Most times we feel drowsy after eating some foods. This might occur as a result digestion patterns and sleep cycles. Some researchers has come up with theories as to why this happens; but they still agree it’s a natural response and not a cause for alarm.
Drowsiness after eating is due to an increase in energy levels which could be termed ‘postprandrial somnolence’.
Postprandial somnolence (colloquially known as the itis food coma, after dinner dip, or postprandial sleep) is a normal state of drowsiness following a meal (regardless of the time of the meal). Postprandial somnolence has two components: a general state of low energy related to activation of the parasympathetic nervous system in response to mass in the gastrointestinal tract, and a specific state of sleepiness. While there are numerous theories surrounding this behavior, such as decreased blood flow to the brain, neurohormonal modulation of sleep through digestive coupled signaling, or vagal stimulation, very few have been explicitly tested.
Insulin, large neutral amino acids, and tryptophan
When foods with a high glycemic index are consumed, the carbohydrates in the food are more easily digested than low glycemic index foods. Hence, more glucose is available for absorption; and the more the glucose, the more the amount off insulin for absorption. Insulin stimulates the uptake of valine, leucine, and isoleucine into skeletal muscles, but not uptake of tryptophan. This however, lowers the ratio of these branched chain amino acids in the bloodstream relative to tryptophan (an aromatic amino acid), making tryptophan preferentially available to the large neutral amino acid transporter at the blood–brain barrier. Uptake of tryptophan by the brain thus increases. In the brain, tryptophan is converted to serotonin (the hormone responsible for moods and sleep cycles) which is then converted to melatonin. Increased brain serotonin and melatonin levels result in sleepiness.
Insulin also can cause postprandial somnolence via another mechanism. Insulin increases the activity of Na/K ATPase, causing increased movement of potassium into cells from the extracellular fluid. The large movement of potassium from the extracellular fluid can lead to a mild hypokalemic state. The effects of hypokalemia can include fatigue, muscle weakness, or paralysis.
Some health experts also suggests that food coma could be caused by a slight shift in blood flow away from the brain to the digestive organs. Eating helps activate the parasympathetic nervous system.
The PNS regulates certain processes in your body like slowing the heart rate and regulating blood pressure and digestion. The PNS is triggered when the stomach expands from accommodating a large meal. As a result of this, blood flow is directed to the working digestive organs and less to the brain. This slight diversion may cause you to feel drowsy and fatigued.
Why do people feel tired after eating?
Apart from the physiology explained above, a person may feel tired after eating due to what, when and how much the person consumes per sitting.
A large meal would obviously lead to a rush of insulin to help in absorption and moving of glucose to cells where they are needed.
A person’s circadian rhythm might affect how they feel after eating; well, that doesn’t mean calories know time.
The National Sleep Foundation reports that people naturally have a lull in energy 2.am and again at 2pm which might explain why you have to take a nap after lunch. Meal timing are very essential.
• Small but frequent meals are preferable to very heavy meals.
• Quality sleep matters.
• Light exercise after eating would help. A walk would do.
• Avoid drinking alcohol with meals.
• Do more of fluids.