Please pass the slow twitch fiber…

At the Thanksgiving table, some reach for dark meat, others reach for white meat- my grandfather reaches for the neck! In the sprit of Thanksgiving, and for all the inquisitive minds out there, I thought it might be helpful to explain why turkeys have dark and white meat.

Generally speaking, the meats we eat are muscles and muscles are made out of fibers. The difference between the white and dark meat has to do with the muscle fibers. Muscles perform specific functions. They help us jump, run, stand, walk-and in the case of some animals- fly and swim. They can give us quick bursts of energy or provide endurance for long journeys.

Turkeys do plenty of running around, so the active leg muscles need a lot of oxygen to withstand extended periods of activity. The blood vessels delivering the oxygen contain myoglobin. The greater the oxygen need, the more myoglobin. The more myoglobin the muscles contain, the darker the muscle. Scientists call theses active muscles slow twitch fibers. Typically, the slow twitch fibers are the dark meats.

Turkeys have quick burst of flight– typically from ground to perch — but they are not known for their sustained flying abilities.  The muscles that assist a turkey with quick bursts of flight, such as the breast and wings, do not require a lot of oxygen. Consequently, there are less amounts of myoglobin present in the blood. These “quick burst” muscles are referred to as fast twitch fibers and are fueled by glycogen (carbohydrate stored in body tissues). Fast twitch fibers are typically lighter in color- the white meat of an animal.

You can find more information on this topic from the Why do turkeys have dark and white meat? Webpage.

Here are some more resources from the Library on turkeys and Thanksgiving:

A Much More Respectable Bird A letter from Benjamin Franklin to daughter Sarah Franklin Bache (1784) that reads, “ For in Truth, the Turk’y is in comparison a much more respectable Bird.”

Wiseguide, Who Celebrated the First Thanksgiving? The Library’s Wiseguide magazine discusses the celebrations that predated the 1621 Pilgrims’ Thanksgiving.

Thanksgiving Resources For Teachers Features materials in the Library of Congress that can assist teachers with presentations and activities related to Thanksgiving.