In a study of 70,000 women, scientists concluded that sufficient UVB exposure was the key element in boosting vitamin D production – and that diet or nutritional supplements only play a supporting role.
These are the findings of researchers from the French National Institute for Health and Medical Research (Institut National de la Santé et de la Recherche Médicale[INSRM]) in Paris, obtained during a study published in the professional journal Cancer Epidemiol Biomarkers.
The scientists state that regular sun exposure and a vitamin D-rich diet reduce the risk of developing breast cancer by around 32 to 43 percent. They also surmise that the deciding factor in prevention is exposure to adequate UVB rays. Admittedly, food that is rich in vitamin D, such as fish, dairy products, eggs and certain types of oils or food supplements, can boost the effects of the sun, but used alone, researchers believe they have little effect on the occurrence or progression of the disease.
According to the Sunlight Research Forum, in this study, scientists observed approximately 70,000 women during a period of 10 years. In this time, 2,871 cases of breast cancer were diagnosed. According to the study, women who live in sunny regions such as Provence and who eat a vitamin D-rich diet have a far lower risk of developing breast cancer than women who have less sun exposure, who live in cloudier areas and who ingest less vitamin D through their food or food supplements.
The conclusion of the research group is: “A high dose of vitamin D via exposure to sunlight and nutrition is necessary in order to obtain a sufficient protective effect against breast cancer. However, this value is very difficult for women to achieve in northern countries as the sunlight in these regions is not strong enough to ensure a sufficient supply of vitamin D.” Furthermore, the scientists explain, following the time of menopause, it is far more difficult to achieve the protective effect from the combination of sun and a vitamin-D rich diet.
Pierre Engel, Guy Fagherazzi, Sylvie Mesrine, Marie-Christine Boutron-Ruault, Francoise Clavel-Chapelonet: “Joint Effects of Dietary Vitamin D and Sun Exposure on Breast Cancer Risk: Results from the French E3N Cohort” in Cancer Epidemiol Biomarkers Prev 2011;20:187-198.
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