Context: It is currently not known whether dietary intakes of folate and vitamins B12 and B6, co-factors in the methylation of homocysteine, protect against Alzheimer's disease.
Objective: To examine the association between risk of incident Alzheimer's disease and dietary intakes of folate, vitamin B-12, and vitamin B-6.
Design: Prospective cohort study.
Setting: Geographically defined biracial Chicago community.
Participants: 1,041 residents, aged 65 years and older, initially free of Alzheimer's disease and followed a median 3.9 years for the development of incident disease.
Main outcome measure: Probable Alzheimer's disease identified through structured clinical neurological evaluation using standardized criteria.
Results: A total of 162 persons developed incident Alzheimer's disease during follow-up. In logistic regression models adjusted for age, sex, race, education, cognitive activities, APOE-epsilon4, and dietary intakes of vitamin E in food and total niacin, there was no association between risk of developing Alzheimer's disease and quintiles of folate intake or of vitamin B-12 intake. The adjusted odds ratio was 1.6 (95% confidence interval: 0.5, 5.2) for persons in the highest quintile of total folate intake (median of 752.7 microg/d) compared with persons in the lowest quintile of intake (median, 202.8 microg/d). Compared with persons in the first quintile of total vitamin B-12 intake (median, 3.1 microg/d) the odds ratio was 0.6 (95% confidence interval: 0.2, 1.6) for persons in the fifth quintile of intake (median, 20.6 microg/d). Intake of vitamin B-6 was not associated with incident Alzheimer's disease after control for dietary intakes of vitamin E and total niacin.
Conclusion: Dietary intakes of folate, vitamin B-12, or vitamin B-6 do not appear to be associated with the development of Alzheimer's disease.