The January, 2008 issue of the American Journal of Clinical Nutrition published the finding of researchers at the University of Cambridge and the MRC Centre for Nutrition and Cancer in Cambridge, England of an association of high vitamin C levels and a lower risk of stroke over a decade of follow up.
The study involved 20,649 men and women between the ages of 40 and 79 who participated in the European Prospective Investigation into Cancer (EPIC) Norfolk prospective study. The participants, who were free of stroke upon enrollment, received physical examinations during which blood samples were drawn and later analyzed for plasma vitamin C levels. Smoking status, medical history, and nutritional supplement use were ascertained via questionnaires completed by the subjects.
Over an average 9.5 years of follow-up, there were 147 fatal and 301 nonfatal strokes among the study participants. Not surprisingly, men and women whose plasma vitamin C concentrations were highest were less likely to be smokers, more likely to use any nutritional supplements, likelier to use supplements containing vitamin C, and had a lower prevalence of heart disease and diabetes than those whose levels were lowest. After adjustment for age, gender, and other factors, participants whose vitamin C levels were in the top fourth were found to have experienced a 42 percent lower risk of stroke than those whose levels were in the bottom quarter. Exclusion of subjects with heart attack or cancer, those who used vitamin C supplements and those whose strokes occurred within the first two years of follow-up, as well as adjustment for fruit and vegetable intake resulted in a similar association.
The authors remark that vitamin C may biochemically affect the risk of stroke, yet place greater emphasis on plasma vitamin C's potential as an indicator of stroke risk. "Given that about half of the risk of stroke is unexplained by conventional cardiovascular disease risk factors and that the predictive validity of traditional cardiovascular disease risk factors appears to diminish with age, risk markers that may help to identify those persons at greatest risk of stroke for targeted preventive interventions with established therapies, such as BP reduction, may be of interest," they conclude.
Related Health Concern: Stroke and Cerebrovascular Disease
Multiple studies have found that a diet high in fruits and vegetables lowers risk of cerebrovascular disease and both ischemic and hemorrhagic stroke (Gariballa SE 2000; Sauvaget C et al 2003). Two major reviews recommended that public health policy promote increased dietary intake of antioxidant vitamin C, beta-carotene, vitamin E, B vitamins (including folate), potassium, calcium, magnesium, vitamin D, fiber, and omega-3 fatty acids to reduce risk of stroke (Gariballa SE 2000; Johnsen SP 2004). These vital nutrients can also be obtained through dietary supplements in conjunction with a healthy diet.
Vitamin C, also known as ascorbic acid, is a water-soluble antioxidant that protects other compounds from oxidation by being oxidized itself. While it has been shown to lower blood pressure (Duffy SJ et al 1999), other long-term follow-up studies in human beings have found that vitamin C also reduces risk of cardiovascular and heart disease and stroke (Simon JA 1992; Enstrom JE et al 1992; Gale CR et al 1995). A small, well-designed study also found that giving antioxidant vitamins, particularly vitamin C, within 12 hours of an ischemic stroke increased antioxidant capacity, reduced inflammation, and reduced the oxidation of dangerous lipids (Ullegaddi R et al 2005). An earlier, 20-year follow-up study reported that higher vitamin C concentrations reduced incidence of both ischemic and hemorrhagic stroke (Yokoyama T et al 2000). Another study examined the benefit of vitamin C in overweight men with high blood pressure and found that low plasma levels of vitamin C were associated with increased risk of stroke (Kurl S et al 2002).
Although vitamin C provides cerebrovascular benefits when taken alone (Hirvonen T et al 2000), studies have shown that it may be more powerful when combined with other nutrients, vitamins, minerals, and antioxidants (Galley HF et al 1997; Sacks FM et al 2001; Fotherby MD et al 2000; Toivanen JL 1987; Hajjar IM et al 2001).
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