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Folate and Vitamin B12 Deficiencies and Neurodegenerative Disease
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Martha Clare Morris, ScD; Denis A. Evans, MD; Julia L. Bienias, ScD;
Christine C. Tangney, PhD; Liesi E. Hebert, ScD; Paul A. Scherr,
PhD, ScD; Julie A. Schneider, MD. Dietary Folate and Vitamin B12 Intake and Cognitive Decline Among
Community-Dwelling Older Persons. Arch Neurol. 2005; 62: 641-645.
http://archneur.ama-assn.org/cgi/content/abstract/62/4/641
ABSTRACT
Background: Deficiencies in folate and vitamin B12 have been
associated with neurodegenerative disease.
Objective: To examine the association between rates of age-related
cognitive change and dietary intakes of folate and vitamin B12.
Design: Prospective study performed from 1993 to 2002.
Setting: Geographically defined biracial community in Chicago, Ill.
Participants: A total of 3718 residents, 65 years and older, who
completed 2 to 3 cognitive assessments and a food frequency
questionnaire.
Main Outcome Measure: Change in cognitive function measured at
baseline and 3-year and 6-year follow-ups, using the average z score
of 4 tests: the East Boston Tests of immediate and delayed recall,
the Mini-Mental State Examination, and the Symbol Digit Modalities
Test.
Results: High folate intake was associated with a faster rate of
cognitive decline in mixed models adjusted for multiple risk
factors. The rate of cognitive decline among persons in the top
fifth of total folate intake (median, 742 µg/d) was more than twice
that of those in the lowest fifth of intake (median, 186 µg/d), a
statistically significant difference of 0.02 standardized unit per
year (P = .002). A faster rate of cognitive decline was also
associated with high folate intake from food (P for trend = .04) and
with folate vitamin supplementation of more than 400 µg/d compared
with nonusers (beta = -.03, P<.001). High total B12 intake was
associated with slower cognitive decline only among the oldest
participants.
Conclusions: High intake of folate may be associated with cognitive
decline in older persons. These unexpected findings call for further
study of the cognitive implications of high levels of dietary folate
in older populations.
Author Affiliations: Rush Institute for Healthy Aging (Drs Morris,
Evans, Bienias, and Hebert), Departments of Internal Medicine (Drs
Morris, Evans, Bienias, and Hebert), Preventive Medicine (Dr
Morris), and Clinical Nutrition (Dr Tangney), and Rush Alzheimer's
Disease Center (Dr Schneider), Rush University Medical Center,
Chicago, Ill; and Division of Adult and Community Health, Centers
for Disease Control and Prevention, Atlanta, Ga (Dr Scherr).
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COMMENT: Folic acid and Vitamin B-12 work together so this study, which shows a worsening of brain function with higher intakes of folic acid, but a better outcome with Vitamin B-12 is challenging.
I wonder if this outcome is because folic acid tends to be taken in isolation as a supplement or an addition to foods such as bread, whereas Vitmin B-12 tends to be obtained from natural foods? If this is the reason, then it strengthens the case for eating real food instead of relying on supplements to make good an inadequate diet.
This may be bad news for vegans and other extreme vegetarians whose intakes are likely to be unbalanced with higher than safe intakes of folic acid, and inadequate amounts of B-12.
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