Benefits
Enzyme blends and AN-PEP (not DPP-IV alone) may ease non-celiac gluten sensitivity symptoms
The gluten-degrading enzyme in this space is AN-PEP (Aspergillus niger prolyl endoprotease, branded Tolerase G), which is NOT a DPP-IV: it is a prolyl endoprotease that cuts the internal immunogenic bonds of gluten and stays active at stomach pH. A 2015 RCT (Salden et al., Aliment Pharmacol Ther, 12 healthy volunteers) showed AN-PEP lowered gliadin levels in the stomach and duodenum after a gluten meal. That is AN-PEP evidence, not DPP-IV evidence. The only human trial in non-celiac gluten sensitivity (Ido 2018) used a multi-enzyme combination, not pure DPP-IV, and DPP-IV on its own has not been shown to break down immunogenic gluten effectively. Important caveat: this is supportive only — strict gluten avoidance remains the standard for celiac disease.
Casein peptide breakdown for dairy sensitivity
DPP-IV breaks down casomorphin peptides from milk casein digestion. Casomorphins (especially β-casomorphin-7 from A1 dairy) have been associated with GI sensitivity and possibly behavioral effects in some sensitive populations. No human trial has shown DPP-IV reduces dairy or casein symptoms. The casomorphin and behavioral claims rest on mechanism and observation, not on controlled trials, so any added benefit over lactase alone is only theoretical (lactase only addresses lactose, not casein peptides).
Accidental cross-contamination (pure DPP-IV not shown to protect)
For non-celiac individuals on a gluten-free diet (autoimmune Hashimoto's, eczema, IBS-D, etc.) who experience occasional accidental gluten exposure (restaurant cross-contamination, hidden gluten), there is no controlled evidence that pure DPP-IV reduces symptoms. The studies showing reduced gluten peptide levels after exposure used AN-PEP, a different enzyme, not DPP-IV. Critical: this is not safe for celiac patients, who require absolute gluten avoidance to prevent intestinal damage.
Improved digestive comfort in mixed-food sensitivity
When included in broad enzyme blends, DPP-IV contributes to comprehensive protein digestion and may support post-meal digestion, but no controlled human trial has tested pure DPP-IV for general food sensitivities or for so-called leaky gut.
Mechanism of action
Cleavage at proline-containing peptide bonds
DPP-IV specifically cleaves peptide bonds where proline (or alanine) is in the second position from the N-terminus (i.e., X-Pro or X-Ala dipeptides). Gluten and casein contain unusually high proline content (gluten ~15%, casein 11%), creating proline-rich peptides resistant to most other proteases. This is why these peptides survive normal digestion and can trigger immune reactions in sensitive individuals.
Tolerase G (AN-PEP) is a different enzyme, not DPP-IV
AN-PEP (Aspergillus niger prolyl endoprotease, branded as Tolerase G) is the most clinically-studied gluten-digesting enzyme, but it is NOT a DPP-IV. Its prolyl endoprotease activity cleaves internal proline bonds in immunogenic gluten peptides, particularly the 33-mer alpha-gliadin peptide implicated in celiac disease pathology. Acid-stable and active in stomach (pH 2-5).
Acid stability for stomach activity
AN-PEP is stable and active at gastric pH 2 to 5, so it begins breaking down gluten immediately in the stomach. Pure DPP-IV is different: it has a near-neutral pH optimum and is poorly active in the acidic stomach, so much of a gluten load can pass before it acts. This is a key reason DPP-IV alone is a weak gluten-degrading enzyme, and it begins working only where pH allows. AN-PEP’s acid stability is its main advantage over neutral-pH-only enzymes such as DPP-IV.
Clinical trials
Salden BN et al. 2015, Aliment Pharmacol Ther 42(3):273-285: randomized, double-blind, placebo-controlled crossover in 12 healthy volunteers given 4 g gluten with AN-PEP or placebo infused into the stomach. AN-PEP is a prolyl endoprotease, NOT a DPP-IV, so this trial does not test pure DPP-IV. DSM-affiliated authors (DSM makes AN-PEP).
12 healthy (non-celiac, non-sensitive) volunteers, gluten delivered directly into the stomach by catheter.
AN-PEP markedly lowered gliadin concentrations in the stomach and duodenum after a gluten meal versus placebo in healthy volunteers. These are results for AN-PEP (a prolyl endoprotease), not for DPP-IV, and they measure peptide levels, not symptoms or protection against celiac damage. Critical caveat: AN-PEP is not a treatment for celiac disease — it cannot reliably eliminate ALL gluten peptides and should not be used to enable gluten consumption in celiac patients. Position: may be useful for accidental cross-contamination management, not for daily gluten consumption.
Ullah H et al. 2023, Biomed Pharmacother 169:115858: randomized, double-blind, placebo-controlled trial in 120 functional dyspepsia patients given a fungal multi-enzyme blend or placebo for 2 months. The blend is not pure DPP-IV, the published report does not specify DPP-IV content, and functional dyspepsia is a different indication from gluten or casein sensitivity.
Functional dyspepsia patients. 60-day intervention.
The multi-enzyme blend improved dyspepsia quality-of-life, pain and sleep scores versus placebo over 2 months. This trial is for functional dyspepsia, not gluten or casein sensitivity, and no DPP-IV-specific effect can be isolated. It is borrowed evidence for a different indication.