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Many people know that sleep and caffeine are closely related. Many of you probably drink coffee in the morning to remove drowsiness and use its effects, or avoid coffee before bed and relax by drinking warm herbal tea.
However, it is said that many people do not know the effects of caffeine on sleep, drink coffee every night before bed, and suffer from chronic sleep deprivation and insomnia. To resolve these problems, it is best to understand how caffeine affects your body.
This article will introduce the caffeine content of various beverages and recommended drinks before bedtime. Take this opportunity to learn about the relationship between caffeine and sleep and create good sleep habits!
1. Why can't I sleep if I consume caffeine before bed?
It is well known that consuming caffeinated tea or coffee before bed awakens the brain, making it difficult to fall asleep, and that a shorter sleep duration affects your awakening the next day. Drinking tea or coffee at night can lead to insomnia and lack of sleep.
The mechanism that inhibits drowsiness is largely influenced by the relationship between caffeine, which causes excitation, and adenosine, a sleep-inducing substance. Normally, adenosine suppresses histamine, an arousal substance, and increases the desire to sleep.
However, caffeine blocks adenosine receptors in the ventrolateral preoptic nucleus of the hypothalamus, making it easier for histamine, an arousal substance, to be released, which awakens the brain and makes it difficult to fall asleep. Adenosine, which promotes sleep, is like an owner who wants to close their store early, and caffeine before bed is like a troublesome customer right before closing. The store is ready to close, but it can't because there are customers.
1-1. Caffeine has an awakening effect
Many people have a negative impression of caffeine, having heard stories of caffeine poisoning from drinking too much coffee or energy drinks.
The effects of caffeine vary from person to person, but it can positively activate brain activity and improve work performance after a nap. This is because caffeine has a strong awakening effect that suppresses drowsiness.
Many people probably have a habit of drinking a cup of coffee in the morning to shake off sleepiness. This is exactly one of the awakening effects. Incorporating coffee into your daily life can provide many benefits.
In particular, utilizing the stimulating effect can help improve attention and concentration at work. Other effects include promoting metabolism and blood circulation, which can aid in weight loss and improve athletic performance, leading to the excretion of waste products and increased metabolism, among other things!
Caffeine can also be a powerful partner in building a healthy body every day, so take this opportunity to make caffeine your ally.
1-2. How caffeine actually affects sleep
Is it true that drinking coffee before bed makes it difficult to sleep? There was an experiment that investigated caffeine intake before bed to find out whether drinking a cup of coffee after work and relaxing affects sleep. *1
In an experiment conducted at Henry Ford Hospital in Detroit with multiple subjects, caffeine was administered at three different times (immediately before bed, 3 hours before bed, and 6 hours before bed). The results showed that it had a significant impact on sleep onset and sleep depth.
In this experiment, a large amount of caffeine (400 mg) was administered, so the situation is different from real-life scenarios, but the results showed that caffeine intake 6 hours before bed still affected sleep.
In other words, consuming caffeinated beverages or foods before bedtime has some negative effects on the body, disrupting the sleep cycle and leading to sleep deprivation and insomnia.
2. Should I absolutely not drink coffee before bed?
From what we've discussed so far, many of you may have gotten the impression that coffee contains caffeine and can interfere with sleep, so it's healthier not to drink it at all before bed.
However, coffee also has relaxing effects, can improve sleep performance, and makes you wake up refreshed in the morning.
You might think, "Wait, didn't you just say that coffee has an excitatory effect due to caffeine?" and that it sounds contradictory. However, research has proven that the aroma of coffee acts on the brain, increases alpha waves, and provides a relaxing effect. *2
So, what should you do? Instead of drinking coffee, it's good to put coffee beans in your bedroom and enjoy the aroma. This can lead to fatigue recovery, muscle fatigue relief, and a better morning awakening.
2-1. Depending on the timing, you might wake up feeling better.
Have you ever heard that drinking a cup of tea or canned coffee before a short nap makes you feel refreshed when you wake up?
That's because caffeine takes effect about 30 minutes after ingestion, and it improves attention and concentration, which are important for work performance after sleep.
When you're hit by sleepiness after lunch and can't get any work done, you might be told, "Why don't you take a 15-20 minute nap?" At this time, by consuming a caffeinated beverage and then taking a nap, the awakening effect will appear when you wake up, and you can eliminate sluggishness and drowsiness.
To regain concentration and boost productivity in the afternoon, try combining caffeine intake with a nap.
2-2. Be mindful of when you consume caffeine.
The timing of caffeine-containing beverage consumption changes its effect on daily performance and sleep.
It is no exaggeration to say that how much physical and mental fatigue can be recovered through sleep depends on whether deep sleep can be achieved. To achieve deep sleep, it is necessary to consciously change pre-sleep habits.
It is sometimes said that caffeine's effects last for 5 to 8 hours, and it takes several days for it to be completely eliminated from the body. Consuming caffeine from coffee or other sources in the morning or daytime can awaken the brain and improve efficiency, so rather than completely eliminating caffeine from your life, it is important to adjust the timing of caffeine intake and use it wisely.
The half-life of caffeine is said to be 4 hours, so it is important to avoid consuming caffeinated beverages such as coffee at least 4 hours before bedtime to improve sleep quality.
While sleep duration varies from person to person, one method is to set a "curfew" for when you consume caffeine from coffee, tea, chocolate, etc. For example, you could set 6 PM as the curfew, and allow yourself to have coffee, tea, or chocolate until then.
Simply stopping caffeine intake in the evening can change your sleep quality.
Many people have experienced significant improvements, such as "no longer waking up in the middle of the night and improved insomnia," simply by stopping caffeine intake at night.
3. What is the appropriate timing and amount of caffeine to consume?
Caffeine intake significantly affects internal rhythms and daily life. Knowing how much to consume at the appropriate time to boost daytime performance and achieve restful sleep is a significant advantage.
Caffeine has beneficial effects such as waking you up and relieving fatigue, and it is found in large amounts in coffee, tea, and energy drinks, including energy drinks. One cup of coffee contains 100-120mg of caffeine. The maximum recommended daily intake of caffeine is 300-400mg.
Since you can drink about 2-3 cups of coffee a day, it's appropriate to have about one cup in the morning and one at noon. We must not forget that excessive intake can lead to caffeine poisoning, addiction, and gastrointestinal disorders, causing physical discomfort.
First, please understand the effects and disadvantages it has on your body, and then understand the appropriate timing and amount.
3-1. Absolutely no caffeine 4 hours before bedtime.
The half-life of caffeine is about 4 hours, and its effects last for 5 to 8 hours in the body after ingestion, so setting a coffee curfew 8 hours before bed is ideal.
For example, if you always go to bed at 10 PM, simply limiting your coffee and energy drink intake until 2 PM will improve your sleep quality.
However, for those who absolutely want to warm their bodies with tea before bed to fall asleep, it's a good idea to drink decaffeinated coffee (decaf) or caffeine-free herbal tea. Caffeine-free rooibos tea is also recommended.
Additionally, individuals with high sensitivity due to age or body type, or older adults who tend to have lighter sleep, should avoid caffeine intake as much as possible after the evening.
3-2. Aim for a daily caffeine intake of 400mg or less.
As mentioned earlier, the recommended daily caffeine intake is 300-400mg. The caffeine content varies not only in coffee but also in tea and energy drinks like Red Bull.
Recently, non-caffeinated beverages are also sold in convenience stores and supermarkets. "But there are individual differences, and aren't there different guidelines for men, women, pregnant women, and children?"
Basically, daily intake below the caffeine tolerance limit is not a problem, but the guideline for men is 400mg, and for women, it is 300mg as it can affect menstruation. *3
- Men: 400mg
- Women: 300mg
- Pregnant women: 200mg
Generally, one mug (150-200ml) of coffee contains about 100-120mg, so 1-2 cups per day is appropriate. It is also known that some people have allergic reactions to caffeine, so if you drink a caffeinated beverage and feel unwell, stop consuming caffeine and observe if your condition improves.
4. How much caffeine is actually in drinks?
When you hear "caffeine," you might typically imagine coffee. In reality, caffeine is found in oolong tea, cocoa, green tea, black tea, and foods like chocolate.
While strong caffeine-concentrated energy drinks are sold, many convenience stores also offer non-caffeinated tea and other bottled products, offering consumers a wide range of choices. The caffeine content varies by beverage type, so let's check how much caffeine is actually in each drink.
[Main caffeine content and approximate caffeine concentration]*4
| Beverage Name | Caffeine Concentration |
|---|---|
| Coffee | 60mg/100ml |
| Instant Coffee | 57mg/100ml |
| Oolong Tea | 20mg/100/ml |
| Black Tea | 30mg/100ml |
| Gyokuro | 160mg/100ml |
| Sencha | 20mg/100ml |
| Energy Drink | 36~150mg/bottle |
Among common beverages, coffee contains the most caffeine, but be aware that some energy drinks and canned coffees have high caffeine content depending on the type.
Recently, bottled teas like "Catechin Green Tea" and "Strong Green Tea" are available in a wide variety of flavors, from regular to richer ones. The caffeine content is also displayed, so we recommend being mindful of it when purchasing at convenience stores or supermarkets.
5. Recommended drinks before sleep
Drinking coffee, which contains a lot of caffeine, is not recommended before bed. However, some people might want to know if there are any recommended drinks that can warm their bodies and improve sleep quality before bed.
Before bedtime, it's good to warm up milk to make hot milk, or try caffeine-free herbal teas or rooibos tea. Here are some recommendations: [Recommended drinks and their effects]
- Herbal tea: Healing and calming effects from its aroma
- Ginger tea: Warms the body from within, soothes menstrual pain
- Hot water: Relaxing effect
- Hot milk: Regulates the autonomic nervous system for good sleep
- Soy milk: Improves skin and aids fatigue recovery
Avoid coffee, black tea, and energy drinks. These have strong stimulating effects. Aim to drink ginger tea or hot milk, which regulate your body from within, about an hour before bedtime, and take your time to drink it slowly.
This is also called "sleep ritual," and a habit of slowly drinking a warm beverage before bed can lead to good sleep.
Furthermore, by doing slow stretches and loosening your body before bed, your muscles will relax, and it is expected to promote restful sleep and fatigue recovery.
Summary: Understand the effects of caffeine to create a sleep-wake rhythm
We hope you now understand that sleep and caffeine are closely related. You also learned why the cup of coffee you drink every morning to wake up is good!
If you have trouble falling asleep at night or waking up in the morning, the cause might be your pre-sleep drinking habits. Please review them. Key points this time:
- Caffeine's awakening effect can be utilized for power naps or daytime naps.
- Set a caffeine curfew (e.g., no coffee after 6 PM).
- Limit daily intake to 300-400mg (up to 2 cups of coffee).
- Avoid caffeine as much as possible 4 hours before bedtime.
- Drink hot milk or rooibos tea before bed.
Caffeine, when consumed at the right time, can have many benefits, such as positively impacting work performance and aiding in exercise and weight loss. However, caffeine can also have a significant impact on your health if consumed incorrectly.
Why not understand the effects of caffeine, which is easily accessible in daily life, to create a better lifestyle rhythm and establish sleep habits that positively influence your daily life?
【References】
※1 Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed
※2 The "healing" and "concentration" born from aroma.
※3 [2020] What to eat during menstruation? Explaining foods and drinks that help with menstrual pain (PMS)
※4 Food Safety Commission
