Prostate Cancer – A Fish Tale

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Have you heard that fish oil supplements cause prostate cancer? The news items come from an article published online July 11, 2013 by Brasky et al. in the Journal of the the National Cancer Institute, “Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial.

This study looked at 834 men diagnosed with prostate cancer, and compared them with 1393 men, matched for age and race, that did not have prostate cancer. They then looked at the amount of omega-3 in their blood and compared the groups.

They found that those with the highest omega-3 levels had the highest risk of prostate cancer, 44% higher over all. This study followed up on one published earlier by the same group that suggested increased risk from fish consumption. The levels of omega-3 in the highest group were fairly modest, equivalent to eating an oily fish, such as salmon, twice a week.

Before jumping to the conclusion that men should not take fish oil or consume much fish, there are a number of things to consider. First of all, association does not imply causation. What does that mean? Just because two things occur together, it does not mean that one caused the other. If you look outside on a rainy day, you will see many people carrying umbrellas. But you would be wrong to conclude that carrying umbrellas caused it to rain.

It could be that it wasn’t the omega-3 in fish, or fish oil supplements, that caused prostate cancer, but rather something else in the products, such as mercury or other toxins in the fish. If you ate fish raised in places low in pollution, or consumed ultra-filtered fish oil, then perhaps it would not be a problem. This study does not answer that question.

Even if eating fish or taking supplements increases the risk of prostate cancer, studies have shown it decreases the risk of cardiovascular (heart) disease, which is far more common.

This study was not the preferred double-blind, placebo controlled study, and the conclusion may just be wrong. After all, other studies have shown that fish consumption decreases prostate cancer. For example, one in the Lancet showed decreased risk of prostate cancer in those who ate moderate or high amounts of fish. Also consider that Japanese men consume much more fish then American men, yet have far less prostate cancer.

So until I see more convincing evidence, I’ll continue to take my fish oil capsules, and enjoy eating salmon.

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About Daniel Ginsberg, MD, FACP

I'm an internal medicine physician and have avidly applied computers to medicine since 1986, when I wrote my first medically oriented computer programs. So yes, that means I'm at least 25-years-old!
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2 Responses to Prostate Cancer – A Fish Tale

  1. David says:

    thanks for sharing! Prostate cancer is a form of cancer that men can acquire. It can be described as being a malignant growth or tumor that is made up of cells that affect the prostate gland. In most cases, the tumor will grow at a slow rate and will not spread any further than the gland for a number of years. During this span of time, the growth may not show any outward symptoms. Even upon a physical examination, it may not be obvious that a problem exists. Thank you and your helpers for all the research and information. :D

  2. BioPhys says:

    Daniel, here is another thing to considder. The lowest quality of fish oil always goes into the capsules. This because old and oxidized fish oils taste nasty. Nonoxidized oils taste nothing and are normally consumed right out of portion package. Use of low quality fish oils in capsules could therefore also possibly be the cause of the effects in this study. Oxidized Omega 3 fatty acids contains high levels of Peroxides which can be considdered as a free radical. These molecules react readily with DNA… But It have been known for decades that free radicals increase the risk of cancer (this regardless of if the free radicals comes from excessive UV radiation exposure, poluted food, etc). In other words the study basically proves nothing but the obvious… which is, if you eat free radicals expect an increased risk of getting cancer.

    How to avoid this problem and still getting healthy effective nonoxidized Omega 3? Well, skip the capsules. There is fare too poor control of the quality and oxidation level of the oil going into those capsules. Therefore, take your omega 3 in form of vacuum packed or portion sized fish oil. Myself I use low oxidized Cod Liver Oil (CLO) from Vesteraalens.no . They have delivered fish products for more than 100 years now and seem to have pretty good knowledge of this stuff.

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