Both reports were drawn from large-scale, prospective community studies of aging, one in Rotterdam, the Netherlands, and the other in Chicago, Illinois (the latter being noteworthy for having equal numbers of black and white participants). In their analysis of data from the Rotterdam study, Monique Breteler and colleagues at Erasmus Medical Center there found a protective effect in those whose diets were high in vitamins E and C. The Chicago data, reported by Martha Morris and colleagues, showed a protective effect only of vitamin E. Other dietary antioxidants examined (beta carotene in both studies, flavonoids in the Chicago study) did not correlate with AD risk.

Interestingly, neither study found a protective effect for vitamin supplements. This could mean that supplements are useless in protecting against AD because their biological activity differs from vitamins in food, but other possible explanations exist, as well. Breteler et al. point out that users of supplements tend to either have existing health problems or engage in a range of other “health-seeking” behaviors, any of which might affect the progression of AD. Numerous confounding factors argue against deriving conclusions from this kind of epidemiological data.

Echoing the authors' cautionary remarks, Daniel Foley of U.S. National Institute on Aging in Bethesda, Maryland, and Lon White of the Pacific Health Research Institute in Honolulu, Hawaii, present some of the arguments for reserving judgment until results from long-term clinical trials become available. Among their concerns about the present data are the reliability of the questionnaires on dietary habits, which ask about large numbers of foods consumed over long periods of time. There is an inherent possibility that people in preclinical stages of AD would be increasingly unable to provide accurate data. Similarly, preclinical disease might affect eating habits or the use of supplements.

“Nonetheless, the idea that vitamin E and vitamin C might have beneficial effects on the underlying AD process makes sense, and it seems unlikely that antioxidant-rich foods would negatively affect brain aging,” conclude Foley and White in an accompanying editorial.-Hakon Heimer.

References
Engelhart MJ, Geerlings MI, Ruitenberg A, van Swieten JC, Hofman A, Witteman JCM, Breteler MMB. Dietary intake of antioxidants and risk of Alzheimer disease. JAMA. 26 Jun 2002;287(24):3223-9. Abstract

Morris MC, Evans DA, Bienias JL, Tangney CC, Bennett DA, Aggarwal N, Wilson RS, Scherr PA. Dietary intake of antioxidant nutrients and the risk of incident Alzheimer disease in a biracial community. JAMA. 26 Jun 2002;287(24):3230-7. Abstract

Foley DJ, White LR. Dietary intake of antioxidants and risk of Alzheimer disease: Food for thought. JAMA. 26 Jun 2002;287(24):3261-3 Abstract