I recently blogged and cited references about this underappreciated yet most common form of vitamin B12 deficiency in the elderly. Another paper with similar conclusions has recently appeared in the American Journal of Medicine. Here are some of its key points.
1) Food-cobalamin malabsorption (FCM) is the most common form of B12 deficiency in the elderly, with classic pernicious anemia (PA) being seen in a minority.
2) The criteria for FCM are low B12 levels, normal Schilling test (using free cobalamin, not egg yolk bound cobalamin), absence of auto-antibodies and adequate dietary cobalamin intake.
3) These patients can absorb free (pill form) cobalamin but not food-borne cobalamin.
4) A spectrum of biochemical, hematologic and neurologic manifestations is seen, which may be milder than that seen in PA.
5) Oral B12 was effective. The investigators used 125mcg-1000mcg daily.
Caveat: All the patients in this study had FCM. Although oral cobalamin can also be used to treat PA, higher daily doses (1000mcg-2000mcg) are recommended. Oral vitamin B12 replacement is less well validated in patients with PA than in those with FCM.