Summary: Researchers report a strong structural and functional link between systemic micronutrient status and age-related brain preservation. The study analyzed high-resolution magnetic resonance imaging (MRI) scans together with blood plasma vitamin C measurements from 2,044 older Japanese adults, revealing that lower plasma vitamin C in people over 64 associates with reduced cerebral gray matter volume and weakened connectivity within the brain’s Default Mode Network (DMN).
Using objective, laboratory-based plasma measurements instead of self-reported diet records, the team identified clear relationships between a circulating antioxidant and large-scale brain measures that underlie memory, self-reflection, and sustained attention.
Key Facts
- Objective biomarker over dietary recall: The study measured plasma vitamin C directly, avoiding the inaccuracy of food diaries and providing precise systemic exposure data.
- Large community cohort: The analysis included 2,044 community-dwelling Japanese adults aged 65 and older, supplying robust statistical power for MRI-based findings.
- Gray matter volume reduction: After adjusting for individual intracranial volume, lower plasma vitamin C was significantly associated with decreased gray matter volume, the tissue that contains neuronal cell bodies and synapses.
- DMN functional decline: Lower vitamin C levels correlated with diminished connectivity within the Default Mode Network (DMN), a distributed brain system that supports autobiographical memory, internal thought, and background attention processes.
- Extensive confounder control: Analyses adjusted for age, sex, cognition screening score, vascular risk factors, education, smoking, alcohol use, and physical activity to isolate the vitamin C association.
- Biological rationale: While the study is observational and does not prove causality, the authors note that vitamin C’s antioxidant properties make it a plausible protector against oxidative stress and cumulative synaptic damage with aging.
- Next steps: The investigators recommend longitudinal studies with repeated plasma measures across diverse populations and interventional trials to test whether raising vitamin C levels can slow or prevent brain tissue loss.
Source: PLOS
Haruka Nagaya of Hirosaki University and colleagues present these results in PLOS One (published June 10, 2026). The research directly links circulating vitamin C levels with structural and functional MRI markers in older adults, adding biological detail to prior dietary studies that suggested a protective role for vitamin C against cognitive decline.
In this cross-sectional analysis the researchers quantified total intracranial volume, gray matter volume (GMV), and white matter volume (WMV) from 3T MRI scans. They adjusted brain-volume measures for head size (GMV/ICV and WMV/ICV ratios) and applied independent component analysis to derive DMN connectivity metrics. Multiple regression models then tested associations between plasma vitamin C and MRI measures while controlling for demographic, clinical, and lifestyle covariates.
The principal finding was that lower plasma vitamin C was independently associated with both a smaller GMV/ICV ratio and reduced DMN connectivity (both associations highly statistically significant). These results held after accounting for cognitive screening, vascular conditions, education, and activity behaviors, indicating that the vitamin C signal is not simply a proxy for those other factors.
Although observational, the study suggests a biologically plausible link: vitamin C is an essential antioxidant that circulates in plasma and supports neuronal health by neutralizing free radicals and participating in collagen formation and neurotransmitter synthesis. If those protective mechanisms operate over decades, suboptimal plasma vitamin C could plausibly contribute to accelerated gray matter loss and weakened network function.
The authors emphasize limitations: cross-sectional design prevents causal claims, a single plasma measurement captures only one timepoint, and the cohort is ethnically homogeneous. They recommend prospective cohorts, repeated plasma sampling, and randomized trials to test whether improving vitamin C status preserves brain structure and function.
Tomohiro Shintaku commented that higher plasma vitamin C was associated with better-preserved DMN structural connectivity, raising a testable hypothesis that diets or interventions that maintain adequate vitamin C may help support cognitive aging. The research team highlights the value of combining neuroimaging and precise blood biomarkers to detect subtle but meaningful links between nutrition and brain health.
Funding: The study received support from KAGOME CO., LTD. (which provided salaries for some authors but had no role in study design or manuscript decisions) and grants from the Japan Agency for Medical Research and Development (AMED) under Grant Numbers JP16dk0207025 and JP21dk0207053. The roles of individual authors are described in the paper’s author contributions section.
Key Questions Answered:
A: No. The study demonstrates a robust statistical association but cannot establish cause and effect. Clinical trials and longitudinal studies are needed to determine whether supplementation can actively protect brain tissue.
A: The DMN is a network of brain regions active during rest and internal thought. It supports autobiographical memory, self-referential processing, and background attention. Reduced DMN connectivity is linked to cognitive decline in aging and neurodegenerative disorders.
A: The brain is vulnerable to oxidative damage over time. Vitamin C is a potent antioxidant that reaches the brain via circulation; adequate plasma levels may help neutralize damaging free radicals and support cellular processes that preserve neurons and synapses.
Editorial Notes:
- This article has been edited and reviewed by the editorial team.
- The original journal paper was reviewed in full for accuracy.
- Additional context was added by editorial staff to clarify methods and implications.
About this neuroscience research news
Author: Hanna Abdallah
Source: PLOS
Contact: Hanna Abdallah – PLOS
Image credit: Neuroscience News
Original Research: Open access. “Plasma vitamin C levels are associated with brain structural networks on MRI: A large cohort study” by Haruka Nagaya et al., PLOS ONE. DOI: 10.1371/journal.pone.0348504
Abstract
Plasma vitamin C levels are associated with brain structural networks on MRI: A large cohort study
Background
Neurodegenerative processes profoundly affect brain health in older adults. Although dietary vitamin C has been linked to lower cognitive impairment risk, it is unclear whether plasma vitamin C independently correlates with brain structure and network connectivity. This study aimed to determine whether plasma vitamin C levels associate with gray matter volume and Default Mode Network connectivity in older adults.
Methods
Participants underwent 3T MRI scanning. Total intracranial volume, gray matter volume, and white matter volume were estimated using CAT12 in SPM12. DMN connectivity was evaluated by independent component analysis and measured via loading coefficients that capture shared variance across voxels. Multiple regression assessed relationships among brain-volume ratios, DMN connectivity, and plasma vitamin C while adjusting for confounders (age, sex, Mini-Mental State Examination score, diabetes, hypertension, hyperlipidemia, education) and lifestyle factors (smoking, alcohol use, physical activity). GMV/ICV and WMV/ICV ratios were calculated to control for head size differences.
Results
The cross-sectional analysis included 2,044 participants (median age 69; 61.1% female). Lower plasma vitamin C was significantly and independently associated with lower GMV/ICV ratio (p < 0.001) and reduced DMN connectivity (p < 0.001).
Conclusions
These findings indicate that plasma vitamin C levels are positively associated with gray matter structural integrity and DMN connectivity in older adults. The results support the hypothesis that vitamin C may contribute to brain health, while highlighting the need for prospective and interventional studies to establish causality.