Diet and sleep go hand in hand. Sleeping poorly can influence our dietary habits, and poor diet and nutrition can negatively impact the quality and duration of our sleep. In this article, we break down how diet and sleep are linked and the impact this can have on health.
Usually, when we have a bad night's sleep, we tend to think about the activities we did the day before that could impact our restlessness, any emotional challenges we may be facing, such as increased stress or anxiety levels, or the role technology may have had on our sleeping pattern.
However, many seem to dismiss diet as a contributing factor when in fact, the two are linked. Research evidence is increasingly showing that diet can impact sleep, including duration and quality and that, in return, sleep can also influence food consumption and overall health.
How sleep duration affects food consumption
There's no doubt that sleep is an essential function of the human body.
The sleeping process allows both the body and mind to revitalise and reclaim a state of relaxation, enhance the body's ability to repair muscles and damaged cells, and carry out cognitive functions such as processing memories from short to long-term.
Without adequate sleep duration, the body cannot sufficiently repair itself, leading to emotional stress, impaired decision-making, and interest for this article, negatively impacting food consumption.
Sleep and hunger regulatory hormones
Food intake and appetite are regulated by the hormones leptin and ghrelin being released at different times in response to food – the release of ghrelin stimulates appetite and food intake, whereas leptin secretion promotes satiety, signalling to stop eating.
However, lack of sleep disrupts the balance of hormone secretion, which can lead to increased appetite and food consumption.
Leptin plays a role in food intake, energy expenditure, glucose, and fat metabolism and is produced by insulin-mediated glucose metabolism. During eating, the adipose tissue releases leptin to signal to the hypothalamus to stop eating. As energy requirements are low during sleep, leptin stays at a high level to signal that the body doesn't need food.
In contrast, ghrelin is a fast-acting hormone produced in the stomach and small intestine that stimulates the appetite by initiating gastric emptying and hunger to signal to the body to eat. During adequate sleep, as food intake isn’t required, ghrelin levels are low.
Impact of sleep deprivation on leptin and ghrelin
Image is taken from Spiegal et al. (2009) Effects of poor and short sleep on glucose metabolism and obesity risk. Nature Review Endocrinology. 5(5):235-61.
Studies have found that disturbed and/or reduced sleep duration reduces circulating leptin levels, increase ghrelin levels (as shown in figure 1), and increase self-reported hunger. This can lead to increased caloric consumption, poor dietary habits, snacking, and increased meals per day.
Spending more time awake also increases the opportunity to eat, but it may lead to increased food consumption and potential weight gain when coupled with an increase in hunger and appetite.
The result when it comes to food consumption
Reduced sleep can lead to an increased reward sensitivity to calorie-dense foods, likely to try and compensate for the disruption in energy levels by promoting the consumption of energy-rich foods.
Evidence shows that short sleepers tend to choose foods that are weight-gain promoting, either higher in fats or refined carbs, caffeine, and sugar, and they typically consume less fruit and vegetables than those who sleep between 7-9 hours a night.
Short sleepers are also more likely to have impaired glucose metabolism, thyroid function, and higher inflammation as a result.
Food choices and their effect on sleep quality
Though the recommendation to sleep 8 hours is heavily advised, that falls under the assumption that we’d be getting good quality sleep every time.
However, it's hard to tell whether sleep quality is adequate or not in comparison to literal measures such as sleep deprivation.
Poor quality sleep can negatively impact glucose metabolism, the ability to convert memories from short to long-term, and it can disturb the production of sleep regulatory hormones - endogenous melatonin, and serotonin which the body uses to synthesise melatonin during sleep. This, in turn, affects appetite, reduces productivity and concentration levels, and increases body weight.
Diet research is increasingly building to show that eating certain foods and nutrients can either worsen or improve sleep quality.
Beneficial food and nutrients for sleep quality
Various nutritional intervention studies have shown that sleep could be improved when certain foods and nutrients are incorporated into the diet, including:
- Melatonin-rich foods (banana, coconut, oats)
- Tryptophan-rich protein
- Tart cherry juice
A study found that foods high in melatonin, tryptophan, and phytonutrients - phenolic acids and flavonoids – in particular, seem to improve sleep quality. It's hypothesized that consuming melatonin and tryptophan can help regulate the sleeping cycle, whilst phytonutrients can enhance intercellular communication and reduce inflammation.
Foods that negatively impact sleep quality
In contrast, there are many other food and nutrients that are associated with lower sleep quality, mostly:
- Sweetened beverages
- Energy drinks
- High levels of protein
- And deficiencies in vitamin B1, folate, phosphorus, magnesium, iron, zinc, and selenium with shorter sleep duration.
It's thought that the high levels of glucose in the bloodstream resulting from sugar-rich foods impacts insulin production, which can affect sleep quality. However, many researchers suggest that more studies and interventions should be conducted to determine diet’s impact on lower sleep quality.
How sleep and diet can impact our health
The length of sleep and quality can sometimes be an unclear factor in developing certain health conditions and should not be overlooked.
Regular, disturbed sleep encourages shorter sleep duration overall and lower-quality sleep, increasing the risk of inflammation and associated diseases.
Frequent epidemiological studies have gathered evidence to link regular poor sleep with increased weight, appetite stimulation, and a higher risk of serious chronic diseases, including obesity, heart disease, and diabetes.
According to the NHS, those who sleep less than 7 hours a night gain more weight and are at a higher risk of obesity than those who sleep for 7 hours.
As obesity is a leading factor in developing many chronic diseases, not identifying poor sleeping patterns as a contributing factor could potentially offer worse health outcomes.
Obesity has been associated with short sleep duration. Our founder, Professor Janet Cade, links high BMI and waist circumference to short sleepers compared to those who sleep the recommended time, who tend to have lower BMI and more favourable metabolic profiles.
In addition to the development of disease, it can also shorten life expectancy.
The balancing act of diet and sleep
Both sleeping and dietary habits need to be considered to improve the other.
Though more research needs to be conducted into the preliminary findings of connecting diet and sleep, the building evidence has shown how much we sleep, sleep quality, and what we eat can affect the body's restorative abilities and health outcomes.
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