Sleep and how to sleep well

Sleep

Sleep is increasingly recognized as a critical component of healthy development and overall health, and is essential for maintaining immune health, restoring energy and memory consolidation, while not sleeping is a risk factor for a variety of significant health problems, such as cardiovascular disease, diabetes, obesity, as well as bad mood and cognitive dysfunction.

In general, there is no magic number or ideal amount of sleep to get each night that could apply broadly to all. The optimal amount of sleep should be individualized, as it depends on many factors  —  a complex interplay between genetic, behavioral, environmental and social factors  —  with the average sleep time among humans varying between 5hrs to 10hrs:Sleep the shutting of the eye: sleep duration and genes.

Sleep has been a subject of intense interest to poets and mystics since ancient times, and 2000 years ago Plutarch quoted: “All men whilst they are awake are in one common world: but each of them, when he is asleep, is in a world of his own”.

But it was only in the last 70 years that scientists and physicians attempted a systematic study of the biology and disorders of sleep.

As a matter of fact, it was the electroencephalogram (EEG) invention that allowed scientists to study sleep in ways that were not previously possible. An EEG is a measurement of the continuous electrical activity of the brain, detected via small metal discs called electrodes that are positioned in standardized patterns on the scalp and used to monitor brain activity.

It all started during the 1950s, when a graduate student named Eugene Aserinsky, used EEG to discover what is known today as REM sleep. Later, further studies of human sleep have demonstrated that sleep progresses through a series of stages in which different brain wave patterns are displayed.

Based on this wave patterns today we know that there are two main types of sleep:

1. Non-rapid eye movement (NREM)  —  also known as quiet sleep (stage N1, N2, N3), and
2. Rapid eye movement (REM)  —  also known as active sleep or paradoxical sleep (stage N4).

Very briefly, stage N1 sleep is the change over from wakefulness to sleep. Stage N2 sleep is a period of light sleep before you enter deeper sleep. Stage N3 sleep is the period of deep sleep that you need to feel refreshed in the morning. REM sleep, also known as paradoxical sleep, first occurs about 90 minutes after falling asleep. Most of your dreaming (or nightmares) occurs during REM sleep, when your eyes move rapidly from side to side behind closed eyelids and your arm and leg muscles become temporarily paralyzed, which prevents you from acting out your dreams. The sleep cycle of alternate NREM and REM sleep, takes an average of 90 minutes, occurring 4–6 times in a good night’s sleep.

But what regulates your sleep-wake cycles?

Well, you have two internal biological mechanisms that regulate your sleep-wake cycles:

1. the circadian rhythm (your genes and your internal clocks or Circadian Clock Genes) and
2. the sleep-wake homeostasis.

But what is this sleep-wake homeostasis or homeostatic regulatory capacity?

Your sleep-wake homeostasis is just a mechanism that keeps track of your need for sleep. The circadian modulation (internal clocks and genes), makes you go to bed at night and makes you wake up in the morning. But when sleep is lost, this loss is compensated by the homeostatic regulatory aspect of our sleep, a process thought to be one of the main regulatory processes in sleep and seems to be universal, as it is found in many different phyla of the animal kingdom.

In other words, if you haven’t slept well during the night your homeostatic regulatory aspect of your sleep will find a way to compensate for this lost. How? For example by telling you to take a nap during the day.

Both homeostatic and circadian processes are acting downstream on physiology and behaviour. And there is limited evidence that the central circadian pacemaker is influencing sleep homeostasis.

However, there is more evidence of sleep homeostatic mechanisms influencing functioning of the circadian clock. The latter can be applied to optimize shift work protocols and recovery from jet-lag: Sleep homeostasis and the circadian clock: Do the circadian pacemaker and the sleep homeostat influence each other’s functioning?.

Your homeostatic sleep drive reminds your body to sleep after a certain time and regulates sleep intensity. This sleep drive gets stronger every hour you are awake and causes you to sleep longer and more deeply after a period of sleep deprivation.

The factors that influence your homeostatic process include:

1. medical conditions,
2. medications,
3. stress,
4. sleep environment,
5. exposure to light,and
6. what you eat and drink.

But today we are going to see how your diet can affect your sleep-wake homeostasis.

Diet and sleep

This narrative review (Effects of Diet on Sleep: A Narrative Review) published on March 2020, searched for sleep and diet research conducted on healthy adults (clinical studies). The source articles were identified using the online databases Cochrane, PubMed, and Cumulative Index of Nursing and Allied Health Literature (CINAHL), and were searched from 1990 to August 2019 for eligible studies. Initially 3545 articles were identified, but after excluding 3512 articles, 32 articles that met the inclusion criteria remained and were included in the final review.

A narrative analysis of these studies revealed four key themes that affect sleep: tryptophan consumption/depletion, dietary supplements, food items, and macronutrients.

Tryptophan

The effects of either tryptophan consumption or acute tryptophan depletion on sleep was investigated in five studies in this review, and tryptophan-containing foods improved sleep compared with controls .

In particular, an increase in total sleep time, sleep efficiency, and immobile time was noted after a week of tryptophan-rich (60 mg) cereal consumption in older adults, while participants in this study also experienced less difficulty in falling asleep, less waking at night and less fragmented sleep. Similar improvements in sleep were noted in another study of middle-aged adults after 19 days of tryptophan-rich (70 mg) egg-white protein hydrolysate formulation consumption.

Tryptophan is an essential amino acid in humans, requiring that it be ingested since it cannot be made. When in the brain, it is converted to serotonin, the precursor to the sleep-promoting hormone melatonin (an hormone made by the pineal gland, that helps your body know when it’s time to sleep and wake up). In fact, also consuming foods containing high concentrations of melatonin and serotonin (e.g., cherries) is associated with improvements in sleep duration and quality.

On the other hand, reducing the availability of tryptophan prevents the synthesis of serotonin and subsequently reduces sleep quality.

In fact, it has been reported (three studies) that significant reduction in total sleep time, sleep efficiency and time spent in stage N2 occurs after drinking a 100% tryptophan-free drink, compared with a 25% tryptophan-free drink.

Dietary Supplements

Thirteen studies were identified investigating the effect of consuming dietary supplements on sleep. Zinc is necessary in the metabolism of melatonin and is one of the three minerals that have a sedative effect on the nervous system (the others are calcium and magnesium) and is also thought to help mental recovery post-stress.

In one study zinc supplementation in individuals with below-optimal zinc levels (≤ 79.9μg/dL) was studied, and improvements in sleep quality and sleep onset latency scores were recorded. A separate study, which administered astaxanthin (a keto-carotenoid) in combination with zinc, observed a significant improvement in sleep onset latency, but no effects on total sleep time or sleep efficiency.

The effect of a blend of polyphenol compounds was also studied on sleep quality (HolisFiit consists of flavonoids, as well as natural caffeine and vitamin B3). Compared to the placebo group, those ingesting HolisFiit reported lower sleep disturbances, and greater total sleep duration and sleep quality at the end of 16 weeks of supplementation.

It was found that a group of poor sleepers who were administered phlorotannin (a supplement derived from brown seaweed) experienced decreased waking after sleep onset and total wake time compared with those administered the placebo.

The potential sleep-promoting benefit of phlorotannins has been identified through their ability to bind to GABA-benzodiazepine receptor sites, which may assist in obtaining adequate sleep, since GABA is associated with sleep regulation. GABA is the main inhibitory neurotransmitter of the central nervous system. It is well established that activation of GABA receptors favors sleep.

Two studies examined crocetin (a carotenoid compound) supplementation on sleep, and significantly fewer waking episodes were recorded. Moreover, participants reported feeling refreshed, and had less sleepiness upon waking, following crocetin administration.

Another study examined the effect of chlorogenic acids (CGA) — derived from green coffee beans. Participants who consumed CGA experienced shortened sleep onset latency and higher delta power in the first hour of sleep compared with controls, demonstrating a potential benefit of CGA for sleep quality.

Moreover, consuming a Chlorophytum borivilianum and velvet bean supplement indicated a reduced sleep onset latency as well as improved sleep quality scores, sleep duration, habitual sleep efficiency (the ratio of sleep time to total time in bed) and sleep disturbance scores, compared to those that did not consume the supplement. And an increase of growth hormone (GH) post-consumption was observed. GH is naturally released when the body is promoting sleepiness.

The amino acid, γ-aminobutyric acid (GABA), and Apocynum venetum (herb) leaf extract (AVLE) were also examined both separately and in combination to identify changes in sleep indices. GABA significantly reduced sleep onset latency, while AVLE increased non-REM sleep time, although minimal effects of AVLE were observed on delta waves. The combination of these ingredients did not provide a synergistic effect.

Food items

One study investigated the sleep-promoting effects of consuming different cultivars of Jerte Valley cherries (sourced from Spain) in middle-aged and elderly individuals.

In general, significant improvements were found in middle-aged participants for total sleep time, sleep efficiency, the number of awakenings, total nocturnal activity, assumed sleep, and sleep onset latency. Additionally, older adults experienced decreases in the number of awakenings, immobility, and sleep onset latency, and increases in assumed sleep.

In a later study, the impact of consuming a Jerte Valley product containing four combined cultivars of cherries was explored in young, middle-aged, and elderly participants compared with placebo controls. The greater improvement was identified in the middle-aged and elderly groups. In another separate study investigating the consumption of Montmorency tart cherry juice the participants spent less time napping and more time sleeping, and had higher total sleep efficiency scores compared with baseline and placebo.

As already mentioned cherries contain high concentrations of melatonin and serotonin, which are associated with improvements in sleep duration and quality.

One study has also examined the effect of consuming seafood on sleep outcomes, where consuming zinc-rich oysters and astaxanthin-containing krill resulted in improved sleep quality. Astaxanthin is an aquatic carotenoid pigment that occurs in trout, microalgae, yeast, and shrimp, among other sea creatures. It’s most commonly found in Pacific salmon and is what gives the fish its pinkish color.

Macronutrients

Ten studies investigated the effects of manipulating the macronutrient content of dietary intake on sleep outcomes.

In one study, healthy men experienced a shortened sleep onset latency when they were provided with a high glycemic index (GI) meal that was consumed four hours before bedtime. High glycemic index (GI of 70 or higher) means: white bread, rice cakes, most crackers, bagels, cakes, doughnuts, croissants and most packaged breakfast cereals. And in a separate study, reduced sleep onset latency was observed following the consumption of a high CHO diet over a four-day period.

High CHO meals can increase the tryptophan to LNAA ratio. An increase of plasma glucose drives insulin secretion and the consequent removal of circulating LNAAs. Tryptophan is excluded from this process, therefore leaving it in a favourable position to cross the blood-brain barrier and consequently convert into serotonin. This could also partly explain consistent findings for improved sleep following the ingestion of high CHO meals in the current review, though these studies did not directly examine the mechanism.

Two studies explored the effects of ketosis (a physiological state induced by a diet typically characterised by a low CHO and high fat intake). Ketosis is a natural metabolic state. It involves the body producing ketone bodies out of fat, and using them for energy instead of carbs. To go into ketosis, people generally need to eat fewer than 50 grams of carbs per day and sometimes as little as 20 grams per day. This requires removing certain food items from your diet, such as grains, candy and sugary soft drinks. You also have to cut back on legumes, potatoes and fruit.

One study found that sleep parameters did not differ between the ketosis phases of a very low CHO, high fat, and high protein diet and placebo. However, increases in the percentage of N3 and decreases in the percentage of REM sleep were observed following ketosis compared with control.

In a separate study involving the provision of a very low calorie, ketogenic diet to obese participants for four months, an improvement in subjective sleepiness was observed during the reduced ketosis phase; however, no changes in other self-reported sleep quality measures were identified.

Overall, the collective studies included in this review suggested that the consumption of certain nutrients (tryptophan), food items (cherries), and dietary supplements (zinc), and manipulating some dietary components (macronutrient and energy composition) can influence (i.e., disrupt or improve) sleep outcomes.

So, whatever the reason for your sleep loss is — work, babies, worry, parties or late night television — remember...all you need is sleep promoting food!

Thank you for reading 💙

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In winter I get up at night And dress by yellow candle-light. In summer, quite the other way, I have to go to bed by day. — By Robert Louis Stevenson