Which dietary ingredients (e.g., berberine, probiotics) have peer‑reviewed evidence of increasing endogenous GLP‑1 secretion in humans?

1. Protein — the most robust human signal, especially whey

Multiple reviews and a meta‑analysis identify dietary protein as a reproducible stimulator of postprandial GLP‑1 in humans, with whey protein studied most extensively and shown to increase GLP‑1, slow gastric emptying and raise insulin in clinical trials ^{[1] [4]}.

2. Soluble, fermentable fiber — raises GLP‑1 via colonic SCFAs in human trials

Human intervention data and reviews report that soluble fibers (for example pectin and barley‑based or other fermentable fibres) increase colonic short‑chain fatty acids like acetate and propionate, which bind L‑cell receptors (FFAR2/3) and have been associated with higher circulating GLP‑1 and improved postprandial glycemic control in randomized studies ^{[5] [4] [6]}.

3. Dietary fats and Mediterranean patterns — unsaturated fats outperform saturated fats

Controlled human comparisons of olive‑oil–rich (MUFAs) meals versus butter (SFA) meals produced larger post‑meal GLP‑1 responses, and narrative reviews conclude diets richer in MUFAs or omega‑3 PUFAs may increase GLP‑1 secretion versus saturated‑fat‑rich diets ^{[6] [4] [7] [3]}.

4. Probiotics and microbiota interventions — mechanistic promise, inconsistent human results

Preclinical and some small human studies show certain probiotics or prebiotic fibers can change microbiota composition, boost SCFAs and stimulate L‑cell GLP‑1 release, yet systematic reviews of randomized human trials find the probiotic/prebiotic evidence inconclusive for reliably raising GLP‑1 or producing weight effects ^{[8] [2] [9]}.

5. Berberine and polyphenols (curcumin, quercetin, resveratrol) — mostly preclinical or small trials, not definitive in humans

Mechanistic and animal studies indicate berberine and various polyphenols can modulate GLP‑1 pathways or inhibit GLP‑1 degradation enzymes in vitro, and small human metabolic studies hint at glucose‑lowering benefits, but peer‑reviewed human trials demonstrating consistent increases in endogenous GLP‑1 are lacking or limited in scale and quality ^{[6] [9] [10] [11]}.

6. What the reviews say about strength and limits of the human evidence

Multiple narrative and systematic reviews emphasize that while single‑meal and short‑term trials suggest higher protein, soluble fiber and unsaturated fats can raise postprandial GLP‑1, the body of randomized, longer‑term human trials is sparse, heterogeneous and sometimes contradictory — for example, six trials of prebiotic/probiotic/synbiotic interventions produced mixed results, and many studies combine nutrients so isolating single‑ingredient effects is difficult ^{[2] [4] [8]}.

7. Practical reading: what is peer‑reviewed and actionable versus speculative

Peer‑reviewed human data best support whey/other dietary proteins, soluble fermentable fibers (e.g., pectin, certain cereal fibers) and dietary patterns rich in MUFAs/PUFAs like Mediterranean diets for modest increases in endogenous GLP‑1 and related metabolic benefits; probiotics, berberine and polyphenols remain plausible adjuncts but should be considered experimental for the explicit goal of increasing GLP‑1 until larger, well‑controlled human trials are published ^{[1] [5] [3] [9] [10]}.

8. Bottom line and research gaps

Endogenous GLP‑1 can be nutritionally modulated in humans, but certainty varies: protein, fermentable soluble fiber and unsaturated‑fat dietary patterns have the strongest human peer‑reviewed backing, while probiotics and botanical supplements show mechanistic or animal promise but inconsistent human evidence; definitive guidance awaits larger, standardized human interventions that measure GLP‑1 kinetics and clinically relevant outcomes ^{[1] [5] [2] [4]}.