Breast cancer could be a disease of vitamin D deficiency. Women who spend hours outdoors—and so are exposed to more sunlight, one of the main sources of the vitamin—run a far lower risk of developing the cancer.
The benefits of long sun exposure become apparent once a woman reaches the age of 50, and the risk could reduce by 17 percent for those who have spent the most time outdoors, researchers from the University of Copenhagen have discovered.
They analysed the lifestyles of more than 38,000 women under the age of 70 who had been diagnosed with breast cancer and compared them with healthy women. To assess sunlight exposure, the researchers looked for occupations that were mainly based outdoors, and especially between 10am and 3pm, when our body is more efficient at processing the vitamin.
The benefits of sunlight exposure in reducing breast cancer risk wasn’t evident in younger women, but appeared to have an effect in those aged 50 and older. Women who regularly spend time outdoors—such as from the work they were doing—for 20 years or longer had a 17 percent reduced risk of the cancer by the time they were 50.
The discovery supports earlier studies that had found an association between low vitamin D levels in the blood and breast cancer.
People generally are spending less time outdoors, partly because more work is based inside and recreationally people are spending less time in the sun because of ‘safe sun’ campaigns and fears of developing carcinoma, or skin cancer.
The researchers say their approach was a little crude and hadn’t taken into account other reasons for sunlight exposure, such as sport or recreational activities, but say the findings do suggest an inverse association between long-term exposure to sunlight and breast cancer risk in later life.
(Source: Occupational and Environmental Medicine, 2021; oemed-2020-107125)
