Do you know what perks things up? COFFEE! But how much should you have? After a bad night of sleep, how many cups of coffee do you need to function as normal? Is it safe to go back for more coffee during that late afternoon meeting, or will it keep you up all night? How much caffeine is even in coffee, anyway?

How Caffeine Wakes Us Up

Whether consumed in coffee or other substances, caffeine is a stimulant that gives us that desired jolt of energy to temporarily replace that slow, groggy feeling. It makes us feel more alert by increasing adrenaline production and blocking sleep-inducing chemicals in our brains! It also prevents adenosine from binding to our receptors to signal that it’s time for sleep.

A typical dose of caffeine is between 50 mg to 200 mg, and one cup of coffee has about 95 mg. Levels of caffeine peak in the blood about 15 to 45 minutes after consumption, but it will linger in your system with a half-life of about five hours. For example, if you consume 40 mg of caffeine, in five hours, you will still have about 20 mg in your system.

Recent studies suggest that gaining three hours of extra sleep is equivalent to 200 mg of caffeine. Caffeine can sustain performance during tasks that require higher cognitive functions despite sleep deprivation. For those in careers without regular schedules, such as truck drivers and military personnel, it may help with tasks like driving, using working memory, and decision-making.

NOTE: Caffeine or drinking coffee will not help a person sober up.

However, with continued sleep loss, caffeine will begin to lose its effects in terms of the ability to maintain alertness and wakefulness. Building a caffeine tolerance during periods of prolonged sleep loss may make it more difficult to recover.

As far as helping us remain focused and combating fatigue, caffeine is not a long term solution for sleep loss. The benefits of coffee or other forms of caffeine decrease as your sleep debt increases. After day four or five of losing sleep caffeine loses its effectiveness.

What Caffeine Does To Our Body

Along with making us feel alert when caffeine blocks adenosine, dopamine levels increase. Dopamine is a neurotransmitter that makes us feel good, so increased levels create a sense of happiness and well-being.

As caffeine passes through our throat, stomach, liver, and kidneys, it affects more than just our brains too! Theophylline, found in caffeine, relaxes smooth muscles in our bodies. Theophylline can help people with asthma breathe, and it also relaxes the smooth muscles in the colon, which is why coffee sends people to the bathroom.

Theobromine helps your brain and muscles use an increased level of oxygen and nutrients for more energy. Also, metabolite theophylline, which is found in caffeine, relaxes artery walls and opens blood vessels for greater blood flow.

How Caffeine Is Metabolized

Age, medical conditions, drug interactions, and caffeine sensitivity all impact the rate at which your body metabolizes caffeine. For example, nicotine speeds up the rate at which it’s metabolized, and oral contraceptives taken by women can double its half-life.

As caffeine reaches the liver, it’s metabolized with the CYP1A2 enzyme. The ability to produce this enzyme is regulated by the CYP1A2 gene, meaning your DNA sequence of this gene determines how well you can metabolize and eliminate caffeine from your body.

Depending on your genetic makeup, you may produce a little of this enzyme or a lot. Most people fall somewhere in the middle. But 10% of the population metabolizes caffeine at a rapid rate with low sensitivity.

There Are Three Levels Of Caffeine Sensitivity

1. Caffeine Hypersensitivity

If you’re hypersensitive to caffeine, then your body reacts to a minimal amount. Having a serving as small as 100 mg can cause overdose symptoms such as the jitters, insomnia, and a rapid heartbeat.

2. Caffeine Normal Sensitivity

If your body reacts normally to caffeine, then you can enjoy a moderate dose of caffeine (200 mg – 400 mg daily) without any adverse reactions. However, remember to stop drinking caffeine early enough in the day to prevent disrupting your sleep.

3. Caffeine Hyposensitivity

People may find themselves reaching for more and more cups of coffee in an attempt to battle fatigue, but more isn’t always better. Using caffeine to offset chronic sleep deprivation may cause caffeine to lose its effectiveness and negatively impact rest by decreasing the amount of time spent in the third stage of sleep.

The Effects Of Too Much Caffeine

People may find themselves reaching for more and more cups of coffee in an attempt to battle fatigue, but more isn’t always better. Using caffeine to offset chronic sleep deprivation may cause caffeine to lose its effectiveness and negatively impact rest by decreasing the amount of time spent in the third stage of sleep.

One study on the effects of caffeine on sleep found that when a fixed dose of caffeine was administered to patients at bedtime, three hours before bed, or six hours before bed it caused significant sleep disturbances.

As it is a stimulant, even if you don’t feel the effects of coffee (or caffeine from other sources) in your body, it doesn’t mean it’s not impacting your ability to fall or stay asleep.

While a moderate dose of caffeine – which is equivalent to three 8oz cups of coffee (285 mg of caffeine) – isn’t associated with any health risks, any more than that is an excessive intake.

Symptoms of too much caffeine include:

  • Anxiety

  • Irritability
  • Rapid heart rate
  • Frequent/excessive urination
  • Nausea
  • Heartburn
  • Headache
  • Insomnia or sleep disruption
  • A caffeine crash

What Is A Caffeine Crash?

A caffeine crash can occur when high levels of caffeine begin to exit the body. As caffeine helps us stay alert, levels of adenosine continue to build in the brain, then once caffeine is metabolized, its effects begin to wear off.

This leads to all of the built-up adenosine flooding your brain receptors, signaling that it’s time for sleep at a much more intense level. With a caffeine crash, people often feel more tired than they did before.

Caffeine crash symptoms include:

  • Heavy fatigue
  • Poor concentration
  • Irritability
  • Depression
  • Dozing off
Sleep_Disorder_Insomnia_Tired

To avoid a caffeine crash:

  • Get enough rest to start the day with normal adenosine levels.
  • Spread out coffee or caffeine consumption throughout the day. Instead of downing cups of coffee back to back, spread each cup out by a few hours.
  • Keep consumption at a moderate dose (200 mg per single dose).
  • Eat healthy meals and avoid drinking caffeine on an empty stomach. Nutrition from food provides proper energy, while coffee only provides temporary energy.

How To Tell When Caffeine Is Wearing Off

As caffeine exits your body through urine after being filtered through your kidneys, you may feel fatigued, have some muscle weakness, and feel a little depressed. Depending on how many hours you have before bedtime and the amount of caffeine you’ve had during the day, it might be time for another cup of coffee.

Caffeine can be addictive, so if you quit cold turkey, you may notice some unpleasant side effects of caffeine withdrawal, such as muscular tension, severe headaches, nervousness, constipation, and irritability.

Symptoms may appear as soon as 12 to 24 hours after quitting caffeine and may last about a week. It’s recommended to slowly reduce the amount of caffeine you consume instead of quitting all at once.

The Takeaway

Caffeine can be used as an effective stimulant to help you remain energetic and focused when consumed in moderate amounts. It’s not a long term solution for lack of adequate rest, and large quantities may cause insomnia. Be sure to use the coffee calculator to determine how many cups you can have to offset sleep deprivation without disrupting your rest tonight.

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