Question: Why Am I Sleepy After Eating Lunch?
As you return to your work after eating lunch, you may wonder: why am I so sleepy? Whether you use words like drowsiness, sleepiness, tiredness, or fatigue
to describe this mid-afternoon lull, why does it occur? Learn about how
feeling sleepy after eating lunch may actually relate to a natural dip
in the circadian rhythm. In addition, consider a few ways to counteract
this desire to fall asleep.
Answer:
It is normal to feel a little
sleepy after eating lunch. Some people may mistakenly think that it
relates to the consumption of food. In particular, some believe that
there is a significant shift in blood flow from the brain to the stomach
or gastrointestinal tract to aid in digestion. Although this sounds
plausible, it doesn’t really make that much sense. If this were the
case, why wouldn’t we feel just as sleepy after eating a large breakfast
or after dinner? The truth is that this sleepiness is unrelated to
meals and is due to another cause.
Others may argue that there are
elements within food that cause sleepiness. For example, there are
minuscule levels of the hormone called melatonin.
Although melatonin has an important role in the timing of sleep, the
low levels within food are unlikely to have any significant effect.
There are some other foods that might make you feel a little sleepy,
most notably turkey and foods that contain tryptophan.
In addition, drinking alcohol may cause
drowsiness. In most cases, this is not what contributes to feeling
sleepy after lunch, however.
In fact, it has little to do with the
food eaten (or that eating has occurred at all). Instead, it has more
to do with the natural timing of an increased propensity towards sleep.
There are two phenomena that contribute to this: the homeostatic sleep drive and the circadian rhythm. The sleep drive is due to the gradual build-up of a chemical within the brain called adenosine.
The longer that a person stays awake, the more adenosine accumulates,
leading to an increased desire for sleep. This reaches its peak right
before bedtime, but it is also higher in the afternoon compared to the
morning.
The second process that contributes indirectly to sleepiness is the circadian rhythm.
The circadian rhythm is actually the pattern of an alerting signal. It
increases throughout the day to keep us awake and counteract the
increasing levels of adenosine. There is a shoulder or dip in this
pattern in the early afternoon, typically 7-9 hours after waking up.
When the alerting signal dips, the underlying sleepiness shows itself,
and we feel sleepy.
Although feeling drowsy after lunch can be explained, there may be times when we are too sleepy. If we experience sleep deprivation, this after lunch sleepiness can be more pronounced.
In addition, sleep disorders such as obstructive sleep apnea may make this worse.
To counteract the sleepiness that occurs in the early afternoon, you can try using caffeine
or even take a short 10-20 minute nap. Fortunately, if you tough it
out, this period will pass and you will find that you feel more alert
again in a matter of hours.
Source:
Kryger, MH et al. "Principles and Practice of Sleep Medicine." Elsevier, 5th edition.
