Indeed, vitamin D deficiency at the time of diagnosis is associated with a worse prognosis in melanoma.12 Patients with stage IV melanoma had a two-fold worse prognosis if they suffered from vitamin D deficiency at diagnosis. Furthermore, those who began with vitamin D deficiency and whose vitamin D levels either fell or increased by no more than 20 ng/mL had a hazard ratio of 4.68 (meaning a higher risk) compared to patients who were not deficient initially and whose vitamin D increased by more than 20 ng/mL over time.
However, a large placebo-controlled study involving over 36,282 post- menopausal women compared women who were supplemented with 400 IU of vitamin D3 and 1,000 mg of elemental calcium— every day for seven years—with controls given a placebo.13 Rates of skin melanoma and non-melanoma skin cancer were monitored over the seven-year period. There was no difference in rates of either benign or malignant cancers between the two groups. This strongly suggests that vitamin D is not the reason for the improved melanoma survival with sun exposure.
MELANIN, INFRARED LIGHT, AND SKIN CANCER
Melanin is able to transform 99.9% of absorbed sunlight into heat, and this greatly reduces the skin cancer risk. It also enhances the amount of infrared you can receive from the sun.
A fascinating 2017 study experimented with a novel idea to protect mice from skin cancer.14 It involved a new technique to treat melanoma skin cancer using a transdermal skin patch containing melanin and infrared light exposure. Since melanoma tumor cells produce high amounts of melanin, the researchers created a skin patch from ruptured melanoma cells that they applied to the skin of mice (as a source of melanin). They compared three groups of mice: the controls, mice with only the patch, and mice with the patch plus infrared light exposure. Viable melanoma cells were subsequently injected into all three groups to induce skin cancer. 100% of the control group succumbed to melanoma cancer within a two month period. Among the group with just the patch, only 13% of the mice survived. Remarkably, the mice who received both the infrared light and the patch were all still living after two months, and 87% had no tumors. One wonders what would have happened with only infrared and no patch!
SUNLIGHT, VITAMIN D SUPPLEMENTS, AND CANCER
In the following sections, I will address evidence that sunlight is protective against four distinct diseases and conditions: cancer, heart disease, hypertension, and bone fractures. In each case, studies have shown that vitamin D supplements cannot replace these benefits of sunlight.
As far back as 1980, epidemiological studies showed an inverse geographical relationship between the amount of solar radiation and mortality rates for colon cancer.15 In the forty years since then, numerous studies have shown that a high serum level of vitamin D is associated with reduced cancer risk for diverse types of cancer.
A review paper published in 2018 with 140 references revealed that those with higher serum vitamin D have an improved odds ratio protecting against developing brain, cervical, endometrial, esophageal, ovarian, thyroid, and head and neck cancers as well as gastric adenocarcinoma, hepatocellular carcinoma, and lymphoma.16 Moreover, for many types of cancer, those with higher serum vitamin D at the time of cancer diagnosis have statistically improved survival times.