Higher Vitamin C Levels Linked to Preserved Brain Structure and Connectivity in Older Adults, Large Japanese Study Finds
核心洞察
A cross-sectional study of 2,044 older Japanese adults found that lower plasma vitamin C levels were associated with reduced gray matter volume and weaker connectivity within the brain's default mode network.
The findings, published in PLOS ONE, represent the first direct demonstration of an association between blood vitamin C levels and structural brain network connectivity.
Researchers emphasize the observational nature of the study, noting it cannot establish causation and that the observed associations were modest compared to established risk factors like hypertension.
A new study of more than 2,000 older adults in Japan has revealed that individuals with lower levels of vitamin C in their blood tend to have less gray matter and weaker connectivity within a key brain network linked to memory and attention. The findings, published in PLOS ONE by researchers led by Haruka Nagaya of Hirosaki University, add to growing evidence that nutrition may be tied to brain health in later life.
The observational study included 2,044 participants living in Hirosaki City, Japan, who were originally enrolled in a broader investigation exploring dementia and heart disease risk. The average age was 69, and 61% of participants were female.
Study Design and Methodology
The researchers analyzed magnetic resonance imaging (MRI) scans and blood plasma samples from the cohort. They measured the volume of gray and white matter throughout the brain while accounting for differences in overall brain size. The team also examined connectivity within the default mode network (DMN), a collection of interconnected brain regions that remains active during internally focused thought and is involved in functions such as memory, self-reflection, and attention. This network is often affected by conditions such as Alzheimer's disease (搜索) and depression (搜索), according to the researchers.
The vitamin C measurement approach was more accurate than studies that relied on dietary estimates, the researchers noted.
Key Findings
After adjusting for factors that can influence brain health — including age, physical activity, education level, smoking habits, and diabetes — the researchers found that participants with lower plasma vitamin C levels generally had less gray matter and weaker connectivity within the default mode network.
"Our study demonstrates that older adults with higher blood levels of vitamin C tend to have better-preserved brain structure (gray matter) and stronger connections within the default mode network (DMN), a crucial brain network involved in memory and cognitive function," said Tomohiro Shintaku, MD, PhD, assistant professor in the Department of Radiology Graduate School of Medicine at Hirosaki University.
Shintaku added: "While diets rich in vitamin C are known to lower the risk of cognitive decline, our study is the very first to demonstrate a direct association between actual blood plasma vitamin C levels and the structural connectivity of the DMN."
Biological Plausibility and Context
Vitamin C is best known for supporting immune function, but it also acts as a powerful antioxidant and plays important roles in protecting nerve cells from oxidative stress. Previous studies have suggested that diets rich in vitamin C are associated with a lower risk of cognitive impairment in older adults. However, few studies had directly examined whether vitamin C levels circulating in the blood are related to measurable differences in brain structure and communication between brain regions.
"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," Shintaku said. "It truly highlights the potential impact of our everyday dietary habits on our brain structures."
Limitations and Cautions
The researchers were careful to emphasize the study's constraints. "Because our study is observational and cross-sectional, we can only show an association, not a cause-and-effect relationship," Shintaku noted. Other limitations include relying on a single blood measurement per participant, and the potential influence of external factors such as dietary intake, body mass index, and socioeconomic variables on the outcomes.
The link was also relatively modest compared to established risk factors like high blood pressure and blood sugar, the researchers noted. Findings from other, larger studies, including UK Biobank research with more than 9,000 people, suggest that vitamin C is just one of several factors that may influence brain health.
Because the participants were almost all older Japanese adults, the findings may not be generalized to other populations. "It is best viewed as a signal that vitamin C status may be one piece of a much larger brain-health picture," the researchers indicated.
Dietary Implications
The study underscores the importance of obtaining vitamin C from the daily diet, as humans cannot synthesize it on their own. "Our findings suggest that maintaining optimal vitamin C levels through a healthy diet — rich in citrus fruits, berries, tomatoes, and green leafy vegetables — could be a simple yet powerful way to support brain health as we age," Shintaku said.
The researchers suggest future studies should track vitamin C levels over longer periods, consider a broader range of lifestyle and dietary factors, and include participants from more diverse ethnic and socioeconomic backgrounds. Additional research will be needed to clarify the biological processes behind these associations.
The study was supported by the Japan Agency for Medical Research and Development (AMED) under Grant Numbers JP16dk0207025 and JP21dk0207053. The funder KAGOME CO., LTD. provided support in the form of salaries for two authors but had no additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.