For Those Who Can't Fall Asleep for Over 30 Minutes After Getting Into Bed | The Truth About Sleep-Onset Insomnia and How to Deal With It - Nutritional Strategies for 'Sleep'
You can't sleep for some reason. It's not that your mind is wide awake, and your bedtime hasn't changed significantly from usual. Yet, you still can't seem to fall asleep. Have you ever experienced that?
In fact, this type of insomnia is surprisingly common.
That might be due to your core body temperature.
Sleep is not simply a 'phenomenon that occurs because you are tired.' The human body has physiological conditions for falling asleep, and one of them is core body temperature.
[For those who feel they have issues with sleep]
We introduce type-specific diagnoses and recommended ingredients. Please try to find the nutritional strategy that suits your type here.
Core body temperature refers to the temperature of the central part of the body, such as the brain and internal organs. This temperature changes throughout the day and has a rhythm of being high during the day and low at night.
This is the important part.
People feel sleepy when their body temperature drops.
At night, the body begins to prepare for sleep. The thermoregulatory center in the hypothalamus activates, blood vessels in the hands and feet dilate, and heat is released from the skin. As a result, the core body temperature slowly drops, and the brain enters sleep mode.
Conversely, if the core body temperature does not drop sufficiently, the brain still recognizes it as 'active time.' As a result,
sleep onset is delayed
drowsiness does not occur
sleep becomes shallow
and other such problems occur.
The cause of not being able to sleep is often not the 'brain' but the 'body temperature.'
This relationship has been repeatedly confirmed in sleep research.
For example, one study often cited in the field of sleep research is by Krauchi et al. (1999). This study examined in detail the relationship between pre-sleep temperature changes and the onset of sleep. As a result, it was shown that the timing of sleep onset is strongly associated with a drop in core body temperature. In particular, it has been confirmed that the more the skin temperature of the hands and feet rises and heat is released from the body, the shorter the time until sleep onset becomes.
Also, a study by Raymann et al. (2005) verified the relationship between core body temperature and sleep onset. In this study, after investigating the relationship between thermoregulation and sleep, it was shown that when the drop in core body temperature is insufficient, sleep latency (the time it takes to fall asleep) becomes longer. In other words, when body temperature is high, the brain is in a state where it is difficult to enter sleep.
Sleep onset occurs not because 'the brain is tired,' but because 'the body temperature has dropped.'
For this reason, controlling core body temperature is a very important factor when considering the quality of sleep. Just like stress and the biological clock, thermoregulation is also an important part of the physiology of sleep. From the next chapter, I will introduce how to adjust core body temperature from the perspective of nutritional strategy.
Sleep is not disrupted by a single cause. I have summarized nutritional strategies for those with various sleep concerns in the article below, so please take a look.
Chapter 1: Glycine - An Amino Acid That Supports the Reduction of Core Body Temperature
In the previous chapter, I explained that a reduction in core body temperature is necessary for falling asleep. So, can this drop in body temperature be supported from a nutritional perspective?
The representative nutrient for this is glycine.
Glycine is one of the amino acids with the simplest structure present in the body, and it is widely known as a component that makes up proteins such as collagen. It is also contained in many foods and is abundant in meat, fish, and gelatin.
Nutritionally, glycine is classified as a non-essential amino acid. In other words, it is an amino acid that the body can synthesize itself, but it is known to be highly safe even when ingested through food or supplements. In fact, it has long been used as a food additive and is a relatively easy-to-handle ingredient in terms of safety.
Glycine is a highly safe amino acid that is also widely used as a food ingredient.
Why does glycine lower core body temperature?
The reason glycine is related to sleep lies in its effect on body temperature regulation.
It is believed that after ingestion, glycine reaches the brain through the bloodstream and acts on the thermoregulatory center of the hypothalamus. As a result, it has been reported that peripheral blood vessels dilate, promoting heat dissipation from the skin of the hands and feet.
The changes that occur in the body can be visualized as follows:
Peripheral vasodilation
↓
Increase in skin temperature
↓
Increased heat dissipation
↓
Decrease in core body temperature
In other words, rather than directly lowering body temperature, glycine is thought to 'help lower core body temperature by promoting heat dissipation.'
Glycine promotes heat dissipation and supports the drop in body temperature necessary for sleep.
This action may lead to easier sleep onset and improved sleep quality.
Clinical research on glycine and sleep
Regarding the effects of glycine on sleep, multiple clinical studies have been conducted by Japanese research groups.
For example, a study by Yamadera et al. (2007) investigated the effects of glycine ingestion before bedtime on adults dissatisfied with their sleep quality. As a result, the group that ingested glycine showed improvements in subjective sleep quality and ease of falling asleep. Additionally, reductions in fatigue the following day and improvements in daytime performance have been reported.
Furthermore, a study by Inagawa et al. (2006) examined the relationship between body temperature changes after glycine ingestion and sleep. In this study, when glycine was ingested before bedtime, peripheral skin temperature increased and a tendency for core body temperature to decrease was observed. It was suggested that this change in body temperature might be associated with a reduction in sleep latency.
Glycine may promote a decrease in core body temperature and support sleep onset.
In this way, glycine is not a raw material that sedates the nerves like a sleeping pill, but rather is characterized by the fact that it acts on sleep through the physiological mechanism of body temperature regulation.
Glycine Dosage and Timing
Regarding the dosage of glycine, the amount used in Japanese Foods with Function Claims serves as a reference. Many products use approximately 3g of glycine per day.
In research as well, the effect on sleep is often examined at a dosage of around 3g, and this amount is considered a practical guideline. Also, as for the timing of intake,
30 to 60 minutes before bedtime is often used. This takes into account the time it takes for glycine to act on body temperature regulation.
Please try taking about 3g of glycine per day, 30-60 minutes before bedtime.
Since a drop in core body temperature acts as a trigger for falling asleep, taking glycine before bedtime may help support the process of lowering body temperature.
Chapter 2: Nutritional Strategies to Regulate Core Body Temperature
Core body temperature is an indicator that is difficult to be conscious of on your own. Because it is not something you can feel like heart rate or fatigue, you rarely notice it in your daily life.
However, in reality, it is one of the important physiological indicators that determine the quality of sleep.
Core body temperature is one of the physiological switches that determine whether or not you can sleep.
When body temperature drops sufficiently, the brain enters sleep mode; conversely, when body temperature is high, the brain recognizes that it is still time to be active. Therefore, if the drop in core body temperature does not occur properly, problems may manifest in the form of not feeling sleepy or being unable to fall asleep.
The important point is that with this type of insomnia, stress or nervous excitement is not necessarily the cause. For example,
not feeling strong stress
bedtime does not change significantly every day
not feeling like your head is clear
Even so, for some reason you cannot fall asleep. In such cases, it is worth suspecting the rhythm of your core body temperature.
If you cannot sleep even though there are no problems with stress, arousal, or your internal clock, body temperature regulation may be involved.
Sleep is not determined by a single factor, but is established by a combination of multiple physiological systems such as nerves, hormones, body temperature, and the internal clock. Among these, body temperature regulation is a relatively overlooked element, but in reality, it has an important role as a trigger for falling asleep.
Like the glycine introduced this time, there are also nutritional approaches that support sleep from the perspective of body temperature regulation. When considering sleep problems, it is important not to simply look for 'ingredients that make you sleepy,' but to think about which physiological elements are disrupted.
The effectiveness of sleep supplements changes depending on 'choosing them according to the cause'.
In this note, I share information based on the theme of nutritional strategies for professionals to consistently perform at a high level. Sleep is, after all, the foundation of your daily condition, concentration, and recovery. My goal is to organize information about sleep based on physiology and research data.
Please let me know in the comments if there are any topics you are interested in.
If there are any topics or specific areas you would like me to cover in the future, please let me know in the comments. It can be a general topic or a specific ingredient. I will use your feedback as a reference for my future work!
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Wishing you all good health ✋
[For those who feel they have issues with sleep]
I introduce type-specific diagnoses and recommended ingredients. Please try finding a nutritional strategy that suits your type here.