Low Vitamin D levels can cause problems in women. A research conducted by Mount Sinai Hospital Toronto measured the Vitamin D levels in the blood of 500+ women when they were having their breast cancer diagnosis. The study showed that women with no evidence of the disease were the ones with adequate levels of Vitamin D.
Hence it means that a healthy and good level of Vitamin D is important than just maintaining strong bones. It has to be noted that vitamin D does not help treat Breast cancer so if you have breast cancer it will not help having supplements. The study also show women with high levels of Vitamin D are more at risk of succumbing to the disease.
Between 400-600IU is a good amount of Vitamin D a person should get. The easiest source would be 15 minutes in the sun. Some food contain Vitamin D like fish) mackerel, tuna and salmon, Beef liver and egg yolks.