Digestion 101: Part 3

Have you read parts 1 & 2 of this article yet, if not, go back and do that now! 

Ladies and gentlemen, we have finally arrived at Ground Zero of digestion—-the stomach. Woo-hoo!

I like to think of it as Ground Zero because when most people think about digestion (which I’m sure is almost never because most people aren’t weird Food Nerds like me), the first thing they probably thing about is the stomach. But looking at the whole north-south progression, it’s actually right in the middle, between the brain and the mouth above and the small intestine and large intestine below.

Either way, here we are!

After the food has left the mouth (and it’s now called a bolus, by the way), it makes its way down the esophagus to the stomach’s first gatekeeper: the upper esophageal sphincter, sometimes called the cardiac sphincter. When the gate opens the food drops in, and now the magic begins (or things start to go wrong, depending on your particular situation).

Remember when we were talking about the mouth, and I told you how there food is broken down both mechanically (chewing) and chemically (salivary amylase and other enzymes)? It’s the same deal with the stomach. When the food drops in,cells called G cells spring into action. They start producing stomach acid (HCl) and pepsin. That’s the chemical part. Now, if for whatever reason you weren’t parasympathetic when you started to eat your stomach will not produce as much HCl which will impair the chemical aspect of digestion. In addition, as we age we start to lose G cells and is another way we lose digestive function. Less G cells means less stomach acid.

Keep in mind, there is a physical aspect to digestion as well. The stomach is lined with muscles which contract in three different directions to help churn the bolus into the final product, chyme. But is that enough to fully break down food?


Especially not when it comes to protein. To digest food properly and break those proteins down into amino acids that the body can properly absorb, the stomach needs to be at pH of 1.5 to 3. That’s very acidic! Believe it or not, low stomach acid is actually quite common, and one of the consequences of poor digestion, especially poor protein digestion, can be food allergies. More on that in the next post!

The next player in digestion in the pyloric sphincter. If the cardic sphincter is the gatekeeper above then the pyloric sphincter is the gatekeeper below. Except I like to think of it as a bouncer because it is *very* picky about who it lets through the door! If the chime is not acidic enough the pyloric sphincter will not allow it to pass in the small intestine, and with good reason!

Think of it this way. We’ve all had the experience of going out to dinner and to a party, and the next day we hear that some people got “food poisoning”. But some people…didn’t, even thought they ate the same food. Why? A likely reason is stomach acid. Stomach acid is the body’s first defense again food-borne pathogens. This was necessary for our survival, since things like health inspectors and proper food handling techniques are fairly new in the history of mankind. So if everyone had the same food but only some people got sick, the odds are that the ones who got sick had weak stomach acid which didn’t effectively kill whatever pathogen snuck into the food. Even though to pyloric sphincter is very insistent about not letting inappropriately acidified food past the gate, eventually, as time passes or more food enters the stomach, it has to empty the stomach and chaos ensues. More about that in the next post as well!

Here’s another problem with low stomach acid production—-it causes heartburn.

Wait, what?

I know, it’s counter-intuitive. We’ve be taught that the cause of heartburn or acid indigestion in too much stomach acid. The truth is, hyperchlorhydria (acid over-production) is actually quite rare. There is something much more simple that is probably going on, namely low stomach acid.

It all goes back to to the pyloric sphincter. Let’s say the the available stomach acid in your stomach is only able to bring the pH to 5. The pyloric sphincter is having none of that, it will cross it’s arms and not let any of that chyme into the small intestine. So the food sits there. And sits there. And sits there. Think about what would happen if you put a cooked chicken breast, some steamed broccoli and a baked potato in the blender, whipped it up and then let it sit it a hot, dark room. Yuck! It would start to rot pretty quickly. Rotting food starts to generate gas, the gas builds up and, with nowhere else to go, it breaks through the poor cardiac spincter, splashing up into the esophagus. And while a pH of 5 might not be enough to properly digest and sanitize food, it is definitely enough to burn your esophagus. Ouch!

So as you can see, stomach acid is incredibly important, and it’s one of the easiest things to go awry. If you tend to feel full for more than 2-3 hours after meals or you often have gas within an hour of eating or you have a lot of food and environmental issues, you probably have low stomach acid production. A simple solution is to drip a few drops bitters on your tongue or add them to a glass of water and sip it as you have your meal. The bitter taste will stimulate your stomach to produce more HCl. Some people supplement with betaine HCl supplements which are easily found at any health food store. Keep in mind—HCl is *not* for anyone who is on steroid therapy. If that’s the case for you, stick to the  bitters.

I’ll talk more about heartburn and acid indigestion, and especially the dangers of acid-blocking drugs, in another post. For now I’ll sign off, and I’ll see you in the next post where we’ll see what happens when the pyloric sphincter lets us behind the door into the wonderland that is the small intestine!