Posted by: bcconnections | August 16, 2012

A New Piece in the Marin County Breast Cancer Puzzle: Vitamin D

Marin County, California is known to have a high rate of breast cancer.  The reason for an increased incidence of breast cancer in this county has eluded scientists for years.  A recently published scientific study may provide an important clue for solving this mystery.  Investigators at the University of California, San Francisco, in collaboration with InterGenetics Inc., analyzed the DNA of 338 women in Marin County to determine whether variations in 19 pre-selected genes associated with increased breast cancer risk.  They discovered that women with an elevated breast cancer risk were almost twice as likely to harbor genetic alterations in the vitamin D receptor, compared to the population as a whole.

While this finding is interesting, it is also preliminary, and a larger study will be required to validate the result.  Furthermore, this study does not address whether variation in the vitamin D receptor correlates with abnormal vitamin D levels in elevated-risk women, nor does it address whether supplemental vitamin D can reduce breast cancer risk in these women.

A role for vitamin D in breast cancer risk has been suggested before, but current studies provide inconsistent and conflicting results.  Some observational studies show breast cancer risk decreases as vitamin D levels increase, while others show the opposite association or no association at all.

In November, 2011, The Institute of Medicine (IOM) issued a report, “Dietary reference intakes for calcium and vitamin D.”  In the report they state, “Evidence supports a role for vitamin D and calcium in bone health but not in other health conditions.”  The recommended vitamin D dietary allowance for individuals aged 1 to 70 is 600 IU/day, and for persons over 70 is 800 IU/day.  The IOM cautions that too much vitamin D may be harmful since it increases calcium levels, which, in turn, can cause calcium deposits in the kidneys, heart and lungs, as well as high levels of calcium in the blood.

>Marin County’s High Breast Cancer Rate May be Tied to Genetics

>Vitamin D Receptor Polymorphisms and Breast Cancer Risk in a High-Incidence Population:  A Pilot Study

>Vitamin D and Cancer Prevention:  Strengths and Limits of the Evidence

>Dietary Reference Intakes for Calcium and Vitamin D


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