Vitamin C intake and breast cancer mortality in a cohort of Swedish women
Using a food-frequency questionnaire we investigated whether vitamin C intake was associated with survival among 3405 women diagnosed with invasive breast cancer in the Swedish Mammography Cohort.
From 1987–2010, there were 1055 total deaths with 416 deaths from breast cancer. Women in the highest quartile of pre-diagnosis vitamin C intake had an adjusted HR (95% CI) of breast cancer death of 0.75 (0.57–0.99) compared with those in the lowest quartile (Ptrend=0.03). There was a borderline significant association between vitamin C intake and total mortality (HR=0.84; 95% CI=0.71–1.00; Ptrend=0.08). Among 717 breast cancer cases for whom post-diagnosis supplement use was available, there was no association between vitamin C supplement use (≈1000 mg) and breast cancer-specific mortality (HR=1.06; 95% CI=0.52–2.17).
Our findings suggest that dietary vitamin C intake before breast cancer diagnosis may be associated with breast cancer survival. In addition, post-diagnosis vitamin C supplementation at the level observed in our population was not associated with survival.