Dr. Vannier, and his colleagues, studied 130 people. Half of those people had not had a stroke while the other half had suffered one. Out of all 130 people, 45 percent had vitamin C levels that were classified as being very low. Another 45 percent of the study participants had levels of vitamin C that were normal. Of those 65 people in the study that had never had a stroke, all of them had normal levels of vitamin C.