Study: DHA increases aggressive prostate cancer risk

Bonnie - make sure you read my comments below.

Analyzing data from a nationwide study involving more than 3,400 men, researchers at Fred Hutchinson Cancer Research Center found that men with the highest blood percentages of docosahexaenoic acid, or DHA, an inflammation-lowering omega-3 fatty acid commonly found in fatty fish, have two-and-a-half-times the risk of developing aggressive, high-grade prostate cancer compared to men with the lowest DHA levels. Conversely, the study also found that men with the highest blood ratios of trans-fatty acids -- which are linked to inflammation and heart disease and abundant in processed foods that contain partially hydrogenated vegetable oils -- had a 50 percent reduction in the risk of high-grade prostate cancer. In addition, neither of these fats was associated with the risk of low-grade prostate cancer risk. The researchers also found that omega-6 fatty acids, which are found in most vegetable oils and are linked to inflammation and heart disease, were not associated with prostate cancer risk. They also found that none of the fats were associated with the risk of low-grade prostate cancer.

These findings by were published in the American Journal of Epidemiology. The study was based on data from the Prostate Cancer Prevention Trial, a nationwide randomized clinical trial that tested the efficacy of the drug finasteride to prevent prostate cancer. While the trial involved nearly 19,000 men age 55 and older, the data in this analysis came from a subset of more than 3,000 of the study participants, half of whom developed prostate cancer during the course of the study and half of whom did not. Among the study participants, very few took fish oil supplements -- the most common non-food source of omega-3 fatty acids. The majority got omega 3s from eating fish.

The researchers insist that overall, the beneficial effects of eating fish to prevent heart disease outweigh any harm related to prostate cancer risk. Yet they have no explanation for the weird findings.

Bonnie - there are several aspects of this study to take into consideration:

1) These subjects were on finasteride (Propecia, Proscar). There have been no safety studies on how this drug works in relation to other medications, much less how it interacts with dietary nutrients. Maybe finasteride has a weird effect when it interacts with certain dietary fats.

2) Virtually none of these subjects were on omega-3 dietary supplements.

3) It very unusual that a small group of subjects had high DHA levels only. In most fish, as there is in most fish oil supplements, a healthy balance of EPA to DHA (more EPA than DHA) exists. The researchers have no explanation for the high DHA levels.

4) Whenever there is a fat imbalance, even within the omega-3 subset, there is a risk for a biochemical imbalance. Do I believe that these high DHA subjects would be subject to a two and a half greater risk of aggressive prostate cancer. Not a chance. There has to be some connection with finasteride or another confounding factor.

5) What makes the study even more questionable is that trans-fat, which is well-known for creating a host of health issues, including heart disease and just recently, male infertility, would actually reduce the risk for aggressive prostate cancer. In addition, omega-6 fatty acids, some of which are considered inflammatory fatty acids, did not increase aggressive cancer risk.

6) There have been numerous studies over the last decade showing the effectiveness of omega-3 fatty acids for reducing prostate cancer risk. I cannot say that I have seen one showing DHA alone helps or harms, however. The studies have always been with EPA and DHA together.

In the event there there is merit to this study, here are my recommendations:

1) If you are an older male, do not take consume DHA in high amounts by itself. Always consume as EPA/DHA, which 99.9% of you do already.

2) If you take finasteride (Propecia or Proscar), you may want to test your DHA levels to make sure they are not high. If the DHA level happens to be high, I would look to wean off finasteride (with assistance from a licensed health professional) as opposed to stopping consumption of fish and fish oil supplements. Balancing your EPA and DHA levels can be accomplished pretty easily.