Caffeine and the Night Shift
Circadian health expert and medical scientist Logan Pendergrast, Ph.D., explains how caffeine affects alertness, performance, and sleep — and how night-shift workers can use it strategically instead of habitually. In this video, Dr. Pendergrast breaks down how caffeine works in the brain, its benefits and drawbacks, and the science behind safe daily limits. You’ll learn how caffeine timing, dosage, and metabolism impact both energy and recovery, and why late-shift consumption can cut into your sleep by an hour or more. The lesson closes with practical tools for using caffeine to boost focus at the start of a shift without disrupting rest afterward — helping night-shift workers maintain energy, balance, and long-term health.
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Hello and welcome to the night aling
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education series. My name is Logan
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Pedigrst and I have a PhD in medical
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science from the Kolinska Institute in
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Stockholm, Sweden. And today I will be
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talking to you about caffeine, how it
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works, how it affects our body, and how
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it can be used as a tool to help us
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become more alert during our daily
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lives. So this is our outline for
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today's lesson. We'll start first by
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talking about the broad global usage of
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caffeine. How many people are consuming
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caffeine on a daily basis and what does
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that really mean for the availability of
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caffeine? We'll then narrow it down into
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what caffeine does in our brain and then
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start to talk about some of the benefits
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and drawbacks of caffeine before moving
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into the government recommendations for
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what we should be consuming on a daily
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basis in terms of our caffeine. And then
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lastly, we'll start to talk about some
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tools about how we can effectively use
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caffeine during night shifts or during
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irregular working hours.
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So we'll start by introducing caffeine
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which is as it says here the most common
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psychoactive substance in the entire
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world. So caffeine is consumed on a
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daily basis by 9 out of 10 adults. And
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what this translates to is the
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consumption of about 120,000 tons of
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caffeine globally per year by human
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beings. And this intake of caffeine can
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come from various sources. It can come,
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of course, from caffeine and tea and
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energy drinks, but can also come from
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medications and sodas. And so all of
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these sources of caffeine consumed on a
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daily basis by people can contribute to
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its neurossychological effects, which
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we'll talk about later in this
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presentation. But in the in the US in
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particular, about 85% of adults consume
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caffeine on a daily basis and that
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averages about 180 milligrams per day,
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which is about 1 and 1/2 cups of coffee.
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So, what is caffeine and where is it
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found? Well, caffeine is a naturally
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occurring stimulant and it's found in
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dozens of plants, including, of course,
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coffee beans, tea leaves, and even cocoa
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pods, which is the plant source of cocoa
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beans, which is what we use to make
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chocolate. And it it's also synthesized.
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Caffeine is also synthesized chemically
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and added to various drinks such as of
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course energy drinks but also sodas and
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even medications such as eedrin and
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noodas. And uh an interesting fact here
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is that for energy drinks in particular
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these drinks can contain up to about 500
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mg of caffeine per serving which is
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equivalent to about five cups of coffee.
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So, it's the case that these chemically
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synthesized forms of caffeine can be
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added in large doses to drinks like
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energy drinks and these can even exceed
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the amount that would be in a liquid
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volume that's equal in coffee. So, now
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that we've talked about how many adults
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are consuming caffeine per day and how
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much they're consuming and also the
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sources of caffeine, we can now start to
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talk about how caffeine works. So
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caffeine keeps us awake which we know
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but it does that by blocking the effects
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of adenosine which is a neurom modulator
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that works in the brain to make us feel
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sleepy. It actually binds in the brain
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to the receptor for adenosine and
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prevents adenosine itself from binding
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to that receptor. So in doing so,
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caffeine can kind of delay the feelings
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of sleepiness that we get throughout the
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day and it also indirectly boosts our
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dopamine which is our motivation
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neurotransmitter and also our
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norepinephrine signaling which is a
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fancy way of the of describing the
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adrenaline feelings that we have in our
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brain. So these uh effects of caffeine
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mean that caffeine is not only reducing
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how tired we feel but also increasing
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our motivation in our alertness. And the
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end result is we have an increased very
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alert state that also correlates with an
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increased reaction time better vigilance
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and even like improved performance under
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sleepdeprived conditions. Continuing on
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here with some of the benefits of
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caffeine, we can start first here with
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the improvement in alertness. So,
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caffeine makes us more alert. It helps
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us to pay attention. It also can even
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improve our short-term memory. But these
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effects and these benefits of caffeine
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extend extend beyond the mental realm
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into the physical realm, the the the
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actual physical movement realm. And
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caffeine works in this realm to increase
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our physical performance by increasing
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our endurance, maybe during long-term
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endurance exercise such as cycling or
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running. It also reduces our perception
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of fatigue, which means that as we're
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reaching the end of a workout or an
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intense movement um period, it actually
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makes us feel as though we're working
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less uh intensely. And this is shown in
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studies where they assess exercise
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performance and exercise performance is
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increased by about 11 to 12% when
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caffeine is consumed prior to the
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exercise bout.
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Caffeine however is not risk-free. So
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there are multiple negative effects of
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consuming too much caffeine or consuming
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caffeine at an improper time. Some of
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those effects include jitteriness or
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increased heart rate or even an upset
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stomach in the physical body. But
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critically, caffeine also fragments our
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sleep. Even when it's taken many hours
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prior to going to bed. If we're
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consuming coffee or energy drinks too
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close to bedtime, we can experience a
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fragment of sleep. And this is
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especially problematic for those of us
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who are working shift work where we're
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potentially consuming caffeine in the
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form of coffee or energy drinks near the
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end of our shifts, but then needing to
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go to sleep right when we leave work.
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uh this could fragment our sleep and
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make us less wakeful the following day.
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So, of course, it's important to
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consider caffeine timing when we're
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working uh uncommon hours. And an
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interesting fact here is that when
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caffeine is consumed about 6 hours
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before bedtime, in the scientific
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literature, we see that that equates to
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a reduction in total sleep by about 1
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hour. Which means consuming caffeine too
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close to sleep can reduce the amount of
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sleep that we get by about one hour,
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which is quite significant over the
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course of an entire sleep phase. Now
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that we know what caffeine does in the
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body, we can start to think about how
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long it actually lasts once we consume
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it. So once caffeine is consumed, it can
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take hours to leave the system. This can
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be anywhere from 3 to 7 hours depending
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on multiple factors such as our age, our
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genetics, even some of the enzymes that
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are in our liver and our use of other
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medications. And so what this means is
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that full elimination of consumed
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caffeine can take about 24 hours. And an
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interesting fact here talking about
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consumption of caffeine with other
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factors is smoking. And what we see is
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that smokers actually metabolize
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caffeine more quickly than other
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non-smokers.
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And what metabolize more quickly means
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is that they clear caffeine out of their
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system more quickly. And of course, this
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can be an advantage when it comes to
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wanting to get caffeine out of our
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system before we sleep, but it also can
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reduce the beneficial effects of
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caffeine that we're looking to have when
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we consume our cup of coffee upon
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waking.
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So, how much caffeine should we be
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consuming? Well, according to the US
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FDA, up to 400 milligrams of caffeine
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can be consumed safely in adults per
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day. And what that equates to is about 3
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to four cups of brewed coffee. Now, for
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those uh who are pregnant, that number
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drops to about 200 millig. And then for
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adolescence and children, that number
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drops to nothing. And much of the reason
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for that is that adolescence and
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children lack the proper enzymes to
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clear caffeine from their system.
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Meaning that if those children or
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adolescence consume caffeine, it stays
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in their system for a prolonged period
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of time which could have harmful
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effects.
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So, now that we know all of these
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interesting facts about caffeine,
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whether it's how many adults are
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consuming it, what the benefits and
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risks are, or how long it stays in our
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system, we can now start to implement
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strategies that can help us optimally
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use our caffeine to serve us best,
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particularly for those of us who are
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working shift work. So, starting with
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the timing of caffeine. So caffeine
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ideally for those of us who are working
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shift work should be consumed as early
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as possible upon starting a shift. And
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the reason for that is because if
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caffeine is consumed later in the shift,
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which is closer to our time to go to
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sleep, it can fragment our sleep and
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decrease our wakefulness the next time
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that we wake up. Additionally, consuming
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caffeine in smaller, more frequent
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doses, let's say a cup of coffee every
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other hour, is more effective than
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consuming a large bolus of caffeine,
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let's say an energy drink with 300
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milligrams or a large coffee with 300
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milligrams all in one sitting.
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Additionally, the recommended dosage of
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caffeine for its greatest effect is
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actually something you can calculate.
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And the way that this calculation is
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done is taking 1.4 to 2.7 milligrams of
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caffeine per pound of body weight. And a
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quick shorthand for this would be that
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is about 210 mg to 400 millig for a
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150lb adult. And there's some
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measurements here at the bottom of the
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slide which you can see. And what this
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equates to is a a a serving of um any of
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these given sources of caffeine and how
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much caffeine is in it. So we see here a
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brewed coffee which is about 8 ounces is
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95 millig of caffeine. Caffeine tablets
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such as no dose are about 200 millig of
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caffeine. So twice a cup of coffee.
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Caffeine gum such as this military
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energy gum is about 100 millig. So equal
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to about a cup of coffee. And then these
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energy drinks like Red Bull and Monster
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are anywhere from 80 to 160 milligrams
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per can.
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So to finish up today's lesson, we'll
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just review what we've learned. The
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first is that caffeine is an effective
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neurom modulator, but the timing and the
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dose of caffeine are critical to get the
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benefits. Some of these benefits include
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alertness and stamina, but also
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reductions in fatigue, particularly
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during exercise. And there are also
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drawbacks to caffeine which can uh
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involve sleep disruption, dependence,
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anxiety, feelings of jitteriness, etc.
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So what this means is it is important to
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dose our caffeine properly. And those
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dosages for caffeine that are
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recommended are provided by the FDA,
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which is 400 mg for an adult, which is
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about 3 to four cups of coffee. And then
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lastly, using caffeine strategically,
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not constantly, is the most effective
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and healthy approach to utilizing it,
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particularly for those of us who are
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working shift work. And so that is all
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for today's lesson. Thank you very much
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for listening. This is Logan, and we
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will see you next time with Night
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Owling.