GLP-1 Receptor Agonists

WHAT IT DOES

GLP-1 receptor agonists mimic glucagon-like peptide-1, an incretin hormone released by the gut after a meal. Three effects matter for anyone taking supplements alongside them. First, central appetite signaling changes: hunger falls, fullness and satiety rise, and total energy intake drops substantially, by roughly 39 percentage points relative to placebo in a randomized trial measuring ad libitum energy intake at a test meal (Gabe 2024, PMID: 39082206). Second, gastric emptying slows, which flattens postprandial glucose but also changes the rate at which anything swallowed reaches the small intestine (Jalleh 2024, PMID: 39568409). Third, insulin secretion becomes more glucose-dependent and glucagon is suppressed, which is why these agents carry low intrinsic hypoglycemia risk on their own but amplify it when stacked on insulin or a sulfonylurea (Filippatos 2015, PMID: 26177483).

The supplement-relevant consequence follows from the first two. A much smaller total food volume means a much smaller total micronutrient intake, and slowed gastric transit plus reduced gastric acid secretion changes absorption conditions for minerals that need an acidic environment, iron in particular (Infante 2026, PMID: 42451041). The deficiency risk here is mostly a dilution problem driven by eating less, not a direct blockade by the drug.

One nuance worth knowing: gastric emptying delay is not necessarily permanent. It appears strongest early and after dose escalations, and in a 20-week randomized study of once-daily oral semaglutide at 50 mg no statistically significant difference in gastric emptying remained at week 20 despite continued appetite and weight effects (Gabe 2024, PMID: 39082206). Timing advice that made sense in month one may be less relevant in month six.

SAFETY PROFILE

Critical Interactions (Do Not Combine Without Medical Supervision)

Moderate Interactions (Monitor Closely)

Theoretical/Low-Risk Interactions