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Hello. Many of you have probably experienced feeling sleepy after lunch, such as during meetings.
Some of you may have even succumbed to the drowsiness and ended up taking a nap.
In this article, I would like to introduce ways to combat that afternoon drowsiness and the struggle against sleep pressure.
What to do when you feel sleepy
Drowsiness means that alertness is weakening and you are leaning towards sleep. To overcome this drowsiness, you must intentionally activate your alertness switch.
Stimulating yourself or consuming awakening ingredients can be effective. I will introduce specific methods below.
Ingesting awakening ingredients
You might see people with gum at their desks, and it can be said that chewing gum when you feel sleepy or need to concentrate is effective. Chewing refreshing mint or caffeinated gum provides both "ingestion of awakening ingredients" and "stimulation from chewing (exercise)".
Regarding stimulation from chewing, though it might not be appropriate for office settings during the day, eating chewy foods like dried squid or hard senbei crackers can transmit stimulation to the brain via the ascending branches of the trigeminal nerve.
According to a survey by the Japan Chewing Gum Association, which measured the number of chews per 10g of edible portion, gum is chewed approximately 550 times before being discarded, resulting in an overwhelmingly higher number of chews compared to other foods (*1).
As for ingesting awakening ingredients, consuming caffeine, the most widely consumed stimulant substance in the world, is effective.
While caffeine might bring coffee to mind, it is also found in energy drinks, soft drinks like cola, green tea, hojicha (roasted green tea), and black tea, in addition to coffee. It is also present in chocolate and cocoa made from cacao beans.
Source: Ministry of Agriculture, Forestry and Fisheries, Regarding excessive caffeine intake
Furthermore, the temperature of your drink is also important in terms of contributing to alertness.
Although cold drinks might seem more awakening, experimental results show that, similar to warm soup at breakfast, slightly raising core body temperature with warm drinks is effective for alertness, making warm drinks more appropriate. This is because alertness requires a relatively high core body temperature (the difference between core and skin temperature).
Caution advised for excessive caffeine intake
The Ministry of Health, Labour and Welfare reports that while moderate caffeine intake can have effects such as alertness, vasodilation, and cancer suppression, excessive intake can lead to increased heart rate, arrhythmia, excitement, anxiety, tremors, dizziness, insomnia, diarrhea, and an increased risk of high blood pressure (with long-term intake).
It is also reported that children, pregnant women, breastfeeding women, and individuals highly sensitive to caffeine experience greater adverse health effects, and therefore, various countries set lower upper intake limits than for adults (*2).
According to the World Health Organization (WHO), the upper limit for coffee intake for pregnant women should be 3-4 cups per day (*3). Please consume within appropriate limits.
Providing stimulation
When you feel sleepy, have you ever applied a cold plastic bottle to your face or neck, and the sudden coolness woke you up?
While there is still limited scientific evidence, it is theoretically sound, so lowering skin temperature and applying stimulation may be an effective way to combat drowsiness and refresh oneself.
For example, if you're sedentary at a desk, it would be effective to take a short walk or stretch, wash your face with cold water, wipe your body with a cool sweat-wiping sheet, lightly pat your cheeks or feet, or step outside into the cold air from a warm room in winter.
Furthermore, in the sports field, cooling has been confirmed to be effective in fatigue recovery and improving athletic performance. Some American football teams are already applying and utilizing this. While its application and utilization in sports and medicine are still evolving, various initiatives and services are expected to emerge in the future.
Reasons for daytime drowsiness
When considering why we feel sleepy in the afternoon, we tend to associate it with lunch, but it turns out that there isn't much connection. Multiple studies have shown experimental results indicating that "lunch itself is not related to the shortening of sleep latency (onset of drowsiness) that occurs around 2 PM," leading to the conclusion that lunch is not the primary biological cause of afternoon drowsiness.
Additionally, there is a theory that "when you eat, more blood is used for digestion and absorption by internal organs, reducing blood flow to the brain, which makes you feel sleepy." However, blood is preferentially directed to the brain in any situation, so this theory is also incorrect.
However, even if there is no change in blood flow to the brain, excessive lunch intake might lead to feeling "sleepy because the feeling of fullness reduces motivation, making you feel disinclined to do anything."
Feeling sleepy around 2 PM is called the "afternoon dip" in Western countries and is considered more of a circadian rhythm issue. Regardless of whether you eat lunch or not, this time of day is when alertness tends to naturally decrease slightly.
Since monkeys often nap during this time, this daytime drowsiness, influenced by circadian rhythms, might be a remnant of our phylogeny.
Many researchers have conducted experiments on the mechanism and countermeasures for the "afternoon dip," but they consistently show results such as:
- (1) Drowsiness occurs during this time even if lunch is skipped
- (2) Drowsiness is reduced by caffeine intake (e.g., coffee)
- (3) Chronic sleep deprivation exacerbates drowsiness
Personally, no matter how much breakfast I eat, I don't feel sleepy afterwards, so I believe the influence of circadian rhythm is indeed significant for the "afternoon dip."
Fundamental countermeasures
Resolving sleep debt and adjusting your schedule (individual)
If you usually wake up with difficulty and often feel sleepy during the day, it's a sign that you have accumulated sleep debt.
In such cases, chewing gum, touching something cold, or taking a nap may provide temporary relief, but it won't offer a fundamental solution.
The cause is a disrupted sleep rhythm or insufficient sleep duration and quality. Therefore, for a long-term approach, it is advisable to first review your own sleep habits.
Also, if you frequently feel sleepy around 2 PM, it is effective to adjust your schedule and manage tasks by not performing important tasks during that time (doing important tasks when you can concentrate) or by taking a short nap.
Adjust what you can adjust to improve your own performance.
I recommend trying to increase your daily sleep time, even by just 15 or 30 minutes, to see if your drowsiness and performance improve.
Many people are unaware of sleep deprivation due to habit, but a common characteristic is that many become aware of it when they improve their sleep.
Improving the working environment and changing meeting styles (organization)
In addition to individual efforts, company (organizational) efforts are also important.
For example, regarding meetings, meeting times in Japan are significantly longer compared to overseas, and the format is often one-sided speeches by specific individuals rather than discussions.
Our attention spans are not that long to begin with.
While there are significant individual differences, the maximum duration is said to be about two hours (children generally have shorter attention spans than adults).
A survey conducted by Benesse targeting junior high school students on sleep duration and learning effectiveness showed that learning in multiple short sessions (15 minutes x 3 sets) was more effective for learning retention and concentration than long sessions (60 minutes) (*9).
Also, speaking and standing up stimulate the brain.
Therefore, by setting shorter meeting times (and providing frequent breaks for longer meetings), holding standing meetings, and using meeting formats that encourage active participation, drowsiness can be alleviated, concentration can be maintained at a certain level or higher, and meeting productivity can be increased.
Furthermore, workplaces with chronically long overtime hours may be cutting into individuals' sleep time due to extended work hours.
In such cases, since the brain and body are not in optimal condition, overall organizational productivity tends to decrease. Improving management systems for tasks and resources is also considered effective.
【References】
※1: Does Chewing Also Affect Memory? - Surprising Effects and Benefits of Chewing
※2: Ministry of Agriculture, Forestry and Fisheries, Food Safety Policy Division, Consumer Affairs and Food Safety Bureau, Regarding Excessive Caffeine Intake
※3: WHO, Healthy Eating during Pregnancy and Breastfeeding, Booklet for mothers, 2001
