Most of the acid-blocker studies found no difference at all
Across 25 observational studies, people on proton pump inhibitors had 42 percent higher odds of B12 deficiency, but most of the studies found no difference in blood B12.
What the study found
Acid blockers' 42 percent B12 signal rests on studies that disagree
Across 25 observational studies, people on proton pump inhibitors had 42 percent higher odds of B12 deficiency. The reviewers would not call it clear: the studies disagreed, and most found no difference in blood B12. A separate cohort saw it only above 30 milligrams of the drug a day.
The caveat · Users may already differ in B12 risk
Every included study was observational, and people on long-term acid blockers differ from those who are not in ways that also affect B12. Heterogeneity was high, with just over half the variation between studies not attributable to chance. The review was not registered in advance.
What we don't know
Every included study was observational, and people on long-term acid blockers differ from those who are not in ways that also affect B12. Heterogeneity was high, with just over half the variation between studies not attributable to chance. The review was not registered in advance.