July 18, 2024

Is Slobber a Good Thing? Digestive Juices We Take for Granted

Author: Kate Findley
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By Roberta H. Anding, M.S., Baylor College of Medicine and Texas Children’s Hospital
Edited by Kate Findley, The Great Courses Daily

You don’t realize what you’ve got until it’s gone—this is especially true for basic bodily functions, like chewing. Professor Anding also explains why you should go easy on antacids and aspirin.

Close up of woman eating fruit on spoon
Digestive juices essential for processing food exist in saliva and in the stomach. Photo by Alliance Images / Shutterstock

Saliva: An Essential Digestive Juice

Most Americans have had a digestive disorder at some time during their lives, and according to the National Institutes of Health, between 60 and 70 million Americans are affected by digestive diseases. When it comes to our health, one thing we often take for granted is digestive juices. These juices are found in our mouths in the form of saliva and in our stomachs.

First, chewing our food breaks it up into smaller pieces, moistens the food, and introduces a compound called salivary amylase. Salivary amylase is an enzyme that digests carbohydrates. Words containing the last three letters “ase” indicate an enzyme, and an enzyme facilitates a bodily process. 

Take a piece of bread and hold it in your mouth. Don’t chew it or swallow it. The longer it stays in your mouth, the sweeter it gets. You’re taking a complex carbohydrate—bread—and breaking it into its smaller component pieces, and the smaller those pieces get, the sweeter they get.

Digestive disorders can occur when a person is not able to carry out this first step of the digestive process—breaking up food into smaller parts. For example, someone with head or neck cancer who’s had radiation ends up not being able to produce saliva, and thus they must seek out pre-moistened foods. 

Instead of eating an apple, they eat applesauce. When eating a potato, they should moisten the potato with either gravy, margarine, or artificial saliva.

After we chew our food, a series of one-way valves takes food from the beginning of the digestive system to the end. The esophagus is where we encounter that first one-way valve—a cardiac, meaning heart, because it’s close to the heart. When this goes wrong, we end up with gastroesophageal reflux disease (GERD), which occurs when stomach acid comes up into the esophagus, resulting in heartburn.

The Mighty Mucin Layer

The food then moves to the stomach, where satiety—that feeling of fullness—occurs. In the stomach, the food is churned and mixed up with digestive juices. 

Have you ever had the experience of being really hungry, and your stomach is grumbling? What’s happening is that the stomach is actually churning in the anticipation that hopefully food is on the way. 

The stomach is also highly acidic, and most of us view that acid as a bad thing. However, the stomach is unique; it is protected from its own acidic contents by what’s called a mucin layer—not mucus, but a layer that lines the stomach. This layer acts as a form of protective insulation in the stomach to prevent it from being autodigested, or digested by itself.

Stomach acid aids in the process of digestion. It takes bigger molecules and turns them into smaller pieces, and it also kills bacteria. 

We don’t think of bacteria as being in our GI tract, but some estimates suggest that we eat enough bacteria to make over 1,000 people sick every day. Why don’t we get sick, though? Part of the reason is that bacteria can’t live in a really acidic environment. 

Reconsider Antacids

The next time you decide to take an antacid for an upset stomach, consider the purpose of an antacid—it goes against acid. It raises the pH of the stomach from something very acidic to something basic. 

While antacids can provide temporary relief from nausea or heartburn, taking them on a regular basis can lead to long-term health issues. The acid in your stomach helps to activate or make both iron—a mineral—and thiamine—a B vitamin—more available to be absorbed. 

Thus, taking antacids regularly would deplete your body of these nutrients. Additionally, your mucin lining can be eroded by nonsteroidal, anti-inflammatory medications such as ibuprofen and aspirin. 

“In my world where I take care of athletes, when I have a male athlete who has iron-deficiency anemia, it’s almost always because he’s been taking too many anti-inflammatories,” Professor Anding said. “It’s worn down that mucin lining … and when it’s broken down, the acid can now attack that very vulnerable muscular lining in the stomach, and causes it to bleed. 

“There may be no pain associated with it. You certainly don’t see red blood when you go and have a bowel movement, but nonetheless, it is there and you can end up having some real significant problems with anemia.”

As it turns out, then, the digestive processes we take for granted—chewing—or write off as “bad”—stomach acid—are highly beneficial when it comes to absorbing essential nutrients from our food.

This article was edited by Kate Findley, Writer for The Great Courses Daily.

Professor Roberta H. Anding is a registered dietitian and Director of Sports Nutrition and a clinical dietitian at Baylor College of Medicine and Texas Children’s Hospital. She also teaches and lectures in the Baylor College of Medicine’s Department of Pediatrics, Section of Adolescent Medicine and Sports Medicine, and in the Department of Kinesiology at Rice University. In addition, she is a registered dietitian with the American Dietetic Association and a dietitian for the Houston Texans NFL franchise. 

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