Metabolic & Cardiometabolic
ileal nutrient delivery increases GLP-1 secretion
📅 Last reviewed: 2026-08-11 ⓘ
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: Human trials (RCT / n-of-1)
How the studies fall
What the evidence shows
The 'ileal brake'. Directly tested in humans by infusing nutrient into the terminal ileum through a catheter or ileostomy, which is about as clean a test of the mechanism as is ethically available. Consistent and sizeable: even 30 cm of ileum exposed to glucose produces substantial GLP-1 release, and the response tracks active glucose absorption.
The evidence (4)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Wen J, et al. 1995 · The American journal of physiology | animal | supports | moderate | Canine ileal/colonic perfusion with nutrient raised plasma PYY and GLP-1 and delayed duodenal migrating motor complexes, establishing the peptide basis of the ileal brake. Dog. |
| van Avesaat M, et al. 2015 · International journal of obesity (2005) | RCT | contradicts | moderate | Randomized single-blind crossover, n=13 healthy lean adults, naso-ileal catheter, 90-min ileal infusion of safflower oil / casein / sucrose vs saline. GLP-1 did NOT rise: 'Secretion of cholecystokinin and peptide YY but not of glucagon-like peptide-1 (7-36) was increased during ileal perfusion of fat, carbohydrates and protein.' The ileal brake itself fired -- food intake fell for all three macronutrients (HC 399.0+/-57.0, HP 458.0+/-78.6, HL 464.3+/-90.7 vs control 586.7+/-70.2 kcal, P<0.005 to P<0.0001) -- but via CCK/PYY, not measurable active GLP-1. Directional null on an 'increases' claim = contradicts (CONVENTIONS 2026-06-29 rule). Caveat: active GLP-1(7-36) assay, n=13, abstract-grade read. |
| van Avesaat M, et al. 2017 · International journal of obesity (2005) | RCT | supports | moderate | Double-blind randomized placebo-controlled crossover, n=14 healthy lean adults (mean BMI 21.6), naso-ileal catheter; 15 g protein infused over 60 min into duodenum, jejunum or ileum vs placebo. Direct on-claim result: 'GLP-1 concentrations were increased after ileal infusion compared with jejunal and placebo infusion, whereas CCK concentrations were only increased after intraileal protein infusion compared with placebo.' Ileal infusion also cut the next meal (ileum 628.5+/-63 kcal vs duodenum 733.6+/-50 kcal, P<0.01; vs placebo 712.2+/-53 kcal, P<0.05). Scope limits stated by the paper: 'None of the treatments affected VAS scores for hunger and satiety nor plasma concentrations of PYY and glucose.' Delivery was intraluminal catheter infusion, not oral intake. |
| Zhang X, et al. 2022 · Metabolism: clinical and experimental | RCT | supports | high | Double-blind randomized crossover, n=10 with loop ileostomy. 30 g glucose infused into 30 cm of terminal ileum produced substantial increases in plasma GLP-1 vs saline, with only minimal changes in glucose/insulin/C-peptide and no change in ghrelin, GIP or glucagon. GLP-1 response strongly related to active glucose absorption (serum 3-OMG). NCT05030376. |
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