Turkey cannot be the only culprit of induced drowsiness after
a Thanksgiving meal.
With the proximity to Thanksgiving, I thought it would be fun to shed some science on the holiday and turkey is a great specimen to study. It is a commonly held assumption that eating copious amounts of turkey, which contain the amino acid Tryptophan, will trigger the drowsiness felt after a large Thanksgiving meal. However, is this assumption true and if so how is Tryptophan the culprit?

Tryptophan is an essential amino acid. An essential amino acid is one that our bodies cannot synthesize, so it must come from food or supplements. Tryptophan is not only a building block in protein biosynthesis in our body but also a biochemical precursor for synthesizing Serotonin, Melatonin and Niacin. Both Serotonin and Melatonin are factors in inducing drowsiness and sleep. Serotonin is a neurotransmitter that facilitates emotions including desire, body temperature, sleep, appetite and metabolism. Serotonin can also be converted into Melatonin, which further regulates sleep, maintaining the circadian rhythms of several biological functions.

The foods that contain Tryptophan are usually protein-based and include chocolate, oats, milk, yogurt, cottage cheese, red meat, poultry, fish, eggs, along with specific nuts and certain fruits. However, turkey contains the same amount of Tryptophan of other meats. Most meats contain .25 grams of Tryptophan per 100 grams of food while dried egg whites contain 1 gram of Tryptophan per 100 grams of food. Turkey cannot be the only culprit of induced drowsiness after a Thanksgiving meal. If this was indeed true, people would be drowsy after any normal meal containing meat as the levels of Tryptophan are equivalent.

The other two denominators with the Thanksgiving meal are high carbohydrates and fat. An average Thanksgiving meal can have 3000 calories and 239 grams of fat. In comparison, United Nations FAO says the average American consumed 3770 calories per day in 2001-2003. It has been shown in studies in both animals and humans that a meal high in carbohydrates and fat triggers Insulin. Insulin them stimulates the uptake of large neutral branched-chain amino acids, known as LNAA.

Tryptophan does not fall into the LNAA family and thus the ratio of Tryptophan to LNAA in the blood stream increases when Insulin is released into the blood stream. Less competition for transporters in the blood stream results in the uptake of Tryptophan across the blood-brain barrier and the synthesis of Serotonin and Melatonin. This in turn creates the lethargy and drowsiness common after the Thanksgiving meal. Therefore it is not turkey alone that ends in a nap after Thanksgiving dinner. It is a collaborative process. Without the intake of carbohydrates dressed up as rolls, sweet potatoes, mashed potatoes, stuffing and pumpkin pie, the Tryptophan in the iconic Thanksgiving turkey would have too much competition for synthesis. Insulin clears away the competition and in turn isolates Tryptophan in the blood stream enabling it to be readily synthesized. The whole meal is responsible for the drowsiness. The next question that could be posed is this the body’s way to have us slow down to aid digestion?

Yep, I love eggs: scrambled, poached, deviled, fried, boiled, and my favorite, egg in a basket. They are the perfect breakfast or power-ball snack. I also love the idea of purchasing eggs from farms that raise them with kindness and humanity, and that has proven a bit challenging. There are many terms to decipher, but armed with correct information, we can all help chickens and still enjoy those eggs. The following chart gives information about a few local farms and is thanks to my favorite place to grocery shop, Rainbow Grocery.

Organic Fed / Certified Organic

All organic eggs are certified by the USDA. Organic eggs come from hens whose feed is free of pesticides, herbicides, fungicides, and commercial fertilizers. Organic chicken feed contains no animal byproducts and the hens have never been given antibiotics.

Hormones and Antibiotics:

The FDA banned the use of hormones – most notably diethylstilbestrol, or DES – in poultry in 1959, after they not only caused tragic health problems in consumers but also failed to stimulate growth in chickens. "Hormone free" is a misleading bit of marketing that suggests other egg producers are illegally dosing their birds.

Kept in Cages

Some hens are kept in battery cages; enclosures so small the animals can't spread their wings. Battery caged hens are crammed as many as six chickens into a cage at a time, leaving each bird with less personal space than a sheet of ordinary notebook paper. Critics say the battery system causes the spread of disease, requires the painful de-beaking of birds, and restricts natural bird behaviors, such as dusting or nesting.

Have Access to Outside

"Free Range" and "Free Roaming" are terms that bring to mind idyllic barnyard scenes. These labels, which are regulated by the USDA, may be used by a producer if their hens are allowed some access to the outdoors. This does not guarantee constant access, nor is there any specification of the size of the outdoor area (which is, of course, a penned area, not a range).

Beaks Clipped

Also known as debeaking, or beak trimming, is a process by which parts of the beak of a chicken or turkey are trimmed. Many variations of debeaking are used. Most commonly, the beak is shortened permanently, with the lower beak somewhat longer than the upper beak. The goal of this is to reduce cannibalism in stressed-out bird populations, such as in crowded egg-laying hen houses.

Forced Molted

When light and temperature are manipulated so hens lay eggs more than normal.

Omega-3 enriched

Omega-3 is a polyunsaturated fatty acid considered crucial by some for developing brains and preventing heart disease and depression. Farmers boost the omega-3 content of their hens' eggs by adding ground flaxseed, algae, or even fish oil to the birds' feed.

My own kind choice is to stay informed, shop at the local farmers' market and ask questions, and someday, raise my own.

If you have any tips or insights into local egg farms, please do share!

For more egg carton terms, go to:

http://blog.pennlive.com/naturalliving/2007/06/eggs.html

Amy Gotliffe is Conservation Manager at The Oakland Zoo.

A wishbone from a theropod and a turkey.This week, many of us celebrated one of the most American of holidays: Thanksgiving. Following tradition, most of us probably had a bite or two of turkey — if you were one of the fortunate to get your hands dirty, you may have used this New York Times video as a guide.

What you may not know is that we can find homologies of many birds parts — thigh bones, arm hones, and even wishbones — in our own skeleton, and it's not happenstance. The ultimate reason for this similarity is ancestry: birds, mammals and all other tetrapods (four-legged, air-breathing vertebrates) share a common ancestor, over 300 million years old. And, as the descendents, we all exhibit the same basic body plan, with additional anatomical refinements specific to each evolutionary history. Whether a tetrapod's arm is a fin, a wing or a limb throwing a baseball, a common structure is shared among them because of their evolutionary past.

Back to turkeys: in your holiday meal, you may have come across a very particular y-shaped bone: the wishbone. (The one from my turkey is drying on the counter above the kitchen sink). Humans actually have homologues of wishbones, but we don't call them that — they're our collarbones, or clavicles. These bones are long and slender, and they form a key part of complex of bones and muscles that allow us to move our arms. Living birds are unique among tetrapods in having clavicles that are fused together into the y-shaped structure called a furcula, and it plays a key roles in allowing birds to fly. Furculae stiffen the thoracic skeleton, and, in conjunction with a keeled breastbone (or sternum), they provide key muscle anchors for the unique flight stroke of the bird arm.

So, how did two bones get fused into one? Birds are descended from one particular line of dinosaurs called theropods, which includes dinosaurs like T. rex or Velociraptor. Over the last 20 years, paleontologists have assembled a detailed picture of the family tree, or phylogeny, of these animals, showing the exact anatomical changes that occurred along the lineage of theropods to living birds. The changes in the furcula plays a key role in this evolutionary sequence: it turns out that relatives of T. rex and many other theropods had fused furculae, but clearly these animals did not use the fused furcula to fly. Some paleontologists have suggested that fused furculae in theropods increased the mobility of the forelimbs. Then, as birds evolved flight, a fused furcula turned out to be wonderfully useful as a brace for a flapping limb.

Evolution often works in this manner: recruiting old structures to use in a new context, and many examples of such improvisation have been shown in the fossil record. Together, phylogeny and the fossil record reveal more about evolution that might not have been apparent when you were first biting into that savory chunk of turkey meat. To check find out more about your holiday dinosaur, check out this link too.

Nick Pyenson is a PhD candidate at the University of California, Berkeley, in the department of integrative biology and the museum of paleontology.

latitude: 37.7819, longitude: -122.286