Sleep: How does your diet affect sleep?

A substantial amount of evidence supports the fact that a lack of sleep or poor-quality sleep affects our diet choices the next day. But what about if we reverse that? Do the foods we eat affect our sleep?

The evolution of sleep

The sleep habits of humans have evolved significantly over the centuries. Sleep has always been vital for human functioning and overall health, even hundreds of years ago. In fact, we spend over 30% of our lives sleeping (Golem et al., 2014).

Sleep patterns in humans were drastically different around the 16th and 17th centuries. There are reports that humans practised polyphasic sleep, which means they used to sleep for multiple periods each night (Samson & Nunn, 2015). This would typically involve sleeping in two, four-hour periods, with a two-hour break between. Nowadays, humans have a monophasic sleep pattern. This means we sleep for one long period each night.

Circadian rhythms are a 24-hour cycle in which our body undergoes physical, mental, and behavioural changes (Suni, 2022). These processes respond to light and darkness. During the day, our body responds to light and sends signals through our system to keep us awake and alert. Our body responds to darkness at night and produces melatonin, a hormone that promotes sleep. Centuries ago, before electricity, humans followed this day-night schedule meticulously. As there was little for humans to do without light, the night was reserved primarily for sleep.

Technology has evolved and advanced over the centuries, which means humans can do more with their nights. With the natural light and dark cycle no longer restricting what we can do, we have been working later into the night. Distractions such as mobile phones, television programmes, and travelling also affect our circadian rhythms and have taken a toll on the quality and quantity of our sleep (Shochat, 2012). Over the last decade, researchers have been looking into other factors that affect our sleep, including diet.

What is good quality sleep?

Good quality sleep is how well you sleep, usually involving falling asleep quickly, not awakening during the night, and having a long sleep duration (Binks et al., 2020). What you eat is believed to play a significant role in sleeping well (Zhu et al., 2019).

How does your diet affect how you sleep?

It is well known that sleep quality influences a person’s diet choices and overall health. However, researchers have recently established links between how your food/kai choices can affect how well you sleep.

As a general rule, a balanced, healthy diet high in plant foods and low in processed sugar and foods is associated with good quality sleep (Godos et al., 2021). A balanced, healthy diet for adults is outlined in the Ministry of Health’s (2020) Eating and Activity Guidelines

Further information on these guidelines and material to support implementing them in your life can be found on the NZNF website.

The relationship between diet and sleep is complicated as nutritional factors vary dramatically with diet patterns and depend significantly on every individual’s complex, interconnected body systems (Zhu et al., 2019). However, promising findings suggest an association between specific foods/kai and sleep quality (Godos et al., 2021).

What foods/kai are good for promoting sleep?


You’ve probably heard of a grandparent, parent, or friend who enjoys a glass of milk before bed to make them more relaxed and drowsier. The age-old tale of milk promoting sleep does show some encouraging evidence. Recent data has found foods containing tryptophan, an amino acid found in milk, may be linked with improved sleep outcomes (Binks et al., 2020; Komada et al., 2020). Tryptophan assists in producing serotonin and melatonin. Serotonin is a neurotransmitter known for inducing feelings of calmness and drowsiness. Melatonin is a hormone that helps you feel like sleeping at night (Pacheco, 2022; Peuhkuri et al., 2012). Consumption of milk, even warm milk (if you prefer), may increase sleep duration and reduce the time it takes to fall asleep (Binks et al., 2020; Pacheco, 2022).

So, will a glass of milk before bed help me get to sleep?

It is still difficult to confirm a definite correlation between milk consumption and improved sleep quality due to individual differences, consumption times and consumption volumes. Overall, if you enjoy milk, this could be a great option to explore to help you feel sleepy and relaxed before bed.


Emerging evidence suggests a relationship between carbohydrate consumption and improved sleep. Some carbohydrates could significantly affect sleep structure, sleep onset, and continuation (Vlahoyiannis et al., 2021). However, there is a lot of conflicting evidence available on this topic. The type and quality of the carbohydrate must be considered rather than assuming that all carbohydrates affect sleep. This is a food group whose impact on sleep is developing interest, and we will continue to update this article as evidence grows.

Tart cherries and kiwifruit:

Tart cherries and tart cherry juice have been investigated to understand their effect on sleep. Tart cherry consumption has shown promising evidence that they can improve sleep quality (Howatson et al., 2012; St-Onge et al., 2016). Tart cherries have a high melatonin concentration, a hormone that regulates circadian rhythms and promotes a healthy, long sleep (Howatson et al., 2012; Suni, 2022).

Fun fact:

Tart cherries (formally: Montmorency cherries) are different to the sweet cherries you often buy fresh at the supermarket in summer. While tart cherries are common in the USA, they are hard to find in NZ. You may, however, be able to buy tart cherry juice- ideally it should be low in added sugars.

Kiwifruit, a New Zealand classic, is another fruit that may improve the quality of your sleep (Lin et al., 2011). One study found eating two kiwifruits one hour before bed improved the onset, duration, and efficiency of sleep (St-Onge et al., 2016). A property of kiwifruit that is thought to enhance sleep is its high concentration of serotonin, another hormone that aids in promoting sleep (St-Onge et al., 2016). Kiwifruit is grown in abundance throughout New Zealand, so it is likely to be a more accessible and cost-effective sleep aid than tart cherries. Overall, both tart cherries and kiwifruit have been associated with improving sleep. However, further study is needed to draw firm conclusions.


Increasing evidence suggests adequate vitamin intake is essential to achieving quality sleep. Inadequate intake of several micronutrients, including calcium, magnesium, and vitamin A, C, D, and K, have been associated with poorer sleep (Ikonte et al., 2019; St-Onge et al., 2016). Nuts, including almonds, walnuts, pistachios, and cashews, are high in minerals such as magnesium and zinc. The consumption of these foods could increase your micronutrient intake (Suni, 2022). The extent to which micronutrients affect sleep remains unclear, but an association has been established (Frank et al., 2017).

Intermittent fasting:

Intermittent fasting has become a popular diet for people who want to lose weight. The relationship between intermittent fasting and sleep has been reviewed. The majority of studies found both time-restricted fasting (eating all food within a 4-10h window in 24 hours) and alternative day fasting (reduced calories on alternative days) did not affect sleep quality and quantity, however, authors note that more research is required in this area(McStay et al., 2021). However, if it helps you to sustainably reduce excess weight it may benefit your health and sleep quality (McStay et al., 2021). If you want to know more about intermittent fasting, please explore the NZNF article.

It is possible that different fasting schedules impact your sleep differently. Ideally, you want to avoid going to bed feeling hungry or too full. A grumbly tummy can make it harder to fall asleep peacefully. On the other hand, being too full close to bedtime (from, for example, heavy dinners and late-night snacking) gives your digestive system less time to rest, may disrupt your body’s natural circadian rhythm (Asher et Sassone-Corsi, 2015) and can trigger reflux (as food doesn’t digest as well if you are lying down). For these reasons, it’s recommended to keep at least a 2-hour gap between eating and going to bed.

What foods/kai are disrupting our sleep?

Added sugar:

A diet high in added sugar can negatively affect sleep (Alahmary et al., 2022). The majority of evidence suggests high consumption of foods and drinks with added sugar, including sugar sweetened beverages, energy drinks and confectionary, is associated with shorter sleep duration and poorer quality of sleep (Alahmary et al., 2022; Godos et al., 2021; Zhu et al., 2019). As well as poorly affecting sleep, added sugar increases the risk of heart disease, diabetes, and obesity (Alahmary et al., 2022).

How much sugar should I be consuming?

The World Health Organisation recommends that an adult diet should be made up of less than 10% sugars and added sugar (Alahmary et al., 2022). This is equivalent to 50g of sugar or 12 teaspoons per day (WHO, 2020). Ideally, sugar should be less than 5% of total energy intake for additional health benefits.


Researchers gathered evidence and found that not having caffeine for an entire day effectively improves sleep quality (Sin et al., 2009). However, if you cannot go the day without a much-loved caffeinated beverage, it is recommended you do not consume a drink high in caffeine later than six hours before you sleep (Pacheco, 2022). This is because caffeine has a six-hour half-life. For example, if you go to bed at 10pm, your last caffeinated beverage should not be consumed later than 4pm. Consumption of caffeine impacts sleep quality by delaying sleep onset, decreasing total sleep time, and increasing sleep disturbances (O’Callaghan et al.,  2018).

Can a cup of tea improve your sleep?

Some research indicates teas, especially herbal teas such as chamomile and green, can promote relaxation and sleep (Baek et al., 2018). However, evidence is still limited. If you enjoy a cup of tea before bed, it is an excellent alternative if you are trying to kick a caffeine habit.


Excessive consumption of alcohol can contribute to poor quality sleep (Park et al., 2015). While alcohol has a sedative effect, studies have found alcohol consumption was not related to improved overall sleep (Park et al., 2015; Thakkar et al., 2015). In fact, research has indicated that alcohol consumption is correlated with difficulty maintaining sleep and shorter sleep duration (Park et al., 2015). Even a low consumption of alcohol can negatively affect your sleep. Less than two drinks for men and less than one for women reduces sleep quality by 9.3% (Pacheco, 2022). More than two drinks for men and one drink for women decreases sleep quality by 39.2% (Pacheco, 2022). Alcohol is found to disturb sleeping patterns and is strongly suggested to not be used as a sleep aid (Irish et al., 2015).

Does alcohol help you sleep?

Alcohol will not help or improve your seep. While alcohol has sedative effects, it will cause disruptions later in your sleep cycle (Irish et al., 2015; Pacheco, 2022). This can result in you becoming more tired the next day.

Other factors that influence sleep:

Body weight:

Poor quality sleep is associated with a higher risk of obesity or high body fat (Barnes & Spreitzer, 2015; Rahe et al., 2015). Obesity is also a risk factor for obstructive sleep apnoea (Bove et al., 2018). This is a condition where individuals may periodically stop breathing throughout their sleep (Barnes & Spreitzer, 2015). This prevents individuals from getting a night of good quality sleep. However, losing weight can improve sleep. Adopting healthy behaviours, such as eating healthy foods and exercising (review the Eating and Activity Guidelines by the Ministry of Health) can help you lose weight, improve the quality and quantity of your sleep and relieve the symptoms of sleep apnoea (Brown, 2013).


The environment that you sleep in has a massive effect on your sleep. Excessive light can disrupt circadian rhythms (Aulsebrook et al., 2018; Blume et al., 2019). Artificial lights can prevent you from falling asleep and should be switched off or reduced as much as possible (Aulsebrook et al., 2018).

Environmental noise can also delay sleep onset and lead to sleep structure changes, therefore reducing sleep quality (Muzet, 2007). However, some people enjoy ambient sounds and soft music that may mask other noises to promote sleep (Trahan et al., 2018).

Your mattress and bedding can also impact your sleep. However, this is likely down to personal preference, body weight, and sleeping position (Pacheco, 2022). It is recommended you choose bedding, a pillow, and a mattress that you find most comfortable to enhance your sleep.

It would be best if you designed a sleep environment to suit your needs. So, make an environment that feels safe and appropriate for you!


Excessive stress can impact a person’s ability to fall asleep and stay asleep (Han et al., 2012). However, the relationship between stress and sleep is complex (Sanford et al., 2014). The Sleep Foundation recommends some tips to manage stress and improve sleep. These include staying away from electronic devices before bed, ensuring you are not consuming any caffeinated beverages before bed, and optimising your bedroom environment by dimming lights and reducing noise (Fry, 2022).

Summary of recommendations to improve sleep:

Evidence is still developing as to what specific foods directly impact sleep. However, some relationships have been established.

Overall, to improve your sleep:

  • Try to eat at least two hours before bed to ensure you have digested your food before bedtime – this reduces your risk of acid reflux (Suni, 2022).
  • Limit caffeine intake, particularly in the afternoon or at least six hours before sleep.
  • Avoid alcohol consumption as even one drink can disrupt your sleep cycle.
  • Milk, tea, kiwifruit, and tart cherries are a few foods you could explore that may help you sleep.
  • Ensure you create a suitable sleep environment that is tailored to your needs.
  • Most importantly, maintain a healthy lifestyle and eat healthy kai! This will positively impact your sleep and overall health.

More info

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Last modified: July 4, 2022