The factors suggested to explain the disparity in mortality rates included difference in stage at diagnosis, obesity, comorbidities, tumor characteristics, as well as access, adherence, and response to treatments.
However, a study in California found that body mass index did not affect survival rates for black American women [Kwan, 2014].
No mention of the role of vitamin D in reducing risk of breast cancer and increasing survival after diagnosis was made in the American Cancer Society paper.
Case-control studies consistently find a strong protective effect of higher 25-hydroxyvitamin D concentrations at time of breast cancer diagnosis [Grant, 2015]. Two clinical trials found that vitamin D plus calcium reduced the risk of cancer including breast cancer [Lappe, 2007], [Bolland, 2011].
Also, women who live in the sunny states have much lower breast cancer mortality rates than those who live in the cloudy states in the north [John, 2007]. Solar ultraviolet-B exposure is the primary source of vitamin D for most people.
A review of differences in cancer survival rates found that after consideration of stage at diagnosis, socioeconomic status, and treatment, black Americans had about 25% increased mortality rates for most types of cancer [Grant, 2012]. The difference was consistent with the fact that black Americans have 25-hydroxyvitamin D concentrations about 40% lower than white Americans since their dark skin reduces the production rate of vitamin D in the sun.
A paper from the Roswell Park Cancer Center concluded "The relationship of vitamin D with breast cancer risk may be subtype-specific, with emerging evidence of stronger effects of vitamin D for more aggressive breast cancer, particularly in women of African ancestry." [Yao, 2013].
Further evidence that vitamin D concentration affects cancer survival rates comes from a nine-year study in Norway. The hazard ratio for the nine-year all-cause survival after diagnosis of breast cancer was much lower (63% lower) for women with higher 25-hydroxyvitamin D concentrations [Tretli, 2012].
Based on results in the peer-reviewed scientific literature [Baggerly, 2015], cancer incidence and mortality rates could be greatly reduced if everyone had 25-hydroxyvitamin D concentrations above 40 ng/mL.
An all-source vitamin D3 input of 4000 IU/d ensures that 50% of the population achieves 25-hyderoxyvitamin D concentrations above 40 ng/mL (8000 IU/d is needed for 90% of the population). [Garland, 2011].
The benefits of sunlight and vitamin D for public health were discussed at a seminar held by GrassRootsHealth.net in December 2014 [Baggerly, 2015].
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