---
type: source
title: "GLP-1 Micronutrient Deficiencies: Narrative Review of 6 Studies (n=480,825) — Iron, Calcium, Vitamin D, Protein Deficits Systematic"
author: "Urbina et al., Clinical Obesity (Wiley)"
url: https://onlinelibrary.wiley.com/doi/10.1111/cob.70070
date: 2026-01-01
domain: health
secondary_domains: []
format: research-paper
status: unprocessed
priority: high
tags: [GLP-1, micronutrients, nutritional-deficiency, iron, calcium, vitamin-D, protein, semaglutide, safety, monitoring]
---

## Content

Systematic narrative review of micronutrient and nutritional deficiencies associated with GLP-1 receptor agonist therapy. Structured PubMed and Cochrane search (January 2019 – May 2025), 6 studies meeting inclusion criteria, encompassing 480,825 adults.

**Key quantitative findings:**

- **Vitamin D**: 7.5% deficiency at 6 months, 13.6% at 12 months. Mean vitamin D intake of 4 μg/day — significantly lower than estimated national average of 19 μg/day. Only 1.4% of GLP-1 users met 100% of the Dietary Reference Intake (DRI) for vitamin D.

- **Iron**: GLP-1 users demonstrate 26–30% lower ferritin levels than SGLT2 inhibitor comparators. 64% of GLP-1RA users consumed below the estimated average requirement (EAR) for iron. Iron absorption drops markedly after 10 weeks of semaglutide (prospective pilot, n=51).

- **Calcium**: 72% of users consumed below the Recommended Dietary Allowance (RDA) for calcium.

- **Protein**: 58% did not meet recommended protein intake targets (1.2–1.6 g/kg/day during active weight loss per OMA/ASN guidance).

- **Thiamine and cobalamin**: Deficits increase over time (consistent pattern).

**Mechanism**: GLP-1-induced appetite suppression is non-selective — it reduces total caloric intake including micronutrient-rich foods. Delayed gastric emptying alters absorption kinetics. The drugs do not distinguish between "calories to reduce" and "nutrients to maintain."

**Clinical implication stated by authors**: "Micronutrient deficiencies during GLP-1RA therapy are a common consequence rather than a rare adverse effect."

**Monitoring gap**: 92% of patients had no dietitian visit in the 6 months prior to GLP-1 prescription (from complementary study). Multi-society advisory (OMA/ASN/ACLM/Obesity Society) recommends proactive nutritional monitoring and supplementation but protocol adoption lags at scale.

## Agent Notes

**Why this matters:** This is the systematic literature synthesis confirming that what was seen in single large cohorts is robust across studies. The n=480,825 across 6 studies means this isn't one health system's data — it's a meta-level confirmation of the nutritional deficiency pattern. The framing — "common consequence, not rare adverse effect" — should change how GLP-1 prescribing infrastructure is designed.

**What surprised me:** The 1.4% vitamin D DRI compliance figure. This means 98.6% of GLP-1 users are NOT meeting vitamin D intake needs through diet. Combined with already-high population-level vitamin D deficiency rates (approximately 40% in the US generally), GLP-1 users are starting from a disadvantaged baseline and making it significantly worse. This is not a marginal nutritional concern — it's near-universal.

**What I expected but didn't find:** Any stratification of deficiency rates by socioeconomic status, food security, or Medicaid vs. commercial insurance status. The review analyzed GLP-1 users generally — no breakdown for the food-insecure population where baseline micronutrient deficiency is already elevated. The food-insecure + GLP-1 double-jeopardy remains an inference, not a direct measurement (see research gap note in Session 21).

**KB connections:**
- Supplements and extends: existing archive `2026-04-08-glp1-nutritional-deficiency-signal.md` (different source, overlapping findings but broader systematic methodology)
- Reinforces the monitoring infrastructure argument: if 64% iron-deficient, 72% calcium-deficient, 58% protein-deficient — the software layer providing dietary tracking becomes medically essential
- Directly relevant to the OMA/ASN/ACLM advisory already archived: the advisory was right to flag nutritional monitoring as essential infrastructure
- Connects to atoms-to-bits argument: continuous dietary monitoring alongside GLP-1 delivery is the natural moat position

**Extraction hints:**
- Primary claim: "GLP-1 receptor agonist therapy produces systematic micronutrient deficiencies in the majority of users — 64% iron-deficient, 72% calcium-deficient, 58% protein-deficient — with only 1.4% of users meeting vitamin D dietary requirements, making nutritional monitoring infrastructure a clinical necessity not an optional enhancement"
- Note scope carefully: "common consequence, not rare adverse effect" is the claim's core precision
- The 1.4% vitamin D compliance figure is the most concrete single datum for the headline claim

**Context:** Urbina et al. published in Clinical Obesity (Wiley), a peer-reviewed journal of the World Obesity Federation. The narrative review methodology is appropriate for synthesizing heterogeneous study designs. The 6-study cutoff is a limitation — this is a rapidly evolving field — but the convergence across studies strengthens the directional conclusion.

## Curator Notes (structured handoff for extractor)

PRIMARY CONNECTION: Existing `2026-04-08-glp1-nutritional-deficiency-signal.md` archive + OMA/ASN advisory archive
WHY ARCHIVED: Systematic multi-study synthesis (not a single cohort) confirming nutritional deficiency as a common consequence. The framing upgrade — "common consequence, not rare adverse effect" — elevates this from a signal to a clinical fact requiring infrastructure response.
EXTRACTION HINT: Claim should emphasize the near-universality of specific deficits (iron: 64%, calcium: 72%, vitamin D: 98.6% not meeting DRI) rather than just prevalence statistics. The monitoring gap (92% no dietitian visit) is the infrastructure claim that follows.
