Prostate Cancer and Fish Oil Supplementation - Absolutely No Association Demonstrated
By David Seaman, DC, MS, DABCN
Recently there has been a surge in media coverage regarding a study
that allegedly examined the effects of fish oil supplementation on
prostate cancer expression.1 Quite to the contrary, the subjects in this study were not
supplemented with fish oil or put on a fish-rich diet, which means it
is completely inappropriate to suggest that such would cause prostate
cancer.
The authors explain that they did a blood test on 834 subjects who
developed prostate cancer in the SELECT Trial and measured fatty acids
in plasma phospholipids.1 The SELECT Trial examined how supplemental selenium and vitamin E would impact the expression of prostate cancer.2 Table 1
outlines the outcome of that study. At most, there is a 1 percent
greater risk of developing prostate cancer if one supplements with
vitamin E. However, news reports that came out after SELECT was
published implied that vitamin E and selenium supplements are a cause
of prostate cancer. The appropriate conclusion is that these
supplements are ineffective as a monotherapy for prostate cancer
prevention.
Table 1: Original SELECT Trial Outcomes |
Supplement |
# of Subjects |
% Who Developed Cancer |
Placebo |
8,696 |
6.08 |
Vitamin E / Selenium |
8,707 |
6.37 |
Selenium only |
8,752 |
6.56 |
Vitamin E only |
8,737 |
7.09 |
A look at the details of the new prostate cancer-fatty acid study
reveals that a more appropriate conclusion is needed as well. As stated
above, the subjects were 834 individuals who developed prostate cancer
in
the SELECT Trial.
After a blood draw, the fatty acids were measured as a percentage of
total fatty acids in plasma phospholipids, and included omega-3, omega-6
and trans-fatty acids.
Table 2 outlines the average omega-3 fatty acid levels, which included eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
While the .04 percent higher level of EPA and the .1 percent higher
level of DHA in cancer subjects may be statistically significant, the
clinical relevance of such small differences remains unknown and was not
discussed in the paper. Despite this unknown, news reports
irresponsibly suggested that consuming fish and fish oil supplements may
be a cause of prostate cancer and that men should be careful not to eat
too much fish.
Table 2: Omega-3 Fatty Acids and Prostate Cancer? |
Fatty Acid |
% Subjects With Cancer |
% Subjects w/o Cancer |
EPA |
.65% |
.61% |
DHA |
3.01% |
2.91% |
The more appropriate conclusion would be that since controls and
prostate cancer patients have nearly identical plasma phospholipid
levels of omega-3 fatty acids, it is not likely that an association
between fatty acids and prostate cancer can be identified in this study.
Other dietary and lifestyle factors are likely to be involved. Consider
that prostate cancer is rare
in Inuit Eskimos consuming a traditional diet that includes extremely
large amounts of omega-3 fatty acids.
3
Unfortunately, the media scare about eating fish and taking fish oil
has been pervasive. Why would the media be so irresponsible? Either it
is due to ignorance and/or perhaps a new prostate-cancer treating /
preventing medication may be in the works. This notion may not be so
far-fetched; consider that statins are now often recommended as a preventive strategy for people with total cholesterol below 200 mg/dl.
References
- Brasky TM, Darke AK, Song X, et al. Plasma phosopholipid fatty acids and prostate cancer risk in the SELECT Trial. J Natl Cancer Inst, 2013 Jul 10. [Epub ahead of print]
- Klein EA, Thompson IM, Tangen CM, et al. Vitamin E and the risk of
prostate cancer. The Selenium and Vitamin E Cancer Prevention Trial
(SELECT). JAMA, 2011;306(14):1549-56.
- Dewailly E, Mulvad G, Pedersen HS, et al. Inuit are protected against prostate cancer. Cancer Epidemiol Bio Prev, 2003;12:926-27.
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