New research shows higher vitamin D levels reduces incidence of breast cancer Joan Lappe from Creighton University found that women taking calcium and vitamin D had an 80% reduction in non skin cancers compared with placebo. Women should keep their vitamin D levels above adequate levels-this is above 50nmol/L. I would suggest higher than that particularly if you have had a cancer-keep the level over 100nmol/L. A Belgian study also suggested that women with higher vitamin D levels who have breast cancer have smaller tumours and better outcomes than those with inadequate levels. Obviously keeping levels up is a good idea