High plasma vitamin C tied to better brain structure in older adults

Clinical takeaway: The findings add plasma vitamin C status to the markers linked with brain structure in aging, but the study was cross-sectional and tested no intervention, so it doesn't support supplementation.

Most evidence on vitamin C and the aging brain rests on dietary intake, not measured blood levels. This study examined whether in older adults plasma vitamin C is independently associated with brain volume and connectivity in the default mode network (DMN) that's involved in memory and attention.

After adjusting for age, sex, education, cognitive score, vascular conditions, and lifestyle factors, higher plasma vitamin C was independently associated with greater gray matter volume and greater white matter volume, each scaled to head size. The associations were modest but statistically robust.

Vitamin C levels also tracked with connectivity in all three DMN components the researchers identified. Two ran in the expected direction, with higher vitamin C tied to stronger connectivity.

The third ran the opposite way: more vitamin C, less connectivity. That sounds like a contradiction but this network is one that builds up with age as a sign of decline, not health. So lower connectivity here lines up with the other two findings rather than against them. A separate, more fine-grained analysis confirmed the same regions, with the strongest signal in the posterior cingulate cortex, a core DMN hub.

Plasma vitamin C isn't directly correlated with cognitive test scores. The link to cognition appears only indirectly, through the DMN components that themselves track with test performance. The effect sizes throughout are small, which the authors argue is on par with established risk factors such as blood pressure and blood glucose.

The cross-sectional study drew on 2,044 community-dwelling Japanese adults over age 64 from the Iki-Iki Health Promotion Project. All underwent 3T MRI, with vitamin C measured from a single fasting blood draw. Part of the work was funded by Kagome, a health-food company whose employees co-authored the paper and measured the vitamin C levels.

The result extends literature built mostly on dietary recall to a measured biomarker. This is the first study to tie plasma vitamin C to brain network connectivity. Whether maintaining vitamin C status changes brain aging trajectories will require longitudinal or interventional work.

"Our study demonstrates that higher plasma vitamin C levels are associated with better preserved structural connectivity of the default mode network (DMN), a key brain network involved in cognitive function. This finding generates the exciting hypothesis that a diet rich in vitamin C might play a supportive role in maintaining brain health and mitigating age-related cognitive decline in older adults," said Tomohiro Shintaku of the Department of Radiology, Hirosaki University Graduate School of Medicine.

Source: Nagaya H. PLoS One. 2026 Jun 10. Plasma vitamin C levels are associated with brain structural networks on MRI: A large cohort study