Washington, May 16 : A new research has found that lack of exposure to sunlight, specifically ultraviolet B (UVB), is clearly linked to breast cancer.
Researchers at the Moores Cancer Center at University of California, San Diego (UCSD) and the Department of Family and Preventive Medicine have analysed recently available worldwide data and shown that deficiency in exposure to sunlight, specifically ultraviolet B (UVB) is linked to breast cancer.
UVB exposure triggers photosynthesis of vitamin D3 in the body. This form of vitamin D is also available through diet and supplements.
For the study, the researchers have used the recently available data through a new tool called GLOBOCAN, developed by the World Health Organization's International Agency for Research on Cancer. GLOBOCAN is a database of cancer incidence, mortality and prevalence for 175 countries.
"This is the first study, to our knowledge, to show that higher serum levels of vitamin D are associated with reduced incidence rates of breast cancer worldwide," said Cedric F. Garland, Dr. P.H., professor of Family and Preventive Medicine in the UCSD School of Medicine, and member of the Moores UCSD Cancer Center.
By using this data, the researchers created a graph with a vertical axis for breast cancer incidence rates, and a horizontal axis for latitude. The latitudes range from -50 for the southern hemisphere, to zero for the equator, to +70 for the northern hemisphere.
Later, they plotted age-standardized incidence rates for 175 countries according to latitude. The chart that they obtained was a parabolic curve that looked like a smile.
"In general, breast cancer incidence was highest at the highest latitudes in both hemispheres. Even after controlling for known variables such as meat, vegetable and alcohol intake, cigarette consumption, weight, fertility and others, the inverse association of modeled vitamin D status with breast cancer incidence remained strong," said Garland.
The authors have also warned that this was a study of aggregates, or countries, rather than individuals. So, findings that apply to aggregates may not apply to individuals.
The study is published in the latest issue of The Breast Journal.