Читать книгу Nutrition For Dummies - Carol Ann Rinzler - Страница 35

If you were to lay your digestive tract out on a table, most of it would look like a simple, rather narrow, tube. The exception is your stomach, a pouchlike structure just below your esophagus, which few non-physicians have ever seen except for those TV viewers addicted to the show My 600-lb. Life.

Like most of the digestive tube, your stomach is circled with strong muscles whose rhythmic peristaltic contractions turn your stomach into a sort of food processor that mechanically breaks pieces of food into ever smaller particles. While this is going on, glands in the stomach wall are secreting stomach juices — a potent blend of enzymes, hydrochloric acid, and mucus.

One stomach enzyme — gastric alcohol dehydrogenase — digests small amounts of alcohol, an unusual nutrient that can be absorbed directly into your bloodstream even before it’s been digested. Other enzymes, plus stomach juices, begin the digestion of proteins and fats, separating them into their basic components, amino acids and fatty acids.

If the words amino acids and fatty acids are completely new to you and if you’re suddenly consumed by the desire to know more about them this instant, stick a pencil in the book to hold your place and flip to Chapters 6 and 7 for the details.

For the most part, digestion of carbohydrates comes to a temporary halt in the stomach. Stomach acids can break some carb bonds, but overall, the liquids here are so acidic that they deactivate amylases, the enzymes that break complex carbohydrates apart into simple sugars. Eventually, your churning stomach blends its contents into a thick soupy mass called chyme (from cheymos, the Greek word for “juice”). When a small amount of chyme spills past the stomach into the small intestine, the digestion of carbohydrates resumes in earnest, and your body begins to extract nutrients from food.