Low stomach acid is called hypochlorhydria. In Gut and Physiology Syndrome, Dr. Natasha Campbell-McBride explains how reduced acidity can interfere with the first steps of protein digestion and add to problems further along the intestine.[1]
It helps to follow one meal through the sequence instead of treating low acid, an enzyme shortage and a damaged intestinal lining as the same problem.
The First Step Is in the Stomach
Stomach acid provides the conditions for pepsin to begin breaking down dietary proteins. The book gives a pH of 3 or below for pepsin’s work. When acid production is low, that first stage of protein digestion may be less effective.[1]
Campbell-McBride describes toxins from pathogenic microbial overgrowth as suppressors of acid secretion. She also discusses acid-suppressing medicines in the same chapter. This is her account of why stomach acidity belongs in the GAPS digestion discussion.[1]
Why Gluten and Casein Receive Attention
The author uses gluten from grains and casein from milk as extensively researched examples. In her explanation, incomplete digestion produces peptides including casomorphins and gluteomorphins, also called gliadomorphins. She discusses their opioid-like activity and proposed effects after absorption through a damaged gut wall.[1]
The newer book also says the issue extends to other food proteins. Gluten and casein are examples in the explanation, rather than proof that every digestive problem is solved by removing two ingredients.
The Intestinal Lining Has More Work to Do
Proteins leaving the stomach continue to be digested by pancreatic and intestinal enzymes. Enterocytes are the cells lining the intestine. Their brush-border peptidases help split peptide chains into amino acids for absorption.[1]
Campbell-McBride describes two connected difficulties when those cells and the gut flora are unhealthy: peptide digestion can remain incomplete, and the damaged barrier can allow incompletely digested material through.[1] Those are different steps, even when the book discusses them together.
| Step | Question It Answers |
|---|---|
| Stomach acid and pepsin | How does protein digestion begin? |
| Pancreatic and intestinal digestion | How is the protein broken down further? |
| Enterocyte peptidases | How is peptide breakdown completed at the intestinal lining? |
| Intestinal barrier | What is allowed to pass into the body? |
Acid Is Part of a Coordinated Response
The 2020 chapter connects stomach acidity with the duodenal hormones secretin and CCK, pancreatic bicarbonate, enzymes and bile. The hormones have different triggers. Acid is important for secretin, while fat and protein digestion products stimulate CCK.[1][3]
This means low acid should not be translated into “the pancreas produces nothing” or “every part of digestion stops.” The hormone guide explains the individual jobs without collapsing them into one switch.
The Psychology Book’s Weaning Example
The expanded Gut and Psychology Syndrome book uses weaning as an example of changing digestive demands. It names casein in follow-on formula and gluten in common grain foods as proteins that can arrive when stomach-acid production is already suppressed. Its discussion includes Candida toxins and maternal microbial toxins in breast milk as parts of the author’s explanation.[2]
This passage explains her proposed mechanism; it is not a GAPS first-food menu or a reason to assume a breastfed baby has low stomach acid. Our digestive-symptoms-around-weaning guide covers that context, and the Baby GAPS first-food guide gives the actual feeding sequence.
Does This Affect More Than Gluten and Casein?
Yes. The 2020 book describes broader protein maldigestion, along with possible consequences for nutrient absorption, allergies and autoimmune reactions. It gives gluten and casein particular attention without limiting the whole problem to them.[1]
Belching, bloating or another symptom alone does not establish stomach-acid levels or show that a particular peptide has crossed the intestinal wall. Keeping the mechanism distinct from an individual conclusion makes your notes more useful.
Choose the Next Part You Need
Use the stomach acid and pepsin guide for normal digestion, the DPP-IV guide for the later enzyme step, and the cabbage-juice guide for the author’s food-based options.
If you are recording foods, symptoms or product changes, the Die-Off & Reaction Log is listed in my WFLI Shop. A dated record can describe what happened without assigning a cause that the observation cannot establish.
References
- Campbell-McBride, N. Gut and Physiology Syndrome (2020), protein-digestion and enterocyte discussion; “Digestive Enzymes,” low acidity, microbial effects and digestive consequences.
- Campbell-McBride, N. Gut and Psychology Syndrome, expanded edition (2013), checked in the second German edition (2015), “Opiates From Gluten and Casein”, stomach acidity, Candida/maternal toxin account and weaning example.
- Liddle, R. A., et al. Cholecystokinin bioactivity in human plasma: molecular forms, responses to feeding, and relationship to gallbladder contraction. Journal of Clinical Investigation 75 (1985): 1144–1152. DOI:10.1172/JCI111809.
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