Prostate Cancer, Shift Work and Vitamin D
One out of six American men will develop prostate cancer and more than a third of them will experience a recurrence after undergoing treatment, putting them at high risk to die of the disease.
A study from Japan in this month’s issue of the American Journal of Epidemiology, reports prospective research that examined the association between shift work and the risk of prostate cancer incidence among 14,052 working men. Compared with day workers, people who worked rotating shifts were significantly at risk for prostate cancer whereas fixed-night work was associated with a small and non-significant increase in risk. This report is the first to reveal a significant relation between rotating-shift work and prostate cancer. Previous research has found that shift work may be linked to an increased risk of breast and colon cancer.
It’s important not to jump off the deep end: we are long way from saying that sleep disturbance is linked to prostate cancer. But it is another piece of evidence suggesting a link between environmental factors and genes, since there are a number of genes that may increase a man’s risk for prostate cancer.
However, there have now been several reports that disturbances in normal body rhythms might be linked to some cancers and this report adds to that evidence. It has never been shown that the actual sleep disturbance itself is responsible for the slight increase in risk seen in these studies. It could also be that people with abnormal sleep patterns are more likely to be doing something else, for instance smoking or eating junk food that would interfere with sleep and increase people’s cancer risk.
But here’s something to think about: shift workers have been found to have reduced secretion of the sleep-inducing hormone melatonin. Melatonin has also been shown in some studies to have some potential anti-cancer effects. The studies are controversial and certainly not conclusive, despite what one or two melatonin manufacturers may say. But something that is true is that reduced secretion of melatonin has been linked to increased production of sex hormones, which play a role in regulating prostate tissues.
Under normal circumstances, secretion of the hormone is low during daytime, increases soon after the onset of darkness, peaks in the middle of the night, and gradually falls until morning. In shift workers the melatonin cycle becomes disrupted.
There has been some recent evidence that maintaining adequate levels of vitamin D may reduce a man’s risk of prostate cancer.
Another study, this time on pancreatic cancer and led by Northwestern University in Illinois has indicated that taking the US Recommended Daily Allowance (RDA) of vitamin D (400 IU/day) reduces the risk of pancreatic cancer by 43%. It is published in this month’s issue of Cancer Epidemiology Biomarkers & Prevention. This does not mean that we should start taking vitamin D supplements to reduce our cancer risk. But it ties in with research indicating that some exposure to sunlight might actually reduce the risk of some cancers. But all things in moderation: malignant melanoma and basal cell carcinoma of the skin have been increasing with increased exposure to sunlight.
Dr. Richard G. Petty, MD is a world-renowned authority on the brain, and his revolutionary work on human energy systems has been acclaimed around the globe.
He is also an accredited specialist in internal and metabolic medicine, endocrinology, psychiatry, acupuncture and homeopathy. He has been an innovator and leader of the human potential movement for over thirty years and is also an active researcher, teacher, writer, professional speaker and broadcaster. He is the author of five books, including the groundbreaking and best selling CD series Healing, Meaning and Purpose. He has taught in over 45 countries and 48 states in the last ten years, but spends as much time as possible on his horse farm in Georgia.
