In my case, I have lived for decades in sun-deprived north latitude and was never told by family doctor to take Vit D supplements, so I am sure that didn't help. There is no BC in my family history, I never took the pill, no hormone treatments, no smoking, rarely a glass of wine, vegetarian diet, reasonable exercise, not overweight...one possible additional factor, had a cyst removed from the same breast when I was a teenager long before the cancer, and much later, some years before the cancer, had a negative tumor biopsy in same breast...I wonder if those interventions had any impact.