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Why do some nutritional supplements seem to delay prostate cancer progression?

Posted Jan 04 2011 12:00am

It is widely recognized that some nutritional supplements and other dietary products seem to to have some effect on risk of prostate cancer progression. The problem is that we really don’t know why or how.

In an attempt to see if they could gain greater understanding of the way two standardized nutritional supplements might be having an effect, a research team at the University of California San Francisco (UCSF) set out to test the biological effects of lycopene and fish oil supplements compared to a placebo in men already on active surveillance.

Their idea was that lycopene or fish oil supplements might have measurable effects on the expression of two different genes that control the production of enzymes like insulin-like growth factor-1 (IGF-1) and cyclooxygenase 2 (COX-2), both of which are known to be important in the growth of prostate cancer cells.

To test this idea, Chan et al. set up a brief, randomized, double-blind clinical trial among 69 men with relatively low-risk prostate cancer, all of whom were already participating in the UCSF active surveillance cohort. For a period of 3 months, the men were given a placebo (a sugar pill) or lycopene (at a dose of 30 mg/day) or fish oil (at a dose of 3 mg/day). A test called a qRT-PCR test was then used to measure the expression of the genes for IGF-1 and COX-2.

Here is what they found:

  • 22/69 men were treated with lycopene, 21/69 with the fish oil, and 26/69 with a placebo.
  • There was no difference at all on IGF-1 expression level between the placebo and lycopene arms (p = 0.93) or on COX-2 expression between the placebo and the fish oil arms (p = 0.99) when baseline expression levels of these genes were compared to expression levels at 3 months.

It is obviously disappointing to get negative results to studies like this, when we would clearly like to be able to understand why some supplements and other dietary modifications seem to have beneficial effects in at least some men. However, …

The “New” Prostate Cancer InfoLink would like to see a broader and consistent set of studies of this type to try to clarify which of any nutritional supplements and dietary products have real biological effects in prostate cancer patients compared to a placebo (as opposed to in laboratory tests and in animal models). It is only through small studies of this type that we shall have a hope of clarifying whether such supplements or dietary modifications can make a real difference in the progression of low-risk prostate cancer in man.

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