”她说，“人们不必默默忍受。”

【词汇】

1. melatonin n. 褪黑素（一种调节睡眠的激素）

2. benign adj. 良性的

3. hormone n. 激素

4. circadian adj. 昼夜节律的；生理节奏的

5. suppress v. 抑制

6. akin adj. 类似的；同类的

7. hangover n. 宿醉；（引申义）残留不适感

8. lingering adj. 拖延的，缓慢消失的

9. grogginess n. 昏沉；迷糊状态

10. milligram n. 毫克

11. over-the-counter product 非处方药

12. insomnia n. 失眠

13. cardiovascular adj. 心血管的

14. chronic adj. 慢性的

15. dysfunction n. 功能障碍

16. hype n. 大肆宣传；炒作

17. placebo n. 安慰剂

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