What is the role of vitamin D in prostate cancer risk-reduction?

Updated: Oct 11, 2019
  • Author: Mark A Moyad, MD, MPH; Chief Editor: Edward David Kim, MD, FACS  more...
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The major and most important source of vitamin D is sunlight, but this vitamin is also contained in dairy products, eggs, vitamin D–fortified cereals, and fatty fish such as salmon and tuna. Serum 25-hydroxyvitamin D assays are readily available, and many men test as vitamin-D deficient. As discussed above, however, that assay can be influenced by multiple intrinsic and extrinsic factors (eg, smoking, obesity, inflammation). Consequently, this test should not be widely advocated until further validation with so-called hard clinical endpoints has been accomplished.

Guidelines on vitamin D from the Institute of Medicine (IOM), published in 2011, set the Recommended Dietary Allowance for vitamin D at only 600 IU (800 IU in those age 71 and older), because of the concern for toxicity (eg, hypercalcemia, hypercalciuria, nephrolithiasis) and the lack of impressive data to advocate for higher amounts. [69, 70] Admittedly, the IOM recommendations have not been without controversy. [71]

Vitamin D appears to have some of the same historical embellishment issues that occurred before randomized trials of other dietary supplements for prostate cancer, when some clinicians and patients believed that "the more the better". In fact, results of studies of vitamin D for prostate cancer prevention have not been consistently impressive, and several studies have found no impact or potential harm at higher blood levels. [72, 73, 74]

Vitamin D is important for bone health, but recommendations for higher intakes to support prostate health have not been supported by strong clinical trial evidence. Vitamin D tends to mimic the function of a hormone, which is why caution should be followed because the potential for a U-shaped risk curve (similar to that seen with other hormones, and even alcohol) does exist for men's health. 

It may be tempting to endorse the general findings of an increased risk of prostate cancer mortality with lower vitamin D blood status, but again the issues with the assay and the history of prostate cancer supplements being discredited argue for a “first do no harm” approach until larger trials are published that give further insight. Clinical trials such as  the VITamin D and OmegA-3 TriaL (VITAL) [75] should be published soon and they will provide further insight into the benefits and limitations of vitamin D supplementation to prevent cancer.

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