The body's reaction to Turkey Day


Staff Writer

The scene is sometime after Thanksgiving dinner in almost any house in the country. Lethargic people lie in motionless heaps on the furniture, half-napping over their bulging stomachs. And on the table are the remains of the possible culprit: the turkey.

The traditional main dish contains a secret weapon in the form of the chemical tryptophan, which causes drowsiness under the correct conditions. But the case is confusing -- for such a stupor results from any big meal. And holiday feasts tend to be full of fat, carbohydrates and alcohol, all of which contribute to a sense of fatigue.

So what's to blame for the Turkey Day sluggishness?

"I feel that it's the Thanksgiving dinner as a whole -- the whole setting," said Janice Baker, a registered dietitian at the Centre for Health Care Medical Associates in Rancho Bernardo. "It's relaxing. People are eating more. It's not really so much to do with the turkey. After you've eaten a pretty big meal, you don't feel like going out for a jog. It's a relaxing time just to hang out and talk."

Baker said tryptophan has a warranted reputation for promoting sleep. However, the amino acid's major job is to make protein in the body. Tryptophan, like the other eight basic amino acids in its gang, is found in animal products and many other foods containing protein.

"It is definitely an essential building block for the body -- it makes all of our body proteins," said Mark Kern, who is an associate professor of exercise and nutritional sciences at San Diego State University. "And it has other functions, too. It can make niacin in our body, which is one of the vitamins that we need."

Kern said enzymes in the body aid and abet tryptophan in its transformation into one kind of neurotransmitter, which is any substance that transmits nerve signals in the brain.

"It gets converted into a neurotransmitter that people have heard a lot about lately, which is called serotonin," Kern said.

He said serotonin lures people into feeling mellow as well as drowsy. Some types of antidepressants elevate levels of serotonin. People also once used tryptophan for sleep until contaminated pills caused problems. The pills actually work best in the absence of protein because rival amino acids can compete for attention in the body.

"When you eat carbohydrates, you stimulate insulin," said Gaila Mackenzie, a doctor who specializes in nutrition in Escondido. "Insulin is what carries sugar into the cell wall. Increasing insulin increases the uptake of tryptophan by the brain."

The insulin also clears many of the amino acids out of the bloodstream, allowing the tryptophan to outcompete the other amino acids in reaching the brain. But the tryptophan in turkey is actually the least likely suspect for what makes people start nodding off after Thanksgiving dinner.

"Most of the sedation that you get from a big meal is simply from the big meal," said John D. Hill, a doctor who specializes in nutrition and has a family practice in Solana Beach. "You tend to get tired. All the blood is circulating to the stomach, so there's less oxygen going around."

The gastrointestinal tract needs the oxygen to break down proteins into amino acids, fats into lipids and carbohydrates into sugars. The entire body devotes itself to dealing with the overload of food after a holiday meal to turn the tempting treats into its own energy, fat and protein.

"It's doing a lot of things," Hill said. "And the bigger the meal, the more it has to do and the faster it has to do it."

The criminally rich dishes of the typical holiday get-together slow down the absorption of a meal.

"Fats slow down the digestive process," said Mackenzie, who also specializes in natural medicine. "It takes a lot to digest a fat."

Mackenzie said the seductive carbohydrates in bread, dressing, potatoes and pumpkin pie add a whole new twist. They help the body turn tryptophan into serotonin, and they have a dark side.

"The problem with the carbohydrates is your blood sugar goes up," said Morris Wisniewski, a doctor who specializes in nutrition and internal medicine in Vista. "And then within half an hour to an hour and a half, your blood sugar comes crashing down quickly. And that's a big cause of fatigue."

He said the gravy, with its fat and carbohydrates, might force more people to yawn than the turkey. Wine, beer or other drinks also cause people to doze off because alcohol assaults the nerve signals in the brain. In the end, staying in after a holiday meal to recover might be a good idea for the people who dare to overindulge.

"My big thing is, more than anything else, not to stress so much about the food, but to maintain regular physical activity -- just to keep people in balance," said Baker, who is also a certified diabetes educator.

But the jog can probably wait until the morning after family and friends enjoy flirting with dangerous foods. And the leftovers probably won't make anyone too groggy at lunchtime.

"If you ever had turkey slices, did you notice significant fatigue afterward?" Wisniewski asked. "Probably not."
