Metabolic evidence of vitamin B-12 deficiency, including high homocysteine and methylmalonic acid and low holotranscobalamin, is more pronounced in older adults with elevated plasma folate.
BACKGROUND
An analysis of data from the National Health and Nutrition Examination Survey indicated that in older adults exposed to folic acid fortification, the combination of low serum vitamin B-12 and elevated folate is associated with higher concentrations of homocysteine and methylmalonic acid and higher odds ratios for cognitive impairment and anemia than the combination of low vitamin B-12 and nonelevated folate. These findings await confirmation in other populations.


OBJECTIVE
The purpose was to compare metabolic indicators of vitamin B-12 status, cognitive function, and depressive symptoms among elderly Latinos with elevated and nonelevated plasma folate.


METHODS
Cross-sectional data were analyzed for 1535 subjects (age: >or=60 y) from the Sacramento Area Latino Study on Aging. Subjects were divided into 4 groups on the basis of plasma vitamin B-12 (< or >or=148 pmol/L) and folate (<or= or >45.3 nmol/L). Homocysteine, methylmalonic acid, holotranscobalamin, ratio of holotranscobalamin to vitamin B-12, Modified Mini-Mental State Examination, delayed recall, and depressive symptom scores were compared between the groups.


RESULTS
Individuals with low vitamin B-12 and elevated folate (n = 22) had the highest concentrations of homocysteine and methylmalonic acid and the lowest concentration of holotranscobalamin and ratio of holotranscobalamin to vitamin B-12 when compared with all other groups (P <or= 0.003). No differences in Modified Mini-Mental State Examination, delayed recall, and depressive symptom scores were observed between the low vitamin B-12 and elevated-folate group compared with other groups.


CONCLUSIONS
Low vitamin B-12 is associated with more pronounced metabolic evidence of vitamin B-12 deficiency when folate is elevated than when folate is not elevated. These data should be considered when assessing the potential costs, risks, and benefits of folic acid and vitamin B-12 fortification programs.
Miller
Joshua W
JW
School of Medicine, Department of Medical Pathology and Laboratory Medicine, University of California, Davis, CA, USA.
Garrod
Marjorie G
MG
Allen
Lindsay H
LH
Haan
Mary N
MN
Green
Ralph
R
D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005260:Female; D005492:Folic Acid / Q000097:blood*; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D008297:Male; D008764:Methylmalonic Acid / Q000097:blood*; D008875:Middle Aged; D014155:Transcobalamins / Q000032:analysis*; D014806:Vitamin B 12 Deficiency / Q000097:blood*
D014155:Transcobalamins; D006710:Homocysteine; D008764:Methylmalonic Acid; D005492:Folic Acid