What is the accuracy of nutrient testing for 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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Answer

The reliability of nutrient testing is also an issue. Countless nutrient or antioxidant tests are offered today to consumers who are concerned about cancer, yet the validity of many of these tests—especially as they relate to cancer and other “hard endpoints”—is unknown. Unanswered questions include the following:

  • Does the measured level in serum reflect the tissue concentration? 
  • What is the best form of the nutrient to test? 
  • Does increasing a specific nutrient because of a lower test result produce any potentially tangible benefit? 
  • How are the assay results impacted by intrinsic and/or extrinsic factors?  Do some dietary supplements in higher amounts interfere with other non-nutrient assays? 

Those and other critical questions should be answered before consumers spend their money on these tests. A few examples can help illustrate the complexity of nutrient testing, which has yet to be fully appreciated. 

For example, use of dietary supplements containing large amounts of biotin (marketed as promoting healthy hair, skin, and nails) may interfere with a variety of laboratory tests that are biotin based. High biotin intake may result in artifactually low results on PSA assays, as well as other cancer marker tests (eg, CA125, CA15-3, CEA, CA19). (False increases in thyroid function test results and vitamin B12 assays have also been reported. [44] )

Given the plethora of tests that may be impacted, patients should be advised to stop taking an individual biotin supplement at least 3 days (and perhaps ideally 1 week) before blood testing. Multivitamins that include biotin are usually not a cause for concern.

Systemic inflammation may result in low values on tests for nutrients such as zinc; selenium; and vitamins B6, C, A, and D. [45] This effect may skew interpretation of research findings because it can suggest that a nutrient deficiency increases the risk for a particular disease when in fact the disease itself is decreasing the measured nutrient level.

Vitamin D blood measurements, in particular, may be reduced not only by inflammation but by obesity, smoking, depression, cancer, and lack of physical activity. [43, 45, 46, 47] This could partly explain the lack of an effect of supplementation in some major clinical trials; that is, the inflammatory state may be creating the appearance of a vitamin D insufficiency or deficiency in individuals with adequate vitamin D intake.


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