It's 2 a.m. and you're in bed. Still awake. You fidget, you're unsettled and your mind is racing. You look at the clock, get anxious at how long it's taking you to fall asleep, wait, look at the clock again and feel even more anxious. It's an irritating cycle.
We all have our own remedies to help us fall asleep. Meditation, mindfulness, physical activity, a glass of wine, a few games of solitaire on your phone...
One of the most common go-to sleep remedies is drinking a cup of warm milk -- but is this just an old wives' tale or is warm milk really the answer to those sleepless nights?
According to Drew Dawson, a sleep and fatigue expert and director at Appleton Institute at Central Queensland University, drinking milk may help, but not for the reason you think.
"It can help some people fall asleep, but it's a bit of an old wives' tale," Dawson told The Huffington Post Australia. "It hasn't really been put to the test experimentally."
The common thought is that milk can help people fall asleep because it contains two substances which are known to be related to sleep and relaxation: the hormone melatonin and the amino acid tryptophan.
"Tryptophan is an essential amino acid that is not produced by humans but needs to be ingested in foods," Naomi Rogers, sleep expert and professor at the University of Sydney, told HuffPost Australia.
Foods that contain tryptophan include milk, turkey, pork, chicken, beef, some cheeses, eggs and bananas -- however, usually in very small amounts.
"Tryptophan is a precursor for the neurotransmitter serotonin (often called the 'feel good hormone'), which in turn can be converted into the hormone melatonin, which is secreted at night and is often called the 'hormone of darkness'," Rogers explained.
Though milk and serving temperature are not likely to influence sleep onset, warm milk may have psychological significance.
"Melatonin levels are low or non-existent during the day, and secretion starts about two hours prior to habitual bedtime. Melatonin is important for telling the body what time of day it is and is an important part of the circadian system.
"Melatonin is also thought of by many as a sleep hormone, either directly having a sleep inducing effect or as a time cue marker, starting off the normal physiological processes that lead to sleep."
Despite milk's tryptophan content, Dawson says the amount present in a glass of milk is lower than what would be contained in a melatonin supplement and that, for the average person, the dose is probably too low to feel the effects.
"There is some evidence that drinking milk can increase the levels of tryptophan, so in people whose sleep onset was due to tryptophan deficiency (which is very few) it may help," Dawson said.
"There is no really good research of milk working. What it does say which is interesting, for people with lactose intolerance it's not a good idea."
If only it were this easy.
While it's unlikely a glass of warm directly helps induce sleep, both Dawson and Rogers admit that warm milk can help for an entirely different reason.
"Though milk and serving temperature are not likely to influence sleep onset, warm milk may have psychological significance," Dawson told HuffPost Australia. "The routine of drinking a glass of warm milk may elicit memories of mum, home and childhood which may help us to relax."
Rogers adds that, if drinking milk before bedtime is part of your nightly routine, it may be the familiar action of having a warm glass of milk which is key.
"Our brains and physiology like routine and predictability, so if someone has a routine each night of, say, watching the late news, having a warm glass of milk, brushing their teeth and getting in to bed for sleep, then the brain and our physiology recognise this behaviour as part of the preparatory process for sleep and respond accordingly, making it easier to fall asleep once we are in bed," Rogers told HuffPost Australia.
Dawson also explains that it may be the distraction of getting up and thinking about something other than falling asleep which does the trick.
"It could be that it just takes you 10 minutes to make a cup of milk and by that time you're relaxed enough to fall asleep," Dawson said.
Well, are there any other foods or drinks that can help us fall asleep?
"Yeah, benzodiazepine food, maybe," Dawson said. "There is some vague literature about certain foods that are meant to promote sleep, but they're usually for people deficient in that particular vitamin or mineral.
"There are some studies around food supplements that improve sleep onset and they are related to low GI meals and also foods that are rich in magnesium and potassium. There is also some research on kiwifruit but I wouldn't be buying shares in it."
Practising meditation and drinking 'sleepy time' tea may help, too.
Roger, on the other hand, says that one macronutrient in particular can help people fall asleep more easily.
"Often meals rich in carbohydrates seem to make people feel sleepy, rather than meals higher in proteins," Roger explained.
"More likely are foods which make you not sleep," Dawson said. "So, a lot of people have indigestion related to chilli and alcohol which wakes you up or keeps you awake."
The other more commonly known factor which can prevent sleep is caffeine intake.
"The main 'food' that keeps people awake would be caffeine, although this does not occur in everyone as there is usually someone who boasts being able to drink an espresso at 10 p.m. and still fall asleep," Rogers said.
"The effects of caffeine on wakefulness depend on a person's age, their usual caffeine intake and their metabolism. For some people a coffee at lunch time may result in caffeine levels at bedtime that are high enough to make it hard to fall asleep."
Basically, don't put all your eggs in one basket. While, scientifically, these sleep remedies aren't 100 percent proven, sleep is such a personal -- and often sensitive -- experience, so what might help one person might do nothing for the next.
If you are experiencing persistent sleeping problems and it's affecting your day-to-day life, see your GP or health professional.