Does older age increase the risk of vitamin B12 malabsorption?

Older age is associated with a higher likelihood of vitamin B12 malabsorption, but primarily because gastric disorders and exposures become more common—not because aging inevitably eliminates absorptive capacity. The strongest distinction is between impaired release of food-bound B12 and loss of intrinsic-factor–dependent absorption.

Clinical evidence

• Atrophic gastritis affects an estimated 8–9% of adults aged ≥65 years and is associated with poorer B12 status. In one older-adult comparison, B12 deficiency occurred in 38% of those with atrophic gastritis versus 15% of controls.
• Hypochlorhydria impairs absorption of protein-bound B12: among people receiving omeprazole, protein-bound B12 absorption was 0.50%, versus 1.21% in controls; acidic drinks increased absorption in the hypochlorhydric group.
• This does not imply that all older adults malabsorb B12. Absorption of free/crystalline B12 can remain relatively preserved; diet, long-term acid suppression, metformin, and gastrointestinal disease or surgery are clinically relevant contributors.

Mechanisms

• Gastric acid and pepsin release B12 from dietary proteins. Atrophic gastritis can reduce acid secretion and pepsin activity, compromising this early step.
• Intrinsic factor then binds released B12 and permits receptor-mediated uptake in the distal ileum. Autoimmune parietal-cell destruction or intrinsic-factor–blocking antibodies can therefore markedly impair uptake of both food-bound and free B12.
• Passive diffusion remains possible, often estimated near 1% of a large oral dose, but is variable and does not restore normal physiology.

Clinical implications

• In suspected autoimmune gastritis, anti–intrinsic-factor antibody testing is useful, although a negative test does not exclude disease. NICE recognizes intrinsic-factor-related autoimmune gastritis as an indication for lifelong intramuscular B12 replacement.

Bottom line

• The claim is supported: age-related gastric pathology commonly impairs food-bound B12 handling, while intrinsic-factor deficiency produces a substantially more consequential absorption defect.