Duncan's note: This abstract concludes that increasing Vitamin D through sunlight exposure significantly decreases the risk of developing breast cancer. The authors state that they are not sure how much sunlight exposure, my understanding is that 15 to 20 minutes of sunlight per week is sufficient for attaining healthy levels of Vitamin D.
Breast Cancer Risk and Vitamin D from Sunlight
~ Esther M. John, Ph.D., Northern California Cancer Center, Union City, CA
Gary G. Schwartz, Ph.D., Sylvester Cancer Center, Univ. of Miami School of Medicine
Darlene M. Dreon, Dr. Ph., Children's Hospital Oakland Research Institute, Oakland, CA
Abstract presented at the "Era of Hope" Conference by
the Department of Defense Breast Cancer Research Program,
Washington, DC, USA. October 31 - November 4, 1997
Hypothesis. Vitamin D is produced when sunlight exposure photolyses 7-dehydrocholesterol in the skin to vitamin D. It can also be obtained from certain foods or dietary supplements. We tested the hypothesis that vitamin D reduces breast cancer risk.
Background. Breast cancer mortality rates are higher in the Northeastern United States than in the South and are inversely correlated with ultraviolet radiation. Regional differences in the prevalence of the known risk factors only partly explain the geographic variation in breast cancer mortality rates.
Experimental studies have demonstrated that 1,25-dihydroxyvitamin D [1,25-(OH)2D], the hormonally active form of vitamin D, inhibits proliferation and promotes differentiation of a number of cell lines, including breast cancer cells. The action of 1,25(OH)2D is mediated by intracellular vitamin D receptors which are expressed in many cell types, including breast cancer cells, and regulate the transcription of specific genes involved in cell growth and differentiation.
Few epidemiological studies to date have assessed the role of vitamin D in the etiology of breast cancer. We analyzed interview data from a large prospective cohort study conducted by the National Center for Health Statistics to assess whether sunlight exposure and dietary intake of vitamin D are associated with reduced breast cancer risk.
Study population. We based the analysis on interview data obtained from a cohort of women aged 25-74 years who participated in the first National Health and Nutrition Examination Survey (HNANES 1) from 1971 and were followed prospectively until 1987. We derived several vitamin D-related exposure measures from the interview, 24-hour dietary recall, and dermatological examination conducted at baseline and at the first follow-up interview conducted in 1982-84. Women diagnosed with breast cancer between the baseline interview and the 1987 follow-up survey were identified through self-report hospital records, and death certificates. We based the analysis on 4,881 white women, including 133 women who developed breast cancer during the first follow-up period.
Statistical analysis. We performed Cox proportional hazards regression analyses to estimate age-adjusted relative risks (RR) and 95% confidence intervals (CI), as well as relative risks adjusted for age, education, income, age at menarche, age at first birth, body mass index, family history of breast cancer, alcohol consumption, and physical activity. Age-adjusted relative risks are presented below.
Results. Breast cancer risk was significantly reduced among women who lived in the South at baseline (age-adjusted RR= 0.59, CI=0.35-0.98), compared to women who lived in the North. Compared to women from areas with low solar radiation, we also found significant reductions in risk among women who were born in regions with high solar radiation (RR=0.53, CI=0.32-0.87) or whose longest residence was in regions with high solar radiation (RR=0.58, CI=0.36-0.95). The risk reduction was similar for women who lived for at least 20 years (RR=0.54, CI=0.28-1.02) or more than half their lifetime (RR=0.57) in areas of high solar radiation. Compared to women with little sunlight exposure as assessed by the examining physician, risk was reduced among those with considerable sunlight exposure (RR=0.60, CI=0.33-1.09). Similarly, compared to women with no rare sunlight exposure, those with both frequent recreational and frequent occupational sunlight exposure had a reduced risk (RR=0.54, CI=0.28-1.02).
Considering the presence of actinic (sunlight-induced) skin damage as an indirect measure of sunlight exposure, we found no risk reduction among women with moderate or severe actinic skin damage.
With regard to dietary sources of vitamin D, the reduction in risk was highest for women with the highest intake of vitamin D, although there was no trend of decreasing risk with increasing vitamin D intake. Daily intake or 200 IU or more was associated with a relative risk of 0.63 (CI=0.38-1.03), compared to a daily intake of less than 50 IU. Regular use of multivitamins did not affect breast cancer risk.
Adjustment for potentially confounding variables with slightly changed the relative risk estimates, but resulted in a loss of statistic al significance for several exposure variables.
Discussion. This is the first analytic epidemiological study to assess the relation between sunlight exposure and breast cancer. We found consistent risk reductions for 30-40% for several measures of sunlight exposure and dietary intake of vitamin D. We could not, however, address the question of how much sunlight exposure per day might potentially reduce breast cancer risk. Because the data were obtained prospectively, the results are unlikely to be due to recall bias. They are based, however, on a relatively small number of breast cancer cases and need to be confirmed by other larger studies.
Conclusion. The findings of this cohort analysis support the hypothesis that vitamin D, a potentially modifiable lifestyle factor, reduces breast cancer risk. Future epidemiological studies that include larger numbers of breast cancer causes and use improved methods to assess sunlight exposure and dietary vitamin D intake are clearly warranted.
Note: Vitamin D3 is made with UV-B.
http://www.lighttherapycanada.biz/health_and_light.htm#Shiftworkers
http://snipurl.com/31iwg
Technorati Profile
Add to Technorati Favorites
~ Esther M. John, Ph.D., Northern California Cancer Center, Union City, CA
Gary G. Schwartz, Ph.D., Sylvester Cancer Center, Univ. of Miami School of Medicine
Darlene M. Dreon, Dr. Ph., Children's Hospital Oakland Research Institute, Oakland, CA
Abstract presented at the "Era of Hope" Conference by
the Department of Defense Breast Cancer Research Program,
Washington, DC, USA. October 31 - November 4, 1997
Hypothesis. Vitamin D is produced when sunlight exposure photolyses 7-dehydrocholesterol in the skin to vitamin D. It can also be obtained from certain foods or dietary supplements. We tested the hypothesis that vitamin D reduces breast cancer risk.
Background. Breast cancer mortality rates are higher in the Northeastern United States than in the South and are inversely correlated with ultraviolet radiation. Regional differences in the prevalence of the known risk factors only partly explain the geographic variation in breast cancer mortality rates.
Experimental studies have demonstrated that 1,25-dihydroxyvitamin D [1,25-(OH)2D], the hormonally active form of vitamin D, inhibits proliferation and promotes differentiation of a number of cell lines, including breast cancer cells. The action of 1,25(OH)2D is mediated by intracellular vitamin D receptors which are expressed in many cell types, including breast cancer cells, and regulate the transcription of specific genes involved in cell growth and differentiation.
Few epidemiological studies to date have assessed the role of vitamin D in the etiology of breast cancer. We analyzed interview data from a large prospective cohort study conducted by the National Center for Health Statistics to assess whether sunlight exposure and dietary intake of vitamin D are associated with reduced breast cancer risk.
Study population. We based the analysis on interview data obtained from a cohort of women aged 25-74 years who participated in the first National Health and Nutrition Examination Survey (HNANES 1) from 1971 and were followed prospectively until 1987. We derived several vitamin D-related exposure measures from the interview, 24-hour dietary recall, and dermatological examination conducted at baseline and at the first follow-up interview conducted in 1982-84. Women diagnosed with breast cancer between the baseline interview and the 1987 follow-up survey were identified through self-report hospital records, and death certificates. We based the analysis on 4,881 white women, including 133 women who developed breast cancer during the first follow-up period.
Statistical analysis. We performed Cox proportional hazards regression analyses to estimate age-adjusted relative risks (RR) and 95% confidence intervals (CI), as well as relative risks adjusted for age, education, income, age at menarche, age at first birth, body mass index, family history of breast cancer, alcohol consumption, and physical activity. Age-adjusted relative risks are presented below.
Results. Breast cancer risk was significantly reduced among women who lived in the South at baseline (age-adjusted RR= 0.59, CI=0.35-0.98), compared to women who lived in the North. Compared to women from areas with low solar radiation, we also found significant reductions in risk among women who were born in regions with high solar radiation (RR=0.53, CI=0.32-0.87) or whose longest residence was in regions with high solar radiation (RR=0.58, CI=0.36-0.95). The risk reduction was similar for women who lived for at least 20 years (RR=0.54, CI=0.28-1.02) or more than half their lifetime (RR=0.57) in areas of high solar radiation. Compared to women with little sunlight exposure as assessed by the examining physician, risk was reduced among those with considerable sunlight exposure (RR=0.60, CI=0.33-1.09). Similarly, compared to women with no rare sunlight exposure, those with both frequent recreational and frequent occupational sunlight exposure had a reduced risk (RR=0.54, CI=0.28-1.02).
Considering the presence of actinic (sunlight-induced) skin damage as an indirect measure of sunlight exposure, we found no risk reduction among women with moderate or severe actinic skin damage.
With regard to dietary sources of vitamin D, the reduction in risk was highest for women with the highest intake of vitamin D, although there was no trend of decreasing risk with increasing vitamin D intake. Daily intake or 200 IU or more was associated with a relative risk of 0.63 (CI=0.38-1.03), compared to a daily intake of less than 50 IU. Regular use of multivitamins did not affect breast cancer risk.
Adjustment for potentially confounding variables with slightly changed the relative risk estimates, but resulted in a loss of statistic al significance for several exposure variables.
Discussion. This is the first analytic epidemiological study to assess the relation between sunlight exposure and breast cancer. We found consistent risk reductions for 30-40% for several measures of sunlight exposure and dietary intake of vitamin D. We could not, however, address the question of how much sunlight exposure per day might potentially reduce breast cancer risk. Because the data were obtained prospectively, the results are unlikely to be due to recall bias. They are based, however, on a relatively small number of breast cancer cases and need to be confirmed by other larger studies.
Conclusion. The findings of this cohort analysis support the hypothesis that vitamin D, a potentially modifiable lifestyle factor, reduces breast cancer risk. Future epidemiological studies that include larger numbers of breast cancer causes and use improved methods to assess sunlight exposure and dietary vitamin D intake are clearly warranted.
Note: Vitamin D3 is made with UV-B.
http://www.lighttherapycanada.biz/health_and_light.htm#Shiftworkers
http://snipurl.com/31iwg
Technorati Profile
Add to Technorati Favorites
No comments:
Post a Comment