Can vitamin D prevent a stroke?

Vitamin D levels in the blood have been associated with blood pressure and blood clotting, two risk factors for stroke. In studies of populations, lower vitamin D levels were associated with heart disease and stroke. However, studies in which vitamin D was given to individuals have shown no benefit, suggesting that the associations seen in studies are due to other causes. In short, vitamin D supplementation does not appear to prevent a stroke, although vitamin D deficiency may need to be treated for other reasons, such as to prevent osteoporosis, as directed by a doctor.