No single vitamin or dietary supplement has been clinically proven to reliably cut the risk of developing dementia by a definitive forty percent across general populations. While observational nutrition studies have occasionally explored the potential neuroprotective benefits of B vitamins—particularly targeting elevated homocysteine levels associated with cognitive decline—or vitamins D and E, randomized controlled trials have yielded mixed and frequently inconclusive results. Major medical organizations emphasize that while maintaining adequate nutritional status prevents deficiency-related cognitive impairments, vitamins cannot serve as a standalone preventative cure for complex neurodegenerative syndromes like Alzheimer's disease. Comprehensive lifestyle measures, including cardiovascular health management, regular physical exercise, balanced diets like the Mediterranean pattern, and active cognitive engagement, remain the most validated approaches for supporting long-term brain health.