A good night's sleep is often taken for granted until it is disrupted. There are many factors that can affect sleep. Often it's stress, anxiety and bedtime habits.
The last year has seen us endure drought, bushfires and COVID-19. The constant worry does not always switch off when our head hits the pillow.
To make it worse, our bedtime habits, alcohol, caffeine and screen time can affect our quality of sleep.
Stress and anxiety are associated with an increase in evening levels of the stress hormone cortisol, which has been shown to reduce the level of the neurotransmitter serotonin in the brain. Serotonin is important for sleep as it is a precursor to melatonin, a hormone involved in the sleep-wake cycle.
Increased serotonin has been shown to improve cognition and mood.
Elevated cortisol can cause fragmented sleep, insomnia and shortened overall sleep time.
The use of electronic devices, particularly at bedtime, can also reduce melatonin levels through exposure to bright light, particularly blue light, which can delay and disrupt our sleep cycle.
Drinking alcohol close to bedtime can affect sleep quality by causing frequent waking from an increased need to urinate, nightmares and/or night sweats. Alcohol is strongly associated with anxiety and depression, which may exacerbate existing conditions, further increasing the risk of disrupted sleep.
Caffeine is a well known stimulant, and consumption before bed can make it more difficult to get to sleep. Once asleep, its action as a diuretic can cause more frequent visits to the bathroom.
For many of us, a warm glass of milk, or herbal tea such as chamomile are part of our bedtime routines for their perceived sleep-inducing effects.
However, the question remains: is there a biological reason for why these aid sleep?
Milk (and other dairy products such as cheddar cheese) contains the amino acid tryptophan that is used for production of serotonin and melatonin. In chamomile tea, the flavonoid apigenin that binds to brain receptors is thought to produce sedative effects.
Nuts, seeds, salmon, poultry, leafy green vegetables, broccoli, bananas, kiwi fruit, tofu and eggs are also rich sources of tryptophan. These contain other essential vitamins, minerals and fatty acids that play a role in improving sleep directly or indirectly.
An amino acid found in green tea, L-Theanine, is an emerging candidate as a potential natural sleep aid. Several studies have shown that its consumption can lower stress and improve sleep. However, the evidence is preliminary and more research is warranted.
It should be noted that while these foods are rich sources of vitamins, minerals and other micro and macronutrients, the amounts of each of these compounds vary. Therefore, it is important to consume a healthy, varied diet to ensure we are getting ample amounts of these important biological compounds.
Response by: Amanda Bulman, Nathan D'Cunha, Associate Professor Andrew McKune, Associate Professor Nenad Naumovski, University of Canberra.
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