The research, led by Haruka Nagaya of Hirosaki University in Japan, was published on June 10, 2026, in the open access journal PLOS One.

Vitamin C and Brain Structure

Earlier studies have suggested that people who consume more vitamin C are less likely to experience cognitive impairment as they get older. However, relatively little research has examined whether vitamin C levels measured directly in the blood are associated with physical changes in the brain.

To investigate that question, the researchers analyzed magnetic resonance imaging (MRI) scans and blood plasma samples from 2,044 Japanese adults over the age of 64.

Using the MRI scans, they measured the volume of gray matter and white matter in each participant's brain while accounting for differences in overall brain size. They also examined connectivity within the default mode network, a group of interconnected brain regions that plays an important role in attention, autobiographical memory, and other cognitive functions.

Lower Vitamin C Linked to Smaller Gray Matter

After adjusting for factors that can also influence brain health, including age, education level, and physical activity, the researchers found a consistent pattern. Participants with lower plasma vitamin C levels tended to have reduced gray matter volume and weaker connectivity within the default mode network.

The results suggest that maintaining healthy vitamin C levels could potentially help support cognitive function and healthy brain aging. However, the researchers emphasize that this was an observational study, meaning it cannot determine whether vitamin C directly causes these differences in brain structure or function. More research will be needed to uncover the biological mechanisms behind these statistical associations.

Future studies could strengthen the evidence by measuring vitamin C levels repeatedly over time, considering additional lifestyle and dietary factors, and including participants from a wider range of ethnic and socioeconomic backgrounds.

Everyday Diet and Brain Health

Tomohiro Shintaku adds: "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."

He continued: "What I found most fascinating about this research is that we were able to detect these subtle but significant associations between a single nutritional factor and large-scale brain networks by utilizing a robust, community-based cohort of over 2,000 older adults. It truly highlights the potential impact of our everyday dietary habits on our brain structures."

Funding: The KAGOME CO., LTD. provided support in the form of salaries for authors D.K. and Y.U., but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the 'author contributions' section. Additionally, this research was supported by the Japan Agency for Medical Research and Development (AMED) under Grant Numbers JP16dk0207025 and JP21dk0207053.