A longitudinal study published in Neurology (March 2000;54:1265–1272) followed 3,385 Japanese American men between the ages of 71 and 93 for up to nine years to examine the relationship between antioxidant vitamin use and cognitive outcomes.

Over the course of the study:

  • 47 men were diagnosed with Alzheimer’s disease

  • 35 were diagnosed with vascular dementia

  • 50 were diagnosed with other forms of dementia

  • 254 showed low cognitive test scores without a formal dementia diagnosis

  • 2,999 showed no cognitive impairment

Men who reported regular use of both vitamin E and vitamin C supplements (defined as at least once per week) in 1988 were 88% less likely to develop vascular dementia four years later compared to non-users. They were also 69% less likely to develop non-Alzheimer’s, non-vascular, or mixed forms of dementia. No significant reduction in Alzheimer’s disease incidence was observed in supplement users.

Cognitive performance was also assessed in men who did not develop dementia. Those who reported taking both vitamins in 1988 had about a 20% greater likelihood of better cognitive performance during follow-up testing between 1991 and 1993. Notably, men who reported supplement use in both 1982 and 1988 had a 75% greater likelihood of better cognitive performance, suggesting that longer-term use was associated with more favorable cognitive outcomes.

The authors proposed that antioxidant vitamins may help protect brain tissue from oxidative damage. Oxidative stress—driven by factors such as inflammation, toxins, and metabolic activity—can damage neurons and supporting structures. Antioxidants help neutralize free radicals, potentially reducing cumulative damage over time.

The findings support the broader hypothesis that oxidative stress contributes to age-related cognitive decline, particularly in vascular forms of dementia, and that long-term antioxidant consumption may be linked with preserved cognitive function in later life.

Of course, brain health is not just about antioxidant protection. Other nutrients, like B vitamins, are important.