Adults over 64 with lower vitamin C in their blood tended to have less gray matter and weaker connectivity in the default mode network, the brain hub tied to memory and attention. That is the finding from a cross-sectional analysis of 2,044 older Japanese adults published on June 10, 2026 in PLOS One.
Researchers at Hirosaki University combined 3T MRI scans with fasting blood samples and measured plasma vitamin C directly. The association held after they adjusted for age, sex, education, Mini-Mental State Examination score, diabetes, hypertension, hyperlipidemia, smoking, alcohol, and physical activity, according to the study.
The effect sizes are modest, with standardized coefficients around 0.1, similar to what large population studies see for blood pressure or fasting glucose. Because the design is observational, the finding shows association, not cause.
What the scans actually showed
Higher plasma vitamin C tracked with better preserved gray matter and white matter volume, and with stronger structural connectivity in parts of the default mode network. The most affected regions included the posterior cingulate cortex, medial prefrontal cortex, and inferior temporal gyri, all areas that lose volume in Alzheimer's disease.
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The authors did not set a specific plasma cutoff for "low" vitamin C. They analyzed levels on a continuous scale, meaning small differences across the range mapped onto small differences in brain measurements.
"Higher plasma vitamin C levels are associated with better preserved structural connectivity of the default mode network," co-author Tomohiro Shintaku said in a statement released by PLOS. He added that the results point to the potential impact of everyday dietary habits.
How much vitamin C older adults actually need
The Recommended Dietary Allowance is 90 mg per day for men and 75 mg per day for women aged 19 and up, with an added 35 mg for smokers, according to Harvard's Nutrition Source. There is no separate higher target for adults over 65. The tolerable upper intake level is 2,000 mg per day, above which gastrointestinal upset and kidney stone risk rise.
A medium orange delivers about 70 mg. One cup of chopped red bell pepper has roughly 190 mg. Strawberries, kiwi, broccoli, Brussels sprouts, tomatoes, and even a baked potato with skin all supply meaningful amounts. For most healthy older adults, two to three servings of fresh fruit and vegetables cover the daily requirement without a pill.
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Harvard's review of the evidence finds that randomized trials have not shown a benefit of vitamin C supplements for preventing cardiovascular disease or cancer, and megadosing is not supported by the data. High-dose supplements can also raise the risk of kidney stones, an issue that already exists for other popular pills older adults take daily.
What the study does not prove
Because the researchers measured plasma vitamin C only once, they cannot say whether long-term intake or a single reading drives the pattern. They also cannot rule out that the brains and vitamin C levels reflect a third factor, such as overall diet quality or unmeasured illness. The team called for repeat measurements, longer follow-up, and studies in other populations before drawing conclusions about supplementation.
For adults over 65 who eat few fruits and vegetables, the practical takeaway is narrow. Bringing intake up to the 75-to-90 mg RDA through food is well within reach of a single citrus fruit and a cup of peppers or broccoli in a day.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.