Low fat diet + fish oil lowers risk for prostate cancer cell proliferation

Data from a prospective, randomized, Phase II clinical trial have shown that men diagnosed with early stage prostate cancer can decrease their risk for prostate cancer cell proliferation through use of a low-fat diet and fish oil capsules.

The newly reported study, just published by Aronson et al. in Cancer Prevention Research, was designed to test whether a decrease in dietary fat intake, combined with a fish oil supplement at a dose of 5 g/day, given for a period of 4-6 weeks prior to radical prostatectomy, would have measurable impact on biomarkers of prostate cancer development and progression by comparison with a “normal” Western diet (as a control).

The study used serum levels of insulin-like growth factor I (IGF-1)  as the primary study endpoint, but a whole range of other biomarkers were also assessed before and after surgery.

Here are the key data from the study:

  • 55 patients were initially randomized to the two study arms.
  • 48 patients actually completed the trial and provided data for analysis.
  • There was no difference in serum levels of IGF-1 between patients in the two study arms over the 4-6 week study period.
  • Compared to the men on the Western diet, men on the low-fat/fish oil diet demonstrated
    • Reduced levels of omega-6:omega-3 ratios in benign and malignant prostate tissue
    • Reduced prostate cancer proliferation, as indicated by a lower Ki-67 index
    • Reduced prostate cancer cell proliferation in a specialized bioassay test

It is potentially disappointing to see that this study did not achieve its primary endpoint. On the other hand, it is interesting to see that there was a clear reduction in the risk for cancer cell proliferation as a consequence of the change in diet and the addition of the fish oil supplement. These data do raise clear questions about the degree to which such dietary interventions may be able to lower the risk for progressive disease in men on active surveillance protocols. There have been many suggestions over the years that dietary interventions can affect risk for progression of lower-risk forms of prostate cancer, but we still have few good data from prospective studies of specific dietary interventions that allow us to make sound management recommendations.

A detailed media release from UCLA Health System provides additional information about this study and comments from the lead investigator.

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