How antacids cause Vitamin B12 deficiency

Normally

- vitamin B12 binds to salivary R-binders first
- it needs acidic condition to separate them

- stomach secretes intrinsic factor
- intrinsic factor binds to vitamin B12, which protects vitamin B12 from being degraded by the enzymes and facilitate vitamin B12 absorption in the ileum

When you have chronic gastritis
- your gastric mucosa already atrophied
- causing decrease in intrinsic factor production and decrease in acid production

When you take antacids
- you further decrease the acidic level
- worsen the vitamin B12 absorption
- causing vitamin B12 deficiency