A systematic review and meta-analysis published in Clinical Nutrition ESPEN found no evidence that peptide-based enteral formulas reduce diarrhea in hospitalized adults receiving tube feeding. The finding goes directly against a common clinical habit, since guidelines suggest switching from a polymeric formula to a more expensive peptide-based one when diarrhea appears.

The two formula types differ in how the protein arrives. Polymeric formulas use intact protein, while peptide-based formulas use protein that has already been hydrolyzed into shorter fragments, on the theory that partially broken-down protein is easier for a compromised gut to absorb.

Key results

The authors screened 3,196 records and included 27 randomized trials, of which 12, covering 914 participants, reported diarrhea. Pooled across those trials, the risk ratio was 0.89 with a 95% confidence interval of 0.53 to 1.52, heterogeneity of 64%, and very low certainty on GRADE.

Mortality showed no clear difference either, at a risk ratio of 0.82 (95% CI 0.53 to 1.24) across 11 trials, again rated very low certainty. Other gastrointestinal outcomes were too sparsely reported to pool.

The pectin signal

The one apparently favorable result came from two open-label trials of pectin-containing formulas, at high risk of bias, with a risk ratio of 0.34 (95% CI 0.14 to 0.78). In the other nine trials the estimate ran the other way, at 1.25 (95% CI 0.84 to 1.85), with a subgroup difference of p = 0.006.

The authors are blunt that this is exploratory, imprecise, and cannot be attributed to the peptide itself. Dropping high risk of bias trials pushed the overall estimate to 1.12 (95% CI 0.67 to 1.88), and the review says a possible increase in diarrhea with some peptide-based formulas cannot be excluded.

Limitations

Screening, eligibility, extraction and risk-of-bias assessment were performed by a large language model rather than duplicated by human reviewers, and the authors report this as the review's principal limitation. Every excluded record went through a second independent model pass, every extracted item was tied to a verbatim quotation, and the authors verified each item entering the analyses against source documents.

Embase was not accessible during the search, and the subgroup analyses by formula composition were post hoc. Certainty was very low for both main outcomes.

Where this leaves the guideline

The conclusion is that randomized evidence does not show a diarrhea benefit for peptide-based formulas, at very low certainty. Whether the guideline switch survives that is now a question for whoever writes the next version.