A new UK prospective study has reported that intake of vitamin C, whether from food or supplements, does not appear to influence the risk of breast cancer. Vitamin C intake has been reported to be associated with reduced breast cancer risk in case-control studies, but not in meta-analyses of data from previously published studies that used food questionnaires. No study to date has evaluated this relationship prospectively using food diaries. Food diaries may more accurately measure vitamin C intake than questionnaires requiring study participants to recall their diets. The study included 851 breast cancer cases and 2,727 matched cancer-free controls. Dietary vitamin C intake was estimated using four- to seven-day food diaries pooled from five prospective studies in the UK Dietary Cohort Consortium. The analysis adjusting for other breast cancer risk factors to examine breast cancer risk in relation to dietary vitamin C intake. In addition, total vitamin C intake from supplements as well as diet was analyzed in the three largest studies.

No evidence was found of an association between vitamin C consumed in food and risk of breast cancer. Nor was an association found for total vitamin C intake, which included both supplemental and dietary vitamin C. Furthermore, no association was found when only postmenopausal women were considered. The authors conclude that this pooled analysis of individual UK women found no evidence of associations between breast cancer incidence and dietary or total vitamin C intake derived from detailed diary recordings.

Please see our article on vitamin C and breast cancer for information on how vitamin C influences prognosis.