Greater vitamin C intake linked with reduced risk of breast cancer mortality

The results of a meta-analysis conducted by researchers at Sweden’s Karolinska Institutet indicate improved survival among women with breast cancer who had a higher intake of vitamin C from supplements or food sources. The findings were reported in the May 2014 issue of the European Journal of Cancer.

For their analysis, Holly R. Harris and her colleagues selected nine reports describing ten observational studies that included a total of 17,696 women diagnosed with breast cancer, among whom there were 1,558 deaths attributable to the disease and 2,791 total deaths. Studies examined the effect of supplementing with vitamin C following breast cancer diagnosis and/or the effect of vitamin C obtained in the diet.

When the studies that reported the effects of vitamin C supplements were evaluated, their use was associated with a 19% lower risk of total mortality and a 15% lower risk of dying from breast cancer in comparison with no use. Analysis of vitamin C from food sources uncovered a 27% lower risk of mortality and a 22% lower risk of breast cancer death in association with each 100 milligram per day increase. Comparison of high versus low dietary intake resulted in a 20% lower risk of dying and a 23% reduction in the risk of breast cancer mortality among women whose intake was categorized as high.

“To our knowledge this is the first meta-analysis to combine the limited number of published studies available on vitamin C supplement intake and dietary vitamin C intake and survival following breast cancer diagnosis,"the authors announce. "More studies of post-diagnosis supplement use, including vitamin C, are warranted to further our understanding of how their intake during chemotherapy or radiation therapy may influence breast cancer outcomes.”