Updated: Dec 10, 2019
Did you know that we will spend on average 30% of our lives sleeping? (1) I remember my younger self saying things like : “I will sleep when I am dead”, “Sleep is for the weak” or '' I don't have time to sleep, I will just have more coffee'' … Well, needless to say I was completely wrong. Sleep is a major lifestyle factor, not only for survival, but also for overall health. Sleep has an impact on cognitive function, physical health and emotional well-being (1). We all experience a bad night of sleep and felt grumpier for no particular reason the next day? #grumpypants
Why is sleep important?
Even though we may feel that nothing is happening when we sleep, there are many physiological processes occurring, such as physiological and neurological processing and restoration. During sleep, we experience numerous changes, for instance, alterations in brainwave activity, reduction of the heart rate, slow down of respiration, blood oxygen saturation and reduce blood pressure (1). These changes reduce energy expenditure and help to initiate/sustain sleep. There are 2 main types of sleep phases: non-rapid eye movement (NREM) and rapid eye movement (REM). NREM is also known as “deep sleep” or “recovery sleep”. REM is the period when we dream and where memory is consolidated. They both occur for a few minutes in succession in a sleep cycle repeated 5-7 times per night (1).
What happens to our body when we don't sleep enough?
Sleep loss impairs several aspects of our health. Inadequate sleep has been associated to decrease performance and post-physical activity recovery, decrease cognitive performance, attention, memory, mood, poor speed and accuracy of tasks and heightened emotional reactivity (1,7) #notagoodtime. It is also linked with increased inflammation in the body, alteration of sympathetic nervous system activity and hormonal levels (1). Regarding chronic diseases, sleep restriction (<7 h/night) is associated with higher risk and incidence of cardiovascular disease, hypertension, hypercholesterolemia and alteration in glucose tolerance (associated with type 2 diabetes) (1). Compared to average duration sleepers (7-8h/night), epidemiological studies observed that short sleepers are more likely to have a higher body mass index, fat percentage and abdominal circumference (2). What are the mechanisms and reasons behind this? Continue reading!
How does sleep impact our nutrition?
Many meta-analyses and reviews report an inverse correlation between sleep and weight. Two main aspects can explain why poor sleep can be a factor leading to a higher fat percentage and even some chronic diseases: it has an influence our food choices and can impact metabolism.
1. Food Choices
To start, studies have reported that short sleepers (<6 hours of sleep/night) tend to have irregular eating habits, to consume fewer vegetables and to eat more snacks between meals (5). Logically, less time asleep equals more time awake, which means more opportunities to eat... Therefore, this can lead to a food intake higher than energy needs which leads weight gain (5). Also, many studies in a review from 2015 noticed that short sleepers are more likely to have diets high in fat and carbohydrates, especially sugary-dense snacks, and low in protein (5). But, where do the changes in diet come from? Factors leading to eat are internal, but also come from external stimuli, such as an abundance of appetizing food, accessibility, stressful situations, good smells, being in a social event, etc., which can lead to overeating. Short sleep has been associated with reduced inhibitory control when it comes to high-calorie foods. A study from 2011 found that specific regions of the brain were highly stimulated in response to unhealthy foods after 5 nights of partial sleep deprivation compared with normal sleep duration in adults (8). Also, alcohol consumption was observed to be higher in adults sleeping less than 6 hours per night (1).
Now, physiologically speaking, what is going when we don't sleep enough? Two main hormones for appetite control and energy balance are affected: leptin and ghrelin. Leptin is known as ''satiety homrone'' as it is secreted when satiety is reached and it inhibits appetite after a meal. On the other hand, ghrelin, known as ''hunger hormone'' is released by the stomach when the body needs a new energy intake, it enhances feeling of hunger. Studies are not consistent about the exact impact of sleep deprivation on these hormones, but alteration of their secretion is definitely observed. In some studies, reduction of leptin was reported, whereas some studies observed an increase with higher levels of ghrelin as well. The underlying mechanism suggested is that an increase in sympathetic nervous system activity in response to sleep restriction inhibits the secretion of leptin and insulin. The sleep restriction would be perceived as a stressor and would induce a '' fight or flight '' response, which decreases several functions linked to energy balance (2). Overall, these findings propose that alteration in these hormones as a result of sleep restriction are associated with increased food intake and weight status (2). Also, in clinical studies, a reduction in glucose tolerance in healthy adults was observed following many nights of 4-5h of sleep (1). Studies suggest that insufficient sleep may be a risk factor for type 2 diabetes (1).
How does our nutrition impact our sleep?
Food for a better sleep
Have you ever heard that a glass of warm milk before bed will help you fall asleep? Some foods contain different nutrients proven to help sleep. Let`s start with melatonin (will discuss melatonin as a supplement later in article). Melatonin can improve sleep efficiency at a certain level. For a long time, it was considered to be exclusively secreted by the pineal gland (only being able to be produced by our body) but melatonin has been found in plants, fungi, insects and bacteria (with no pineal gland) (6). It was observed that eating some food, containing melatonin could assist sleep. Eggs, fish, nuts, some kind of mushrooms, cereals, seeds and germinated legumes are considered to be good dietary sources of melatonin (6). Concentration of melatonin in the serum could increase after the consumption of food containing melatonin.
Another interesting nutrient to promote sleep is tryptophane. Tryptophane is an essential amino acid (a protein building block) which means our body cannot produce it therefore we need to acquire it through food. Tryptophan is converted to 5-HTP (5-hyrdoxytryptophan, will discuss this supplement below), and then to serotonin, melatonin, and vitamin B6 (niacin). It is believed to aid sleep by increased serum levels of melatonin as well as serotonin. Foods containing tryptophan include turkey, chicken, meat, milk, cheese, yogurt, eggs, and fish.
More studies are needed to better understand the role that nutrition can play for sleep. In the meantime, a balanced and diversified diet is the best way to assure a good intake in all micronutrients needed for good health.
Food that disturbs sleep
This one may be the most obvious as limiting coffee or a tea at night is a widely known tip to avoid a bad night of sleep. Caffeine is mainly found in coffee, tea, soft drinks, and chocolate. Indeed, caffeine enhances alertness by acting as an antagonist of adenosine receptors (i.e a stimulant) and therefore reduces inclination to sleep. A review of the effects on sleep came to the conclusion that a strong association exists between caffeine intake during the day and sleep problems (1). In adults, recommendation for caffeine intake is to stay below 400 mg per day (about 2-3 cups of coffee) (13).
Did you ever drink too much wine and fell asleep right away when going to bed? Actually, this gives a false impression that alcohol can help with insomnia. Several studies have looked at the effect of the alcohol intake before bedtime and found that it affects sleep homeostasis and causes sleep disruptions (14). Alcohol might help to fall asleep quicker, but it reduces REM sleep that is known to be the most restorative (14).
Are there supplements to increase sleep quality?
When looking on the Internet what supplements help for a better sleep, a long and variable list is available... but do they really work? Let`s dive deep on some popular supplements advertise to aid sleep: melatonin, magnesium and 5-HTP.
Melatonin is a hormone released by the pineal gland in high concentration in the evening before going to bed and at low concentration during the day. Its principal role is to maintain the sleep-wake rhythm. Melatonin is sold in synthetic form that you can easily find at a drug store and claims to promote sleep. In Canada, more than one hundred melatonin products are licensed as a natural health product (4).
Several studies show that physiological or pharmacologic doses of melatonin help to induce drowsiness and sleep (3). However, limits for generalizing these studies are that different inclusion and exclusion criteria were used, as well as different doses of melatonin and different outcome measures to evaluate insomnia. Meaning, all the different studies use different criteria which makes it hard to compare overall. Nevertheless, some conclusions can still be drawn. A meta-analysis with 17 studies suggested that melatonin reduces sleep onset latency (i.e time fall asleep), enhances sleep efficiency and total sleep duration (3). Melatonin supplements (5-8 mg) have been suggested in regulating sleep patterns in short-term trials (1). It can be useful in the case of jet lag and for shift workers (9). However, in the long term, it's not a solution to improve sleep quality and solve insomnia issues (4). So, melatonin can be effective and safe to use and can help in the short-term, but should not be used as your long term solution to sleep issues.
Magnesium is a mineral that acts as a co-factor for more than 300 enzyme systems and regulates several biochemical reactions in the body. Food sources of magnesium include green leafy vegetables, nuts, whole grain and legumes (10). This mineral has a role in the regulation of central nervous system excitability according to many studies and therefore could play a role in sleep regulation (11).
In a double-blind placebo controlled trial, a 500 mg supplementation of magnesium has been observed to improve insomnia in elderly subjects (11). In this case, elderly adults are more at risk to be in deficiency, which might explain the benefits from the magnesium supplementation. However, studies about dietary magnesium and sleep are limited and it's still unclear if supplementation would be useful for the general population (11). More research is needed for this area.
5-HTP stands for 5-hydroxytryptophan (you don`t need to memorize that!) and it's the intermediate metabolite of amino acid L-tryptophan (as seen above). 5-HTP is implicated in synthesis serotonin, a neurotransmitter involved in the regulation sleep, anxiety and depression. Unfortunately, there are only a few studies investigating the effect of 5-HTP on sleep and they were mainly done on animal models, which can't be generalized to humans. Results of a study from 2016 using a mixture of 5-HTP and GABA suggested that it would improve sleep quality by modulating both GABAergic and serotonergic signalling (12). Again, more studies will help to clarify if 5-HTP supplementation can help for sleep regulation.
MYTHBUSTER: Do not eat 2 h before going to bed.
Really? This is often heard from the diet industry which states that the metabolism slows down before going to sleep and therefore, food will be stored as fat. In the past, it was believed that it was better for body composition (i.e. losing fat) to limit and/or avoid food intake close to bedtime. However, new studies looked at the impact of nutrient intake before sleep and reported positives physiological outcomes. In fact, a review from 2015 found that consuming a small 150 kcal snack rich in protein could improve overnight muscle synthesis, satiety and morning metabolism in healthy men (15). Another study from 2014 indicated that consuming 140 – 150 kcal of protein or carbohydrate before sleep increases satiety and reduces the desire to eat the following morning in sedentary overweight and obese women (16). The issue with late night snacking usually lies withing the food choices we make (like a family size bag of chips with chocolate and wine). Despite differences in studies, it is clear that consuming large amount of food late at night combined with irregular sleep patterns may have adverse health effects. However, if you're hungry, you shouldn't restrict yourself from eating a light snack (15).
Good sleep is a cornerstone for optimal health. Sleep deprivation can have several consequences such as poor concentration, irritability, imbalances in hormones and could also precipitate chronic diseases. A good sleep hygiene, including a balanced diet, no alcohol or caffeine before bed, can help you improve your sleep and give you more energy throughout the day. More research regarding the role of specific foods and supplement will help us better understand the role nutrition can play in sleep management.
My top tips for a better sleep
1- Stop drinking caffeine early afternoon - if you want coffee, choose decaffeinate coffee.
2- Limit alcohol consumption before bed time.
3- Have a consistent bed time (our body LOVES routine- train yourself to go to bed at the same time every night)
4- Turn off electronics at least 1 hour before bed (Reduce stimulation and blue light)
5- Stop drinking water 1-2 h before bed (especially for my friends with small bladders- less disruption = better sleep)
6- If hungry, have balanced night time snack (protein+complexe carbohydrates) and avoid going to bed hungry
I hope this article was helpful! On this note, Good night!
Questions? Comments? Don't hesitate to reach out!
Marie-Pier Pitre-D'Iorio, RD, B.Sc.Psychology
A BIG thank you to Myriam Beaudry for this article.
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