Does reduced gastric acid from H. pylori or PPIs impair non‑heme iron absorption?

The interaction between gastric physiology and iron homeostasis is well-documented, with gastric acid serving as a critical mediator for the bioavailability of non-heme iron. When this environment is disrupted by infection or medication, it often results in a characteristic iron-deficiency profile.

Mechanistic Role of Gastric Acid

The stomach's highly acidic environment (pH 1.5–3.5) is essential for the initial dissolution of non-heme iron from dietary sources.

• Solubilization: At a pH below 4, iron solubility can reach approximately 35%, compared to just 3% in neutral environments. This prevents ferric iron (Fe³⁺) from precipitating as insoluble hydroxides.
• Preparation for Uptake: Maintaining iron in a dissolved state is a prerequisite for its reduction to the ferrous form (Fe²⁺), which is the specific substrate required for transport via Divalent Metal Transporter 1 (DMT1) in the duodenum.

Impact of Hypochlorhydria

Conditions that suppress gastric acid—hypochlorhydria—directly impair the body's ability to process dietary iron.

• Proton Pump Inhibitors (PPIs): Long-term use of PPIs is significantly associated with iron deficiency. Research indicates odds ratios for deficiency ranging from 1.96 to 3.58 among chronic users, with the risk increasing in a dose-dependent manner.
• H. pylori Gastritis: Infection with H. pylori can cause chronic gastritis that limits acid production. Meta-analyses demonstrate that eradicating the bacteria significantly improves hemoglobin and ferritin levels, often more effectively than iron supplementation alone.

Clinical Presentation and Laboratory Markers

When iron absorption is impaired due to low gastric acidity, the body typically exhibits a classic iron deficiency profile.

• Serum Markers: Patients frequently show low serum iron levels and depleted ferritin (iron stores).
• Compensatory Response: In response to low circulating iron, the liver increases the production of transferrin to maximize transport capacity. This is clinically reflected as an elevated Total Iron Binding Capacity (TIBC).
• Contextual Variation: While high TIBC is the standard response to malabsorption, chronic inflammation—such as that seen in active H. pylori infections—can sometimes blunt this increase, as inflammation may suppress transferrin synthesis.

Bottom line

Gastric acid is essential for solubilizing non-heme iron for absorption. Hypochlorhydria caused by H. pylori or chronic PPI use impairs this process, frequently resulting in a laboratory profile of low serum iron and elevated TIBC.