Subclinical cobalamin [B-12] deficiency
– Source: Current Opinion in Gastroenterology, Mar 2012
By Ralph Carmel
[Note: cobalamin is vitamin B-12. “Normal” findings on serum B12 tests actually leave a large gray area between definitely deficient (clinical deficiency) and definitely sufficient. Cases of deficiencies within that gray area appear often associated with cognitive decline.]
Purpose of review: This review focuses on recent developments and controversies in the diagnosis, consequences, and management of subclinical cobalamin deficiency (SCCD), which affects many elderly persons.
Recent findings: Diagnosis of subclinical cobalamin deficiency depends exclusively on biochemical tests whose individual limitations suggest that combinations of tests are needed, especially in epidemiologic research.
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The causes of subclinical cobalamin deficiency are unknown in more than 60% of cases, which limits prognostic predictions and identification of health consequences.
After years of varying, often inconclusive associations, new clinical trials suggest that homocysteine [a risk marker for cardiovascular disease, Alzheimer’s & Parkinson’s] reduction by high doses of folic acid [B-9]), cobalamin [B-12], and pyridoxine [B-6] may reduce progression of structural brain changes and cognitive impairment, especially in predisposed individuals.
• The causative or contributory roles, if any, of subclinical cobalamin deficiency itself in cognitive dysfunction require direct study.
• If the findings are confirmed, high-dose supplementation with three vitamins will probably be more effective than fortification of the diet.
Summary: The story of subclinical cobalamin deficiency which is severalfold times more common in the elderly than clinical cobalamin deficiency, but also differs from it in arising only infrequently from severe malabsorption and thus being less likely to progress, continues to evolve.
Preventive benefits need to be confirmed and expanded, and will require fuller understanding of subclinical cobalamin deficiency pathophysiology, natural history, and health consequences.
Source: Current Opinion in Gastroenterology, Mar 2012; 28(2) pp 151–158. Carmel R. Department of Medicine, New York Methodist Hospital, Brooklyn and Weill Cornell Medical College, New York, New York, USA.