The circadian rhythm, blood circulation and even the choices we make at the dinner table influence daytime sleepiness. Small changes can make a difference
You have probably already had the impression of receiving sleep or “soft” after lunch, or heard someone say. The critical period for drowsiness seems to be between 2 p.m. and 5 p.m., when eyelids begin to droop, concentration wanes, and the urge to shut up sets in.
The reasons can be many, ranging from a poor night’s sleep to illnesses that should not be ignored, such as obstructive sleep apnea, anemia or thyroid disorders.
However, the culprit is probably yours. circadian rhythm. Although people associate the internal clock just sleep and the times when they are awake or alert, the circadian rhythm is also linked to blood pressure, appetite, body temperature or hormone levels.
“A kind of momentary hibernation”
CNN Portugal medical correspondent Pedro Gomes Sena explains that there are “several mechanisms related to this phenomenon” of drowsiness after lunch.
“First, after lunch, a lot of blood flow is directed to the digestive tract, which causes the central nervous system to go into lower performance levels, which makes us feel somewhat drowsy. When we eat, it there is also a set of hormonal changes, depending on the foods we eat, that promote this phenomenon.There is also an evolutionary point of view, because if we go back in time when human beings ate, it was at certain times that the alert levels could drop, so we entered a kind of temporary hibernation, ”says Pedro Gomes Sena.
Studies indicate that human vigilance tends, as a general rule, to be lower at two times of the day: at dawn, between 2 a.m. and 7 a.m., when a large part of the population is asleep, and after noon, between 2:00 p.m. and 5:00 p.m., when most are working.
After lunch, the blood circulation changes to accommodate more blood flow to the digestive system, which means the amount of blood reaching the brain decreases, which can trigger some level of fatigue. The CNN medical correspondent also recalls that “the pancreas has a spike in insulin after eating, which also causes increased drowsiness”.
We also have hormones, neurotransmitters and molecules involved in this whole process. One is orexin, a neuropeptide that affects hunger and helps the body stay awake. What happens after eating food is that glucose levels rise and this can inhibit this neurotransmitter.
Other surveys reveal that fatigue may be associated with fried foods, saturated fats, and high-calorie meals. The Mediterranean diet, recommended in Portugal by the health authorities, seems less linked to this state of drowsiness.
Strategies to combat drowsiness after meals
A good option to minimize post-meal drowsiness would be, for example, to eat more vegetables than carbs for lunch, as they are high in fiber and can be helpful in regulating blood sugar.
Temporary tiredness can also be stopped by a brisk walk, preferably outside, thanks to natural light. O coffee can also be an ally, adds Pedro Gomes Sena.
“A walk or exposure to intense natural or artificial light can be relatively quick fixes to this phenomenon, as these are activities that end up being exciting. This happens because, if we stay active, the muscles contract and the brain is forced to keep up with those activity levels as well. With light, the principle is exactly the same as that which advises against using a mobile phone or a tablet at bedtime. However, if the meal was very heavy and you ingested alcohol, too strenuous a walk can be counterproductive, because you will feel bad, “explains the doctor.
If all else fails, you can always try a quick 25-30 minute nap, which should help improve cognitive performance. Pedro Gomes Sena recalls that it is “a way of responding to the circadian rhythm”, concluding that “thanks to a brief rest it is possible to channel energy towards the digestive process, the brain manages to have a window of time to recover and we end up being more deserted when we wake up”.