A recent study found that solar radiation is associated with a decreased incidence and mortality rate of leading cancers in the United States.
Research continues to support the role of vitamin D and sun exposure in maintaining a healthy immune system. Vitamin D not only enables proper communication between immune cells, but also promotes programmed cell death (apoptosis) when a cell is no longer needed or is not functioning properly.
Since cancer occurs as a result of uncontrolled cell division, researchers believe that vitamin D is crucial for decreasing the risk of cancer through its relationship with the immune system. There have been many studies published over the years that have supported this relationship. Dr. Bill Grant, a board member of the Vitamin D Council, discussed the latest research on the relationship between vitamin D and ultraviolet B radiation (UVB) on cancer back in 2013.
Despite the abundance of research on UVB and cancer incidence and mortality, no studies to date have used the National Latitude Data Assimilation System (NLDAS), a highly accurate source for measuring solar energy, as a tool to evaluate UVB exposure over time. Therefore, researchers recently evaluated the previously reported studies on UVB and cancer using NLDAS.
The researchers gathered the NLDAS statistics for the continental United States from 1999-2011. The age-adjusted invasive cancer incidence and mortality rate was collected from the Centers for Disease Control and Prevention (CDC) during the same time period. Invasive cancers refer to cases in which cancer has spread to surrounding tissues.
Here is what the researchers found:
- Increased solar radiation energy was significantly associated with a decreased incidence of all invasive cancers (p < 0.001).
- Solar radiation was inversely associated with the incidence of 11 of the 22 leading cancers, including brain/nervous system cancer, breast cancer, colon/rectum cancer, uterine cancer, esophageal cancer, larynx cancers, non-Hodgkins lymphoma, uninary bladder cancer (p < 0.01), leukemia, (p = 0.002), ovarian cancer (p = 0.02) and prostate cancer (p = 0.03).
- The remaining cancers were not significantly associated with solar radiation, with the exception of cervical-uteri and liver cancers, which experienced a positive correlation between UVB and cancer incidence (p = 0.02 and p = 0.003, respectively).
- Increased solar radiation energy was associated with a decreased risk of mortality from the following cancers: uterine cancer (p = 0.01), esophageal cancer (p < 0.001), leukemia (p = 0.002), lung cancer (p < 0.001), non-Hodgkins lymphoma (p < 0.001), ovarian cancer (p = 0.006) and urinary bladder (p < 0.001).
- In fact, only liver cancer was associated with an increased mortality in areas with higher UVB exposure (p < 0.001).
The researchers concluded:
“The current study confirms studies relating UV radiation to the incidence and mortality of a variety of cancer types.”
Although this study adds validity to the current research supporting the role of UVB in cancer incidence and mortality, the researchers pointed out that, “the relationship between cancer and light energy is complex, and is modulated by many other environmental and genetic factors.” In other words, there may be other photoproducts aside from vitamin D that contribute to this relationship. Additionally, the cancer data utilized in the study may be subject to measurement bias, potentially skewing the results. Lastly, the study was unable to track the movement of individuals between the US states.
In order to determine if UVB may be able to aid in the prevention or treatment of cancer, future large scaled randomized controlled trials are needed.
Sturges, M. & Cannell, JJ. Solar radiation linked with incidence and mortality of several invasive cancers. The Vitamin D Council Blog & Newsletter, 2016.