"In separate analyses limited to non-demented subjects," they said, "use of either Vitamin E or C supplements alone ... was associated significantly with better cognitive test performance ... " The study, part of the ongoing Honolulu-Asia Aging Study being conducted at the University of Hawaii and other locations, suggested that "long-term use is required to improve cognitive function in late life."

Citing previous studies that suggested a combination of Vitamin E and C might provide more antioxidant effect that either alone, the researchers said that in their current study "there was a strong interaction between Vitamin E and C in promoting cognitive performance. It has been suggested, they reported, that a higher level of Vitamin C can increase Vitamin E levels.