Women who spend more time in the sun have a lower risk of breast cancer

Women who spend more time in the sun have a lower risk of breast cancer, which may be related to the promotion of vitamin D production by sunlight.

Breast cancer is the most common cancer among women. In 2020, breast cancer will replace lung cancer and become the world’s largest cancer. The latest global cancer burden data released by the WHO International Agency for Research on Cancer (IARC) shows that in 2020 There were 2.26 million new cases of breast cancer worldwide and 680,000 deaths. In China,  the incidence of breast cancer is also increasing year by year. According to WHO’s forecast, China will have 410,000 new breast cancer cases in 2020.

Vitamin D is a general term for a class of sterol derivatives with anti-rickets effects and similar structures. The most important ones are vitamin D3 and vitamin D2. Among them, vitamin D3 is produced by ultraviolet radiation from 7-dehydrocholesterol under the skin. But now, people are worried about tanning, skin cancer risk for beauty, and more and more people use computers for work, which greatly reduces the time people spend outdoors.

Vitamin D has a recognized role in maintaining bone and muscle health, but it may play a role in other areas, including helping prevent infections and cancer. Previous studies have shown that higher levels of vitamin D in the blood may be related to a lower risk of breast cancer.

Recently, researchers from the Danish Cancer Society published a research paper titled Occupational exposure to solar ultraviolet B radiation and risk of subtypes of breast cancer in Danish women in the journal Occupational & Environmental Medicine under BMJ.

The study shows that long-term outdoor work is associated with a lower risk of breast cancer in women under 50. The research team said that outdoor workers exposed to more sunlight will increase their vitamin D content and help prevent breast cancer. cancer. Since the second half of the 20th century, the incidence of breast cancer has gradually increased, and vitamin D deficiency may be one of the reasons.

In order to determine the relationship between exposure to sunlight (UV) and prevention of breast cancer, the research team surveyed 38,375 women under the age of 70 with primary breast cancer, and randomly selected women who were born in the same year without breast cancer As a control group. Through their complete work records, assess their UV exposure at work.

Most previous studies have relied on limited assessments of vitamin D levels rather than long-term observations of vitamin D levels. In this study, the research team used long-term exposure to sunlight as a substitute indicator of vitamin D levels. The human body mainly produces vitamin D between 10 am and 3 pm of the day. Compared with indoor workers, outdoor workers receive much more sunlight.

Researchers identified 38,375 women under the age of 70 from the Danish Cancer Registry who were diagnosed with primary breast cancer. Compare each of these breast cancer patients with five healthy women born in the same year. Retrieve their complete employment history from the records of the Danish pension fund, and then assess the sun exposure of each woman at work.

Taking into account potential factors such as reproductive history, there is no association between occupational sun exposure and overall breast cancer risk. However, long-term occupational sun exposure can reduce the risk of breast cancer after the age of 50.

Statistics show that among these women, occupational sun exposure for 20 years or more is associated with a 17% reduction in the probability of breast cancer diagnosis, and those women with the highest cumulative sun exposure are associated with an 11% reduction in the probability of breast cancer diagnosis. .

Not the author of the paper also pointed out that this is an observational study, and the estimation of the duration of sunlight exposure is also very rough. It does not consider sun exposure during leisure time and factors that may affect lifestyle, such as taking drugs, hormone replacement therapy, drinking, obesity and physical exercise, etc.

Despite these shortcomings, the research team said that these results are sufficient to show that there is a negative correlation between long-term occupational sun exposure and late-onset breast cancer. In other words, long-term outdoor work will be exposed to more sunlight and promote more vitamin D production, which has the effect of preventing breast cancer.

(source:internet, reference only)

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