Peptidases do more than help digest food. In the expanded Gut and Psychology Syndrome book, Dr. Natasha Campbell-McBride describes another role: breaking down the body’s own active substances after they have done their work. Her peptidase-inhibition discussion concerns dietary peptides interfering with that process.[1]
This is a different question from “How does my meal get digested?” Keeping the two jobs separate makes a dense part of the book easier to follow.
Start With a Peptide
A peptide is a chain of amino acids. During digestion, larger dietary proteins are broken into smaller pieces. The 2020 physiology book describes enterocyte brush-border peptidases helping complete that work before absorption.[2]
The Psychology book also discusses peptide-based substances made inside the body. Its examples include neurotransmitters, hormones and other active substances that need to be broken down after performing their jobs.[1]
Two Jobs for Peptide-Digesting Enzymes
| Context | What Is Being Broken Down? | Why It Matters Here |
|---|---|---|
| Food digestion | Peptides produced from dietary protein | The intestinal lining helps complete protein breakdown. |
| Handling active substances in the body | The body’s own peptide-based messengers and other active substances | The Psychology book describes enzymes clearing them after their work. |
These are related enzyme activities, not two descriptions of the same location or step. The enterocyte brush border is part of food digestion. The inhibition passage goes on to discuss effects after dietary peptides have entered the body.[1][2]
What the Book Means by Inhibition
The expanded Psychology book says some dietary protein is absorbed as peptides, or even unchanged. It describes those incoming peptides as inhibitors of peptidases that handle the body’s active substances. In its GAPS explanation, an excessive incoming load can suppress that enzyme work.[1]
Campbell-McBride describes the result as an accumulation of fragments from the body’s own peptides. She connects that accumulation with damage and psychological symptoms. This is the mechanism she is proposing in this passage, rather than a claim that every absorbed peptide causes the same outcome.[1]
How This Differs From Opioid-Like Peptides
The books also discuss casomorphins and gluteomorphins from incompletely digested casein and gluten. In that discussion, the peptides have opioid-like activity. In the inhibition discussion, the issue is dietary peptides interfering with enzymes that break down the body’s own active substances.[1][2]
Both belong to the author’s wider account of incomplete digestion and a damaged intestinal barrier. They should not be combined into a single claim that one peptide explains every neurological or psychological symptom.
Why the 2020 Book Goes Beyond Two Proteins
The physiology book keeps gluten and casein as extensively researched examples, while explaining that other food proteins can also be incompletely digested and absorbed as peptides. It gives particular attention to difficult-to-digest plant proteins.[2]
That discussion supplies a reason to look at the whole digestive sequence. It does not create a new rule to remove every protein food, or to exclude every plant food from every GAPS approach. The GAPS food list is the place to check actual food permissions.
What This Explanation Can Help You Understand
The books connect food selection with the condition of the digestive system. Removing a food changes what enters the gut; supporting digestion and the intestinal lining concerns how food is handled. Those are complementary parts of the GAPS account, rather than competing explanations.
A symptom record cannot measure peptidase inhibition. It can still record the food, timing and changes you noticed. Keep that observation separate from a mechanism you have read about, so the notes remain an accurate account of what actually happened.
The Die-Off & Reaction Log is listed in my WFLI Shop for those dated observations. The Intro-versus-Full guide can help you connect the reading with an actual starting approach.
For the named digestive enzyme, read the DPP-IV and peptidase guide. For the earlier stomach step, continue with low stomach acid and protein digestion.
References
- Campbell-McBride, N. Gut and Psychology Syndrome, expanded edition (2013), checked in the second German edition (2015), “Opiates From Gluten and Casein”, dietary peptides, peptidase inhibition and accumulation of endogenous peptide fragments.
- Campbell-McBride, N. Gut and Physiology Syndrome (2020), protein digestion, enterocytes, gluten/casein peptides and other food proteins.
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