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Science & Digestion: You Are What You Eat

September 19, 2011

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As children, many of us were told that putting food into our bodies is akin to pumping fuel into a car. In a way, this is true. Just as gas is burned to power an engine, we all know food provides the calories that fuel our movements and involuntary systems.

Unlike a car, however, we are living organisms. Our cells die and need to be replaced. Our fluids must be replenished. Rather than running on only one type of high-octane gasoline, our bodies require a varied diet of different foods to properly support our organs, muscles, bones, and brain. Bits of our food actually become part of our bodies.

Let’s suppose you eat a balanced meal, perhaps a delicious romaine salad with mango, avocado, croutons, and some lean grilled chicken breast. After you consume all those healthy, yummy proteins, carbohydrates, and fats, what happens next?

The carbohydrates from the vegetables, fruit, and croutons will be broken down into their most basic units, or monosaccharides, like glucose, fructose, and galactose. These simple sugars will be absorbed in your small intestine and are converted into quick-release energy.

Fiber, which is a larger carbohydrate, does not break down, but instead travels to the large intestine intact, where it is actually consumed by your gut bacteria for its nutrition and energy. Because it doesn’t break down until much later in the digestive process, it keeps you full for longer. That's pretty neat, isn't it?

While the carbs are mostly broken down and burned for fuel (like in a car), the protein in the chicken will become the enzymes that actually carry out that break down. Protein enzymes are responsible not only for converting carbs to energy, but also for carrying hormones, relaying signals, building new tissue and bone (out of more proteins, of course), and removing old tissue.

The fat in the avocado may get converted into energy (by the proteins), but, as opposed to quick-burning carbs, fats will create slow-burning energy because the molecules are bigger.

Not all of the fat will burn off, though. Some of that avocado will end up forming structures in your body. Every single cell in your body has a membrane made of fat that protects it. Hormones and vitamins are released through fat absorption. Fat insulates your body and protects your organs, too!

The process doesn't sounds much like the mechanics of a car anymore, and that description hardly scraped the surface of the beautiful complexity of human digestion. The important thing to remember is that, in truth, you are what you eat. Literally.

So what foods do you want to be made of?