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Will eating a heavy meal make me sleepy? WSJ'sChristina Tsuei takes a look at the science behind a

food coma in the latest installment of "Is It True?"

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You have seconds on turkey and thirds on stuffing. The top button is unfastened to make room for the

pumpkin pie. It is time to step away from the table.

This post-meal recovery period is being studied byscientists who are increasingly finding that what

happens in the body after eating a big meal doesn't

just bring on sleepiness, commonly known as food

coma. It can also increase the risk of later health

problems.

Everybody absorbs fats, sugars and other nutrients

differently. These variations can provide clues about a

person's risk for common medical conditions,

including heart disease, stroke and diabetes, research

shows. Even in healthy people, cells that line the blood

vessels temporarily function less efficiently after a person eats a high-fat meal.

Researchers also are studying strategies for reducing risks in the period immediately after a meal,

known as the postprandial phase. While going for a walk after eating might help digestion, for

example, recent studies suggest that exercising 12 or more hours before the meal can prevent one of

the most damaging effectsa post-meal spike in a type of fat called triglycerides.

One of the biggest tasks for the body after eating is to

deal with fats in the blood. Cholesterol, particularly

LDL, or "bad" cholesterol, infiltrates the walls of the

arteries and forms plaques, which can block blood

flow or eventually rupture, leading to heart attack and

stroke. The condition is known as atherosclerosis.

Triglycerides, which typically peak after a big meal,

are present in food and are also converted by the body

from other nutrients, like carbohydrates.

Triglycerides are particularly problematic because

they are so good at penetrating the arterial wall, says Borge Nordestgaard, chief physician in clinical

biochemistry at Denmark's Copenhagen University Hospital.

Dr. Nordestgaard and his team tracked about 14,000

Danish adults for almost 30 years. Women who had

elevated triglycerides440 milligrams per deciliter,

compared with a normal range of 90mg or

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IN THE LAB NOVEMBER 22, 2011

Countdown to a Food ComaWhat Happens to Your Body After a Big Meal; Clues to Future Health?

By SHIRLEY S. WANG

nksgiving Countdown: Your Health After a Big Meal - WSJ.com http://online.wsj.com/article/SB100014240529702045172045770467...

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shopping list of your picks. Happy holidays!belowhad a 17-fold increase in the risk of heart

attack; men had a five-fold increase. The study was

published in 2007 in the Journal of the American

Medical Association.

In a follow-up study, also published in JAMA, the

research team found that testing for elevated

triglycerides after eating was a better predictor of

future heart attack than measurements taken while a

person was fasting, which is the typical method

during a checkup. Triglyceride counts after eating

also were a more accurate predictor of stroke in

women than were cholesterol measurements,

according to a study published this year in Annals of Neurology.

Spurred in part by the research, Denmark has shifted its clinical practice. Lipid tests are now typically

given to patients who aren't fasting to screen for health risks. If any lipids are elevated, patients then

are also screened in a fasting state, Dr. Nordestgaard says.

Light exercise like a slow walk, done continuously for 30 minutes or more, appears to reduce the peak

in triglycerides that occurs after eating a meal some 12 to 16 hours later, according to research led by

Peter Grandjean, director for the Center for Healthy Living at Baylor University in Waco, Texas.

It's unclear exactly why there is a delay, but exercise induces a number of cellular responses that

require different amounts of time before taking effect, Dr. Grandjean says.

The findings were reported in 2008 in the American Journal of Clinical Nutrition. Other research has

suggested that the benefits of exercise on fat processing can last as long as 48 hours.

The ideal is to be consistently active. But if people are more sedentary and want to time their exercise,it is best to take that long walk half a day before a big meal, Dr. Grandjean says.

"Those people wishing to start an exercise regimen can see beneficial effects on postprandial lipids

with just one session," Dr. Grandjean says.

Some people take niacin to lower triglyceride levels. This seems to work through a different process

than does exercise. People who are taking the medication also should exercise to benefit from both

interventions, Dr. Grandjean says.

Statins, which primarily act to reduce cholesterol, not triglycerides, can have side effects that affect

muscle. People who are on statins should be careful when exercising, medical experts say.

High levels of triglycerides also could be an early warning of diabetes. People who are insulin resistant,

a precursor to diabetes, also typically have elevated triglyceride levels, in the liver and muscle tissues

and in the blood after eating.

Gerald Shulman, a professor of medicine and cellular and molecular physiology at Yale University,

and his team found that insulin resistance appears to start in muscle. If the sugar isn't used by the

muscle, it goes to the liver where it is converted to fat, which is why triglycerides increase in the blood,

according to a report published in 2007 in the Proceedings of the National Academy of Science, or

PNAS.

Even in healthy people, eating a fatty meal can impair the proper functioning of cells that line the

blood vessels, potentially making them more susceptible to atherosclerosis, the condition leading to

heart attack or stroke, according to research by Michio Shimabukuro, a professor in cardio-diabetes

medicine at the University of Tokushima in Tokushima, Japan. The magnitude of the cellular


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Hal Mayforth

dysfunction can accumulate if the fat from one meal hasn't been fully absorbed before the next meal is

consumed, he says. The changes to the blood vessel appear specifically triggered by fat content; a

high-sugar meal doesn't appear to have the same impact, says Dr. Shimabukuro.

Dr. Shimabukuro says reducing the amount of fat in meals can minimize the negative impact on the

blood-vessel cells. Fats from fish and nuts, commonly considered healthier sources of nutrients, don't

appear to cause the same spike in triglycerides as other kinds of fats, and may even help bring down

triglyceride levels, he says.

Scientists also expect that eating smaller amounts of food more frequently is better than eating large

meals, although research in this area is limited.

Dr. Shulman, also an investigator for the Howard Hughes Medical Institute at Yale, has found that

after just six weeks of using a stair-climbing machine, people were essentially able to reverse the effect

of insulin resistance.

Even one 45-minute bout of exercise can improve muscles' ability to use sugar as fuel, according to his

1996 study in the New England Journal of Medicine. In a study published in PNAS this year, Dr.

Shulman also showed that the liver's conversion of sugar to fat slowed after one exercise session.

Nap Time? Mysteries of Food Coma

The urge to nap after a heavy meal like the Thanksgiving feast is commonly referred to as food coma.

But what happens in the body to cause this post-feast dipknown as postprandial somnolence in the

medical communityisn't clear, according to nutrition and sleep experts.

One fact that isn't under debate: Unlike popular

belief, sleepiness isn't caused by a lack of blood

supply to the brain as blood rushes from the head to

the stomach to aid with digestion.

The digestive tract, essentially one long muscle from

end to end, does need additional blood flow when it

begins to move and contract to process food,

according to Lona Sandon, a clinical nutrition

professor at the University of Texas-Southwestern in

Dallas. But the blood tends to come from skin and

skeletal muscle in our limbs, which tend not to be in

use much anyway when we are sitting down and

eating. The brain, on the other hand, is the most

important organ in the body and therefore is

protected and has adequate blood supply unless

under duress, like with a head injury, she says.

The after-meal dragging feeling instead could be associated with changes in certain hormones induced

by the food, says Ms. Sandon, who is also a spokeswoman for the American Dietetic Association. Or it

could be as simple as the feeling of being weighted down by a large amount of food sitting in our

stomachs, she says..

"When you just have this heaviness and this sensation of this bulk in your stomach, you just don't want

to move," she says. "If you have a smaller meal where you feel satisfied but not stuffed, you don't get

sleepiness."

Another possibility is that food coma isn't related to food or digestion at all. Rather, it's because our

bodies are wired to feel tired during the afternoons and evenings when there is a natural dip in the


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circadian rhythm, the internal clock that regulates our sleeping and waking hours, says Robert Basner,

director of Columbia University Medical Center's sleep-studies program.

"I know people seem to think it's due to a meal and it may have something to do with it, but usually

people get sleepy around that time," Dr. Basner says.

A person with a normal sleep-wake cycle will typically feel sluggish around 1 p.m. to 3 p.m. and again

just after midnight, he says. Sitting around after a satisfying meal may make it that much easier to

doze off.

Derek Chong, a professor of clinical neurology at Columbia, agrees that a person's circadian rhythm

can play a major role in meal-time lethargy. But he says food can push us over the edge and into a

full-on siesta session. Food activates our parasympathetic nervous system, which regulates our resting

and relaxation responses, as opposed to the sympathetic nervous system, which regulates our flight or

fight responses, Dr. Chong says.

Tryptophan, of which turkey is a source, may predispose us to sleepiness, but we rarely consume

enough for it to have a soporific effect, says Dr. Basner. Also, people usually ingest so many

carbohydrates during the same meal, which are processed first by the brain for fuel. That makes it

unlikely that tryptophan, which helps make proteins, would actually get to the brain, according to

UT-Southwestern's Ms. Sandon.

"You would have to eat the entire 20-pound turkey to get enough tryptophan to induce sleepiness," she

says.

Christina Tsuei and Shirley S. Wang

Corrections & Amplifications

Michio Shimabukuro is a professor in cardio-diabetes medicine at the University of Tokushima in

Tokushima, Japan (and an adjunct professor at the University of the Ryukyus, in Okinawa, Japan). An

earlier version of this article incorrectly said the University of Tokushima is in Okinawa.


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thanksgiving countdown your health after a big meal - wsj

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