Across 3 studies, 2 reported beneficial effects of vitamin C on diastolic blood pressure, with effect sizes ranging from small to large. The median study duration was 40 days, suggesting effects may emerge over several weeks. The most prominent beneficial effect was observed in a meta-analysis of adults with diabetes, while evidence in young healthy adults was neutral.
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. One of the two beneficial studies reported a very large effect (-7.93 mmHg) in a specific population (heat-exposed workers), which may not generalize to other groups. The neutral study was conducted in young healthy participants, indicating that benefits may be more pronounced in populations with elevated baseline blood pressure or oxidative stress.
a clinically important reduction was observed in patients with diabetes (-2.27 mmHg)
There were no significant differences for any of the vascular outcomes between the three interventions groups.
diastolic BP (DBP) ... decreased by 7.93 mmHg