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December 17, 2015

Digesting – and dispelling – a few holiday eating myths

If you spent Thanksgiving like many people, you celebrated the holiday, in part, by sitting down to a dinner of turkey, stuffing, cranberry sauce, plus assorted side dishes and desserts.

If you're anything like me, you mindlessly scarfed down as much food as possible, interrupted only by large gulps of red wine every now and then, and followed by a hearty nap session. Needless to say, Thanksgiving starts the holiday season, but Christmas and New Year's beckons with more opportunity for overeating and overdrinking.

With the taste of turkey still on the lips, and the thought of more gluttonous occasions ahead, maybe even more Christmas bird, or ham or beef, I decided to look into the science behind some common eating myths.

For instance, is it possible to eat so much your stomach explodes? It certainly feels possible at this time of year, but what does the medical literature say? Is dark meat really worse for your health than white meat? And does turkey really make you sleepy, or is any gigantic meal nap-inducing?

Can your stomach explode from eating too much food?

Although figures up to 3,000 calories have been cited, even an excessively large meal would likely weigh in at a little under 2,500 calories, according to calculations made by The New York Times. That number includes portions of white and dark turkey meat with skin, a whopping seven side dishes, and two slices of pie with generous dollops of whipped cream. A large meal like that can take up to half a day to digest and lead to indigestion, gas and fatigue.

But what it won't do is make your stomach explode. The human stomach can normally hold about 1 to 1.5 liters of food and drink, which is the point where most people feel full. Huge holiday feasts probably stretch the stomach beyond the point of comfort, perhaps up to 2 or even 3 liters of stuff – but this is still an amount that pathologists estimate as being in the safe zone.

In the gruesome cases describing patients who have died from a ruptured stomach – a rare but entirely possible occurrence – they have often binge-eaten five or more liters of food, as reported by NBC News. At that point, the stomach muscles become too stretched out to induce vomiting, and the organ's walls tear open, releasing its contents into the abdominal cavity. The bacteria that safely populate the gut can then cause infection, and the patient may die without antibiotics, proper cavity clean-up, and suturing of the stomach.

Why does turkey contain two types of meat – white and dark – and which one is healthier?

Many of us will put roast turkey back on the table for dinner on Christmas Eve or Day. So what's healthier? The white meat or the dark? We all have our preference, but what makes one cut of turkey darker than another? The breast contains white meat, which finishes cooking at an internal temperature of 160 degrees F, while the meat in the thighs and legs has a darker hue that is done at 165 degrees F.

The difference in meat color, caused by the type of muscle and how active that body part is, makes turkey a challenging dish to cook perfectly since the white meat tends to dry out. According to the Library of Congress, turkey thighs and legs contain blood vessels full of myoglobin, or muscle hemoglobin, that delivers oxygen to the muscles. Since turkeys run around a lot, these parts have more myoglobin, which leads to darker muscle.

Breast meat is white because turkeys are flightless and, as a result, don't use these muscles much. There's no need to transport large amounts of oxygen to the breast muscles, and so they contain much less myoglobin than the thighs and muscles.

White meat has long been labeled healthier than dark meat for turkeys and other types of poultry, and indeed it has less calories, saturated fat and cholesterol than its myoglobin-heavy counterpart. According to the U.S. Department of Agriculture, roasted turkey breast contains 160 calories, 2 grams of saturated fat, and 60 mg cholesterol per 3 oz. serving, while roasted turkey thighs stack up at 190 calories, 3 grams of saturated fat, and 75 mg cholesterol for the same amount of meat.

(For the sake of comparison, a 3 oz. serving of baked ham contains 130 calories, 1.5 grams of saturated fat, and 60 mg cholesterol, and the same amount of roast beef contains 170 calories, 3 grams of saturated fat and 70mg cholesterol.)

Turkey is high in tryptophan, an essential amino acid that helps produce the neurotransmitter serotonin in our bodies. But does it make us drowsy? (budgetstockphoto / iStock)

Does eating turkey really make you sleepy?

Did you nod off on the couch at Thanksgiving? We've all heard the science behind why eating turkey makes you crave a nap – turkey contains lots of something called tryptophan, which promotes drowsiness – but is it true?

This explanation initially appears logical. Tryptophan is an essential amino acid, which are the building blocks of proteins, and is used by our bodies to produce the neurotransmitter serotonin. A hormone strongly associated with sleep, melatonin, is made from serotonin. The pineal gland, a pea-sized organ in the brain, normally releases melatonin a few hours before your regular bedtime and prepares your body for sleep.

Turkey meat is heavy on the tryptophan, so that could explain the inevitable drowsiness that follows, right? The problem with this argument is that, while turkey does contain a good amount of tryptophan, so do other types of poultry – in fact, chicken actually has slightly more than turkey – milk, fish, and even cheddar cheese. Of all the amino acids contained in a typical Thanksgiving or Christmas dinner, tryptophan is probably the least likely to make it to your brain and works much better as a sleep-inducing agent when taken on an empty stomach.

So instead of blaming the bird for your post-meal grogginess, experts say the real culprit is our overindulgence on food and drink in general, and specifically during the holidays. When we eat a big meal, our bodies work to hard to digest everything, meaning blood flows to our stomach and intestines instead of elsewhere. Studies have also found that high blood glucose levels can switch off the neurons that keep us awake and alert, as reported by The New Scientist.