Could it be possible that vitamin C helps prevent stroke? Antioxidants have long been regarded as positive contributors to health. Vitamins C & E for example are often recommended for reducing the incidence of many conditions exacerbated by free radicals and oxidative stress. One condition is not so well researched as it could be – stroke. Uncovering the associations between different vitamins with acclaimed antioxidant benefits however and reducing the risk of stroke remain to be explored more fully. Up to now there has been inconsistency in many of these findings relating the role of vitamins and

Antioxidants are chemicals which quench singlet molecular oxygen and other free radicals. I’m sure we are all familiar with vitamin C which is the classic antioxidant vitamin and one too which is claimed to reverse endothelial vasomotor dysfunction in blood circulation (Levine et al., 1996). Likewise, vitamin E which is 90 per cent alpha-tocopherol protects against damage to cellular membranes by protecting the lipids from oxidation (Burlakova et al., 1998).

There is considerable interest in the association between various aspects of cardiovascular disease and oxidative stress and whether reduction of the latter can reduce the incidence of these heart conditions (Asplund, 2002).

One long term study has been assessing the incidence of total stroke and ischemic stroke and the association with consumption of the main antioxidant vitamins. The Japan Public Health Center-based Prospective Study has been looking at over 82,000 Japanese men and women who are aged between 45 and 74 years. Between the years 1995 and 1997, dietary assessments were conducted using food frequency questionnaires. An extensive follow up was conducted to the end of December 2009. In that time there were 3541 incidents of total stroke and 2138 incidents of ischemic stroke (Uesugi et al., 2017).

The main finding from the study was that dietary intakes of various antioxidants such as α-carotene, β-carotene, α-tocopherol and vitamin C were not inversely associated with the incidence of total or ischemic stroke even when the various cardiovascular risk factors and selected lifestyle variables were adjusted for. It meant that the association between antioxidant vitamins and reducing the risk of stroke did not exist for this data set.

However, the data was further examined by looking at whether each subject smoked or not. In this case dietary vitamin C was associated with a reduction in both types of stroke but just among the non-smokers. The data could not be statistically significant for smokers considering the habit is more likely to increase oxidative stress. No data was presented on any association with drinking alcohol.

The other elements which the authors suggest need to be taken into account is the presence of fibre and potassium which commonly ingested with foods which have high levels of vitamin C. The evidence so far presented suggests there is no association either between these two components of food and reduced levels of stroke.

The authors take comfort in the fact that a very large population number were involved which makes many of the results statistically relevant with a high response rate. the food questionnaire was validated and there was a an 88 per cent follow-up rate. Whilst Vitamin C does not appear to protect all people from stroke, it would seem that the evidence does suggest that Vitamin C helps prevent stroke, but only in those who don’t smoke.

Vitamin C and vitamin E are also covered in other articles on their general health benefits.

References

Asplund, K. (2002) Antioxidant vitamins in the prevention of cardiovascular disease: a systematic review. J. Intern. Med. 251 pp. 372-392

Burlakova, E.B., Krashakov, S.A., Khrapova, N.G. (1998) The role of tocopherols in biomembrane lipid peroxidation. Membr. Cell Biol. 12 pp. 173-211

Levine, G.N., Frei, B., Koulouris, S.N., Gerhard, M.D., Keaney, J.F. Jr., Vita, J.A. (1996) Ascorbic acid reverses endothelial vasomotor dysfunction in patients with coronary artery disease. Circulation 93: pp. 1107-1113

Uesugi, S., Ishihara, J., Iso, H., Sawada, N., Takachi, R., Inoue, M., Tsugane, S. (2017) Dietary intake of antioxidant vitamins and risk of stroke: the Japan Public Health Center-based Prospective Study. Eur. J. Clin. Nutr. 71(10) pp. 1179-1185 PMID: 28699629 DOI: 10.1038/ejcn.2017.71