Why do I get a slump in mental energy after eating a meal?
—Pranati Kapadia, via e-mail

Paul Li, lecturer of cognitive science at the University of California, Berkeley, offers an explanation: Falling asleep at your desk after that heaping bowl of pasta? You may be experiencing what people commonly refer to as a “food coma.” Medically known as postprandial somnolence, a food coma isn’t an actual coma but rather a lack of mental energy that people often experience after eating a large meal. Symptoms include drowsiness, lethargy and a lack of motivation. But not to worry—this postmeal phenomenon is harmless and can strike anyone who pigs out on foods loaded with carbohydrates, fats or sugars.

What is the link between eating a big meal and feeling sleepy? The process begins as food hits the stomach and small intestine. Eating stimulates activity in the parasympathetic nervous system, which tells your body to slow down and digest. The more food you consume, the more the parasympathetic nervous system revs up, causing your body to focus the bulk of its energy on digestion.

Although large quantities of any food can cause a food coma, common table sugar, or sucrose, found in desserts tends to be the main culprit. As food breaks down into glucose—the simplest form of sugar, which the body uses for fuel—you will experience a surge in blood sugar. To ­counter this spike, your body releases the hormone insulin. Insulin helps to mop up the excess glucose in the blood and returns levels to normal. The increase in insulin also causes your brain to produce more serotonin and melatonin—two neurochemicals that can leave you feeling drowsy. Luckily, this sleepy sensation does not last long—it usually passes after an hour or so.

7 Comments

1. 1. jtdwyer 11:58 AM 12/27/10

   The article states:
   "The more food you consume, the more the parasympathetic nervous system revs up, causing your body to focus the bulk of its energy on digestion."
   
   I'm guessing that the fundamental purpose of these effects are to ensure an increased blood flow to the digestive system by inhibiting other activities. Having suffered congestive heart failure, It seems to me that these effects are more pronounced when the delivery of nutrients to the digestive system is impaired.

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2. 2. Dr.d 11:04 PM 12/27/10

   I prefer my explanation. Any particulate food, whether sugars or a-acids, etc. able to increase the osmotic pressure in the intestinal lumen will draw fluid from capillary circulation to dilute the ingested food and thus causing a transient haemoconcentration that decreases blow flow, especially going up from the heart to the brain and causing a transient blood deprivation of all brain tissue,a feeling of thirst and the symptoms that result from the brain hypoxia. This is the post-prandial symptom. Dr.d

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3. 3. ironjustice 08:39 AM 12/29/10

   The ingredients of the meal make quite a difference.
   "Blood Flow to Heart Hampered After High-Fat Meal"
   

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4. 4. Diesel67 05:06 PM 12/29/10

   <foods loaded with carbohydrates, fats or sugars.>
   
   Sugars ARE carbohydrates. If you mean to exclude complex carbohydrates, just say "fats or sugars." If you mean complex carbohydrates as well as sugars, state "carbohydrates" and don't single out sugars.
   
   Ironjustice - If you're referencing an article, could you please provide the source?
   
   I wish people who write and comment on these boards would check and proofread what they write before they post it.
   
   
   

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5. 5. ironjustice 09:05 AM 12/30/10

   Quote: If you're referencing an article, could you please provide the source?
   Answer: If something is in quotes one can USUALLY simply takes the phrase including the quotes .. "Blood Flow to Heart Hampered After High-Fat Meal" .. and search the phrase by placing it in Google.

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6. 6. ironjustice in reply to ironjustice 09:14 AM 12/30/10

   Quote: "Blood Flow to Heart Hampered After High-Fat Meal"
   
   Answer: This finding below I believe is pretty important.
   "Dr. William Delamater, reported that in older people, if sufficient lecithin was present in the blood, the blood fat level returned to normal in about three hours after a high fat meal. But, if there wasn't sufficient lecithin in the blood, fat and cholesterol levels remained high for as long as twenty hours."
   

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7. 7. Norwin 06:42 PM 1/1/11

   Well, despite the emmerging controversy on terminology and principles, thanks for the article. I am now rescheduling my 14h00 lecture to 15h00, when the 'coma' subsides.

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