“睡前喝牛奶有助睡眠”的说法由来已久。为了改善睡眠状况，不少人都有睡前喝热牛奶的习惯。但喝牛奶真的能让我们睡得更好吗？牛奶助眠是一种心理安慰，还是有科学依据？我们来一起探究牛奶与睡眠的关系吧。
May help some people fall asleep faster
喝牛奶可能让一部分人更快入睡
A handful of small animal and human studies demonstrate that consuming dairy products like milk and cheese before bed may help some people have a more restful night’s sleep, though the reason why remains unclear.
一些对小动物和人类的研究表明，睡前饮用牛奶和食用奶酪等乳制品可以帮助一些人睡得更安稳，但原因尚不清楚。
Most experts agree that milk’s sleep-promoting potential is likely related to specific chemical compounds or the psychological effects of having a soothing bedtime routine — or perhaps a combination of the two.
大多数专家认为，牛奶促进睡眠可能与某些化学物质有关，也可能与这一放松的睡前习惯所产生的的心理效应有关，或者两者兼而有之。
May promote healthy sleep cycles
促进健康的睡眠周期
Certain compounds in milk — specifically tryptophan and melatonin — may help you fall asleep.
牛奶中的某些化合物，特别是色氨酸和褪黑素可以帮助你入睡。
Tryptophan is an amino acid found in a variety of protein-containing foods. It plays an important role in the production of the neurotransmitter known as serotonin .
色氨酸是一种氨基酸，存在于多种含蛋白质的食物中。它对合成神经递质5-羟色胺起着重要作用。
Serotonin boosts mood, promotes relaxation, and functions as a precursor in the production of the hormone melatonin.
5-羟色胺能改善情绪，有助于放松，是褪黑素产生的前体。
Note:
melatonin n. 褪黑素
Melatonin, also known as the sleep hormone, is released by your brain. It helps regulate your circadian rhythm and prepare your body for entering a sleep cycle.
褪黑素，也称为睡眠激素，由大脑释放。它有助于调节昼夜节律，让你的身体为进入睡眠周期做好准备。
Note:
circadian adj. 昼夜节律的，生理节奏的
The role of tryptophan and melatonin in sleep disorders is well established, and studies have found that taking supplements of these compounds may improve sleep and reduce symptoms of anxiety and depression that can crop up at bedtime.
色氨酸和褪黑素在治疗睡眠障碍中的作用已得到证实，研究发现，补充这些化合物可以改善睡眠，减少睡前可能出现的焦虑和抑郁症状。
Note:
crop up（尤指意外地）出现，发生
However, there’s currently no evidence to suggest that a single glass of milk contains enough tryptophan or melatonin to significantly influence your body’s natural production of melatonin or to independently treat a disordered sleeping pattern.
然而，目前没有证据表明一杯牛奶中含有足够的色氨酸或褪黑素，可以显著影响身体褪黑素的自然生成，或者独立治疗睡眠紊乱。
Psychological effects
心理效应
Some experts suspect that milk’s potential role as a sleep aid has little to do with its nutritional profile and that it’s instead more closely related to the psychological effect of having a calming bedtime ritual.
一些专家怀疑，牛奶作为助眠剂的潜在作用与其营养成分无关，相反，它与平静的睡前习惯所产生的心理效应关系更为密切。
Another theory is that drinking warm milk could subconsciously remind you of having milk at bedtime during your early childhood years. These soothing feelings may signal to your brain that it’s time to sleep, making it easier to drift off peacefully.
另一种理论认为，喝温牛奶能让你下意识地想起自己在幼年时期睡前喝牛奶的记忆。这些舒缓的感觉可能会向你的大脑发出信号，告诉你该睡觉了，让你更容易平静地入睡。
Still, there’s not enough evidence to guarantee any particular result from adding milk to your bedtime routine.
尽管如此，没有足够的证据来证明在睡前养成喝牛奶习惯会有什么特别的效果。
SUMMARY
总结
Milk contains several compounds known to support healthy sleep cycles. Plus, the psychological effects of a bedtime routine that includes milk may improve your ability to fall asleep, but more research is needed.
牛奶中含有几种已知的有助健康睡眠周期的化合物。此外，睡前喝牛奶这个习惯的心理效应可能会帮你更快入睡，但还需要更多的研究。
