Why is it that so many people complain of sluggishness after lunch? What is it about this particular time of day that makes some of us so vulnerable to fatigue and sleepiness? Why is it so common to have trouble concentrating and paying attention during this period? It really has to do with a balancing act between our intrinsic biorhythms and our environment.
As soon as we awaken, the pressure to fall asleep gradually develops in the form of a sedating neurochemical called adenosine. In fact, caffeine works in part by blocking the actions of adenosine. This buildup during the day is competing against the actions of our normal circadian alerting system that resides deep in the part of our brain called the suprachiasmatic nucleus. There is usually a balance between the two forces and we are alert. As the day progresses, adenosine levels peak and the alerting system tapers, resulting in sleepiness.
However, there are some time warps in this nice balance. Most of us experience a dip in our alerting system between 2 – 4 p.m. Our body temperature drops slightly and this can set in motion feelings of sleepiness and fatigue. If we then add into the mix a prior night of poor quality or quantity of sleep, it becomes almost impossible to avoid feeling sluggish and drowsy.
Diet also plays a large part in the equation. If we eat a lunch high in simple carbohydrates, we set into motion rapid rises in insulin levels. This can result in more of the amino acid tryptophan getting into the brain. Tryptophan is converted to serotonin and then melatonin, resulting in sleepiness.
In addition, having a large meal can divert blood flow from the brain to the intestinal tract. It will also activate the parasympathetic nervous system and suppress the sympathetic (fight or flight) system. This can result in a feeling of low energy and result in a desire to sleep.
So what can we do to counter this afternoon slump?
- We can take a short nap of 15 to 20 minutes. In Spain they call it Siesta.
- We can ensure that we get enough quality sleep at night.
- We can change our midday meal to a smaller one.
- We can add more protein and substitute complex carbohydrates for simple ones.
- We can get some exercise by taking a brisk 10 minute walk after lunch. Exercise can have a definite alerting effect on our minds and bodies.
The bottom line is to become more aware of our intrinsic biorhythms and those factors that can affect them.
By Robert Rosenberg
SEP