Vitamin D, sun exposure, and decreased advanced breast cancer risk

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Vitamin D likely responsible for decreased risk of advanced breast

cancer in women with greater sun exposure

 

An article published online on October 12, 2007 the American Journal of

Epidemiology revealed the finding of researchers from the Northern

California Cancer Center, the University of Southern California, and

Wake Forest University School of Medicine that increased levels of

vitamin D in the body which are found among those with greater sunlight

exposure are associated with a reduced risk of developing advanced

breast cancer, defined as disease that has spread beyond the breast.

 

Esther John, PhD of Northern California Cancer Center and colleagues

matched 1,788 Hispanic, African-American, and non-Hispanic White women

with newly diagnosed breast cancer with 2,129 control subjects. To

calculate sun exposure, the color of underarm skin, which is not usually

directly exposed to sunlight, was classified as light, medium, or dark,

and compared with the color of the forehead, which is normally exposed

to the sun.

 

The team determined that light skinned women with the most exposure to

the sun had half of the risk of developing advanced breast cancer than

those whose exposure was low. Because the finding occurred in only one

group of women, the researchers suggest that the effect was due to

differences in vitamin D production. The effect was seen only in

advanced and not localized breast cancer, which may mean that vitamin D

slows the growth of breast cancer cells.

 

& ldquo;We believe that sunlight helps to reduce women & rsquo;s risk of

breast cancer because the body manufactures the active form of vitamin D

from exposure to sunlight, & rdquo; Dr John stated. & ldquo;It is possible

that these effects were observed only among light- skinned women because

sun exposure produces less vitamin D among women with naturally darker

pigmentation. & rdquo;

 

The authors do not recommend reducing breast cancer risk by sunbathing

because the practice increases the risk of skin cancers. Rather, they

suggest increasing the intake of the vitamin from fortified foods, fish,

and supplements. & ldquo;If future studies continue to show reductions in

breast cancer risk associated with sun exposure, increasing vitamin D

intake from diet and supplements may be the safest solution to achieve

adequate levels of vitamin D, & rdquo; stated coauthor Gary Schwartz, PhD,

of the Comprehensive Cancer Center at Wake Forest University School of

Medicine.

 

Co-researcher Sue Ingles, PhD added, & ldquo;Since many risk factors for

breast cancer are not modifiable, our finding that a modifiable factor,

vitamin D, may reduce risk is important. & rdquo;

 

Health Concern

Breast cancer

 

A wide variety of factors may influence an individual's likelihood of

developing breast cancer; these factors are referred to as risk factors.

The established risk factors for breast cancer include: female gender,

age, previous breast cancer, benign breast disease, hereditary factors

(family history of breast cancer), early age at menarche (first

menstrual period), late age at menopause, late age at first full-term

pregnancy, obesity, low physical activity, use of postmenopausal hormone

replacement therapy, use of oral contraceptives, exposure to low-dose

ionizing radiation in midlife and exposure to high-dose ionizing

radiation early in life.

Vitamin A and vitamin D3 inhibit breast cancer cell division and can

induce cancer cells to differentiate into mature, noncancerous cells.

Vitamin D3 works synergistically with tamoxifen (and melatonin) to

inhibit breast cancer cell proliferation. The vitamin D-3 receptor as a

target for breast cancer prevention was examined. Pre-clinical studies

demonstrated that vitamin D compounds could reduce breast cancer

development in animals. Furthermore, human studies indicate that both

vitamin D status and genetic variations in the vitamin D-3 receptor

(VDR) may affect breast cancer risk. Findings from cellular, molecular

and population studies suggest that the VDR is a nutritionally modulated

growth-regulatory gene that may represent a molecular target for

chemoprevention of breast cancer (Welsh et al. 2003).

 

Daily doses of vitamin A, 350,000 to 500,000 IU were given to 100

patients with metastatic breast carcinoma treated by chemotherapy. A

significant increase in the complete response was observed; however,

response rates, duration of response and projected survival were only

significantly increased in postmenopausal women with breast cancer

(Israel et al. 1985).

 

http://www.lef.org/protocols/prtcl-022.shtml

 

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