Among 850 Japanese adults aged 65 and older, those consuming the highest amounts of dietary fiber showed 55% lower odds of developing asymptomatic intracranial atherosclerotic stenosis compared to lowest consumers. The YAHABA Study found 15.9% of participants had significant brain artery narrowing detectable by MRI, with fiber intake emerging as a key protective factor alongside potassium consumption. This finding adds compelling evidence to fiber's cardiovascular benefits, extending beyond heart health to cerebrovascular protection. Intracranial atherosclerosis represents a critical precursor to stroke, making this dietary intervention particularly valuable for aging populations. The protective mechanism likely involves fiber's anti-inflammatory properties, blood pressure regulation, and improved lipid metabolism. However, the moderate correlation between fiber and potassium intake suggests these nutrients may work synergistically through plant-based foods. As a preprint awaiting peer review, these results require validation, and the cross-sectional design limits causal inference. The study's focus on older Japanese adults may also limit generalizability to other populations. Nevertheless, this research reinforces dietary fiber as a potentially powerful tool for cerebrovascular health preservation in later life.