Vitamin D deficiency is a biomarker and predictor of aggressive prostate cancer; cancer that has migrated outside the prostate. A 2017 study in the Journal of Clinical Oncology finds a major link between aggressive prostate cancer and low blood levels of vitamin D.
This is an important discovery since most people are vitamin D deficient, especially in the winter. Deficiency is common because it is difficult to have normal levels unless you get regular sunlight or are supplementing. Prostate cancer risk is one more reason for testing vitamin D levels periodically, and then correcting any deficiency with high-quality supplements. Men with dark skin, and those who avoid the sun, should absolutely be tested. People with dark skin are far more likely to be vitamin D deficient.
Since vitamin D is essential to so much of the body’s biology, we all need to make sure we are not vitamin D deficient. This is why testing is important. Keep your vitamin D levels in the upper half of the normal range. The optimal level is thought to be 50 to 70 nanograms/milliliter year-round. Meanwhile, the average vitamin D level in Chicago during the winter is only 25 ng/ml. Avoiding vitamin D deficiency is part of good preventive health care. I supplement with an extra 5000 IU daily.