It’s been a whirlwind of work and school recently, with much less time than I’d like devoted to baking, cooking and reading things not related to gastrointestinal processes (not the most appetizing subject). But our unit on digestion is coming to an end and I realize that by some miracle of osmosis I have learned a lot about how to sustain, repair and maintain proper digestion.
In short, our digestive system is sort of like a second skin: it controls the entry of substances from the outside world into our bodies. Digestion begins in the brain when we are excitied by food-related stimuli. In response, the brain sends hormonal signals down to the stomach, liver, pancreas and intestine, alerting them to prepare for an influx of food. Then, as soon as food enters you mouth it begins to be broken down by the enzymes in your saliva. Carbohydrates in particular, are significantly broken down in the mouth, which is part of why they affect your blook sugar and energy level so much more quickly that proteins and fats.
Next the food passes through the esophogus and into the stomach, where hydrochloric acid and pepsinogen are secreted to continue the process of breaking down the food. Pepsinogen is a precursor to pepsin, an enzyme that breaks down protein. Of course our muscle cells, including our stomach, are made largely of protein, so releasing enzymes that break down protein into an organ made of protein doesn’t really seem like the best idea. But, here’s where it get’s cool—pepsinogen is an inactive form of pepsin. It only turns into pepsin when it comes into contact with HCl, and the stomach only releases HCl when it’s mucosal layer is sufficient to protect itself – part of the whole hormonal signal response! If you do not currently have a oozing hole in place of your stomach, give it a pat and a “thank you” for the good work.
After passing through the stomach, the partially digested food passes into the small intestine. Bile (from the liver) and pancreatic enzymes (from—you guessed it—the pancreas) are mixed in, as is bicoarbonate (also from the pancreas) to alkalize all the stomach acid. It is really in the small intestine where the nutrients from your food are absorbed into your body. If your small intestine isn’t functioning properly, it doesn’t matter how healthfully you eat—you won’t fullyabsorb the nutrients.
Absorbtion can occur both transcellularly (across cell membrines) or paracellularly (between cells). Often, intestinal permiability is the cause of a poorly functioning small intestine. This is when, for whatever reason—often food allergies, lack of healthful bacteria, excess stress, excess alcohol consumption or perscription drugs—the intestine allow too many substances/too large of molecules to pass between cells into the blood. Inflammation and antibody response will be triggered as a result, as well as nutrient deficiency. To learn more about supporting a healthy small intestine, check out my nifty handouts: Small Intestine Job Description and Supporting the Small Intestine.
Of course, after passing through the small intestine, “food” (not really food at this point) passes into the large intestine, or colon. It’s here that water is absorbed from the stool and it is compacted to pass from the body. It is also in the colon that much of our friendly gastrointestinal bacteria is located. These friendly little guys help to ferment matter still in the stool and extract and absorb vitamins. Regular ingestion of unpasturized, fermented or cultured foods is great for the bacteria in your small and large intestines—make these tasty foods a part of your daily diet!
Our next unit is school is nutritional biochemistry. A theme to strike fear in the hearts of many a liberal arts major… But on the first day, our instructor for the course, strongly encouraged us all to read Lipton’s The Biology of Belief to gain some perspective on what all the this nitty-gritty chemical stuff really means within the body. I’ve only begun the book, but it is truly fascinating stuff! Maybe biochem ain’t so scary after all…