Vitamin D is needed to help absorb calcium and phosphorus which are essential for bone health. It can also improve muscle strength and immune function. It helps to reduce inflammation. We need to test our level of vitamin D, via a blood test, to ensure that it is not deficient – especially in Australia where we are advised to cover our skin when outdoors so as to avoid skin cancer.
There is also evidence that low levels of vitamin D can be a causal factor in the development of some cancers – adequate vitamin D levels slow the growth of abnormal cells. Research has also shown that the lower the level of vitamin D, the more aggressive is the prostate cancer (https://www.harvardprostateknowledge.org/low-vitamin-d-tied-aggressive-prostate-cancer).
A 2014 study, “Vitamin D Deﬁciency Predicts Prostate Biopsy Outcomes” by Adam B. Murphy, Yaw Nyame, Iman K. Martin, et al. (Clin Cancer Res 2014;20:2289-2299), concluded that in African American men, vitamin D deficiency was associated with increased odds of prostate cancer diagnosis on biopsy. In both European American and African American men, severe deficiency was positively associated with higher Gleason grade and tumour stage.
Men with dark skin absorb less ultraviolet light from the sun than men of a lighter complexion, and so tend to make less vitamin D.
I had read about Vitamin D, skin cancer, cholesterol, and prostate cancer in a wonderful 2007 book, “Survival of the sickest” by Dr. Sharon Moalem. Our skin converts cholesterol to vitamin D when we are exposed to ultraviolet B in sunlight. Australia’s “Slip-Slop-Slap” anti-skin cancer campaign succeeded in reducing sun exposure and it seems that vitamin D deficiencies rose. He mentions a growing belief that vitamin D inhibits the growth of cancer cells in the prostate.
Blood tests have revealed my level of vitamin D to be slightly deficient before and after my diagnosis. I now aim to take 2,000 IU per day.
It seems that exposure to sunlight is important for prevention and containment of prostate cancer and is a factor in keeping the level of cholesterol down – through the action of converting cholesterol into vitamin D.
There is evidence that high-dose vitamin D can prevent progression of prostate cancer for men on active surveillance (the safety of high-doses needs to be confirmed). Researchers at Macquarie University and Cancer Council NSW are conducting a trial to evaluate the benefits and risks (Prostate News January 19, published by the Prostate Cancer Foundation of Australia).