Research from Professor Reinhold Vieth of the University of Toronto indicates that widely fluctuating levels of vitamin D—due to season-related sun exposure and sun deprivation—may increase the risk of prostate and pancreatic cancer.
At least two prostate cancer studies and two pancreatic cancer studies show that higher baseline levels of vitamin D at latitudes far from the equator increase the risk of these two malignancies. Vieth relates this increased risk to widely fluctuating levels of vitamin D in individuals who rely on summer sun exposure for their dose of vitamin D. Basically, when vitamin D levels fall abruptly, it takes several weeks or even months for the enzyme that makes activated vitamin D inside cells to adjust to the change.
Sources:
Vitamin D Council: September 2009 Newsletter: Vitamin D Studies Of Interest
