Digestion for (not-so) Dummies: The Stomach, Pt.1

Tums, Rolaids, Nexium, the purple pill: if the stream of ads for medication to reduce stomach acid are to be believed, we’re in the midst of a serious epidemic of excessive stomach acid. We are absolutely drowning in the stuff and should all run to our doctors for prescription-strength drugs to lower it. How else could we account for the fact that over the counter and prescription medications to treat heartburn, GERD, and other forms of indigestion are among the top selling drugs of our time? Contrary to what we’ve been led to believe about these conditions, most effects of indigestion are due to too little stomach acid, not too much. Yes, you read that correctly. We are not awash in excess stomach acid. If anything, we’re starving for it.

If this sounds illogical, it’s only because many of us are unfamiliar with the anatomy and physiology of our own digestive tracts. It makes sense at first glance that too much stomach acid would cause the discomfort we associate with indigestion, but our primer on this part of the digestive process will reveal that rather than making our stomachs less acidic, we want to make sure our stomach acid is strong and abundant. When stomach acid is insufficient, indigestion is only one among myriad conditions that result. The list of health complications that can be tied directly or indirectly to low stomach acid stretches from acne to vitiligo, and if there were more common conditions with the letters W through Z, they’d be on the list, too.

So here we go…

Wooooo wooooo! All aboard! We started in the brain, went south to the mouth, and the digestion train is now departing for the esophagus and stomach! Wooooo wooooo!

The esophagus is pretty simple. It’s the pipe that runs between our mouth and stomach. When we swallow food, it travels down the esophagus until it drops happily into the stomach. Between the esophagus and the stomach is a circular muscle called the lower esophageal sphincter. (Because it’s a sphincter at the lower end of the esophagus. Nice, huh? Sometimes the people who name these things lob an easy one our way; usually not, though.) Most of the time, this sphincter stays closed. When food presses up against it from the bottom of the esophagus, it opens up to let that food enter the upper portion of the stomach. But things don’t just go one way here. The stomach can also send food back up into the esophagus and out the mouth. (If you’ve ever had the unfortunate experience of vomiting, you’ve experienced this firsthand. If not, you can conduct a little experiment for yourself. It involves cheeseburgers, chili cheese fries, and a lot of alcohol.) So yeah, normally, the sphincter only lets things go down. If things are coming back up, there’s a problem down below.

What’s down below? The stomach. The amazing, incredible sack of muscle that is capable of expanding and contracting like a balloon. And, much like the heart, the stomach has muscular contractions all on its own, without us having to tell it to contract. (Called “involuntary contractions” in the medical science world. And thank goodness for them. Imagine how much of our time we’d waste if we had to consciously tell our stomachs to churn or our hearts to beat. When would we ever have time to watch Chopped reruns on Food Network  read the latest research in peer-reviewed nutrition journals?) 

Here’s the deal with the stomach: it is indeed a sort of hollow pouch or sack, surrounded by a couple of layers of muscle. These muscles are responsible first for more of the mechanical breakdown of food in the stomach—literally the movement of the food this way and that, breaking it down into smaller pieces, kind of like a chewing process inside the stomach. As we mentioned in previous parts of this series, cells in the stomach also produce hydrochloric acid, or HCl, commonly known as stomach acid. HCl’s main job is to denature proteins. (Think about what lemon or lime juice does to seafood in a ceviche—the protein is “cooked” by the acid—transformed into a completely different state. That’s what HCl does.) Other cells lining the stomach secrete gastric lipase, which works on breaking down fats, but the vast majority of fat digestion doesn’t happen until we hit the small intestine. (FYI, most enzyme names end in –ase. Fats are also called “lipids,” hence the enzyme that breaks them down being called lipase. Just like the enzyme that breaks down the milk sugar, lactose, is called lactase.) There is very little breakdown of carbohydrates in the stomach; most of that also happens in the small intestine.

The second thing the contraction of stomach muscles does is assist with the chemical breakdown of food. While these muscles are movin’ and shakin’, so to speak, they combine the smaller bits of food with HCl and digestive enzymes. Think of it like a washing machine: the chewed up food mixes with stomach juices the same way your washing machine twists and turns, swishing dirty clothes around in soapy water. Remember what I said last time, when I talked about the mouth, and how important it is to chew. I said that sufficient chewing breaks the food down really well and gives the stomach a “head start.” The more you chew, the less work your stomach has to do in that department, and the more surface area there is for the HCl and enzymes to do their jobs.

Before we go any further, we should cover a nifty little factoid about stomach anatomy. We usually think of the stomach as one continuous sack. Technically speaking, it is. But within that sack are three main compartments: the fundus, the body, and the pylorus. Very little mechanical or chemical digestion happens in the fundus, which is the uppermost section. Food kind of hangs out there for a little bit, like people lined up outside the velvet rope, waiting their turn to get into an exclusive club. But the presence of food there (specifically, the presence of protein) sort of knocks on the door of the cells down below that produce HCl and enzymes, and says, “Hey there! We’ve got food here. You’d better get crackin’ on making some acid.”  

The bulk of the churning where all that great washing machine action happens is in the body, the largest part of the stomach. Note: this is why, as I mentioned in parts 1 and 2 of this series, it’s important to eat slowly. If you wolf your food down, hardly pausing to breathe between bites, your first few bites of food will still be sitting in the fundus while the whole rest of the meal comes tumbling in after. Now your stomach acid has to play catch up. It just barely heard the knock on its door and all of a sudden there are a thousand more people knocking. If you’ve ever had the sensation that food is sitting in your stomach like a brick for an hour or so after you’ve eaten, this is a likely culprit. SLOW. DOWN. (If you are so inclined, feel free to insert the words “the heck” in between those two.)

Okay. Moving along. Another substance secreted by cells lining the inside of the stomach (or “lumen,” to use anatomy geek-speak again) is mucus. You can think of it kinda like the stuff that comes out of your nose when you’re sick, but let’s stick to a more positive interpretation of its role: the mucus that lines the inside of the stomach is what protects the stomach muscles themselves from being digested by stomach acid. (Because those stomach muscles are made of protein, right? So think about what would happen if they were in direct contact with HCl. Not good.) This is also why chronic dehydration can cause stomach ulcers: the biggest component of this protective mucus is water. Not enough water means not enough mucus. Not enough mucus means stomach acid eating away at the stomach itself and burning a hole right through it!

The reason it feels like it’s burning is 

because it is. Burning the lining of your 

esophagus, that is!

The thing is, the esophagus does not have this protective mucosal coating, so when the lower esophageal sphincter (LES) opens up for some reason, and the acidic contents of the stomach go back up into the esophagus, it feels like burning. This is where the term “heartburn” comes from, even though, as you can see now, it has nothing to do with the heart. Anatomically speaking, the stomach and LES are higher than most people think they are, so it only seems like the pain is happening near the heart. The word “reflux” is a more fitting description, because the contents of the stomach are refluxing back upward.

Okay. Got it. So the question we should be thinking of next is, why does the LES open and let acidified stomach contents back into the esophagus, causing us to reach for the nearest jumbo-size tub of chalky, berry-flavored antacids? Lots of reasons. One is, oddly enough, pharmaceutical drugs! Here’s just a partial list of things the authors of this book call “LES weakeners”: Bronchodilators (like albuterol and ephedrine), NSAIDs (painkillers like aspirin & ibuprofen), calcium channel blockers and beta-blockers (used for high blood pressure), Valium, and Demerol. Also: cigarettes! A couple of foods are also said to weaken the LES: chocolate, coffee, peppermint & spearmint, onions, and alcohol. (Not that I think this is a reason to give up these things. After all, peppermint tea is also recognized for helping digestion, and onions have health benefits out the wazoo. If you don’t frequently experience reflux, I see little reason to stay away from the foods on that list.)

Don't try this at home.

What are some other reasons why that sphincter loosens up, allowing reflux to happen? Does it hate us? Did we do something to it in a former life? No. (Well, maybe you did, but I didn’t.) It’s all about stomach acid. Contrary to what all those ads would have us believe about stomach acid, the stomach is supposed to be acidic. Really acidic. In fact, a stomach at rest (i.e. not actively digesting food) should have a pH of between 1 and 3. (Note, for those of you who don’t remember high school chemistry: a pH of 7 is neutral. The lower the number, the more acidic. And it’s a logarithmic scale, so a pH of 6 is ten times more acidic than 7, and 5 is 100 times more acidic than 7. So a pH of 1-3 is pretty darn acidic, and that’s at rest!) Actual HCl in active digestion has a pH of around 0.8. That is some seriously strong acid, folks. When, for reasons we’ll get to soon, not enough stomach acid is being produced, or the stomach acid that is being produced is less acidic (or more alkaline) than it should be, it causes a MAJOR derailment of our happy little digestive train. When HCl is strong and abundant, the stomach breaks down food quickly and sends it along into the small intestine. But when there’s a lack of stomach acid, or acid that’s too alkaline, food stays in the stomach longer than it’s supposed to. This is the train that gets stuck at the station and causes problems both ahead and behind. The problem it causes behind is reflux. When foods—carbohydrates, in particular—stay in the stomach longer than they should, they start to ferment. This results in bubbles and gas (think of grains fermenting to make beer, although the fermentation process is a little different), and it is this bubbling gas that refluxes back into the esophagus. It has nothing to do with too much stomach acid. Raise your hand if you didn’t know that! And remember: even though this food & acid mixture is less acidic than it should be (because of decreased acid), it’s still far more acidic than anything the esophagus is designed to handle, especially considering it has no protective mucus. So that’s why we get that burning sensation.

There are many more things that can go wrong from low stomach acid to result not just in reflux/GERD, but in a laundry list (dirty laundry, at that!) of health complications that range from the mildly irritating to the downright deadly. We’ll get to the details next time.

But before we’re finished for the day, we should probably talk about what causes low stomach acid in the first place, right? Because if we know we want lots of it, and we want it to be strong, we need to know what makes it decrease and weaken.

Easy-peasy. Go back to part 2 of this series, where we talked about the brain, and how being stressed out, in a hurry, angry, or otherwise experiencing negative emotions keeps our fight-or-flight mechanism dominant, and gives our nice, calm, rest-and-digest parasympathetic nervous system a kick in the jimmies. Our modern, stressful, go-go-go lives are a recipe for low stomach acid. Also: eating in a rush. Remember, digestion is like a well-orchestrated symphony: our bodies have to get the right signals at the right time and all the players have to do their part. If we eat in a hurry and then rush off to the next meeting or to pick up the kids, the majority of that food will be inside the stomach before the stomach has even registered that there is food there. The stomach acid catch-up game begins, and guess what? Yep, that food will now sit in the stomach longer than it otherwise would. And we know what happens next.

And a third thing that can cause low stomach acid iiiiiiiiiiiiizzz…

ANTACIDS!  Ding ding ding! Prescription and OTC antacids neutralize whatever little stomach acid our bodies do manage to produce during our hurried and over-stressed mealtimes. Just when we should be supporting more stomach acid, we do the opposite. The calcium and other alkaline ash minerals in antacids serve as buffers against the acidity we feel “burning” our esophagus. And yes, the burning subsides, but this is a short-term band-aid, not a solution to the underlying cause of the situation.

Prescription acid blockers are like antacids on crack. See, chewable antacids buffer the acid that’s already been produced. It doesn’t alter anything at a cellular level or mess with human physiology. (If you’re into crime dramas, think of them as “accessories after the fact.”) But prescription acid blockers actually prevent the secretion of acid in the first place. (Ever heard acid blockers referred to as “PPIs” or “proton pump inhibitors?” They get that name because they inhibit the teeny, tiny pumps embedded in stomach cells that are supposed to push protons [actually, hydrogen ions, H⁺, or acid] into the lumen of the stomach.) If we know anything about digestion—and we’re certainly beginning to piece together the puzzle—this is the last thing we’d want to do to ensure good digestion. Oh, those kooky modern medical standards. They get me every time!

This is the best modern medicine has to offer you. Pathetic.
And a darn shame!
(We'll cover natural heartburn remedies in an upcoming post.) 

So now that we know reflux is not the result of excess stomach acid, and that we actually want to increase stomach acidity, how do we fill that tall order? Stay tuned for next time. We’ll also go over some other consequences of low stomach acid, most of which will make reflux look like a walk in the park.

For a great recap of all this, check out these two posts from Balanced Bites:

Why You Want More Stomach Acid, Not Less

Troubleshooting Your Digestive Issues – Part 1

And this amazing series by Chris Kresser. (It’s 6 parts, but the real bang for your buck is in the first 3-4. And he’s much more succinct than I am. Well worth your time to read if you ever experience reflux, bloating, or gas!)

What Everybody Ought to Know but Doesn’t about Heartburn & GERD

Continue to the next post: Stomach, part 2.





Remember: Amy Berger, M.S., NTP, is not a physician and Tuit Nutrition, LLC, is not a medical practice. The information contained on this site is not intended to diagnose, treat, cure, or prevent any medical condition.