High levels of long chain omega-3 may increase prostate cancer risk: Study

By Nathan Gray

- Last updated on GMT

A high intake of omega-3 from food or supplements puts people in the highest risk category for aggressive prostate cancers, according to the new research.
A high intake of omega-3 from food or supplements puts people in the highest risk category for aggressive prostate cancers, according to the new research.

Related tags Omega-3 fatty acids Essential fatty acid Fatty acid Nutrition

A high intake of long-chain omega-3 fatty acids from foods and supplements could increase the risk the risk of developing aggressive prostate cancer by 71%, a new study has found.

The large-scale prospective study, published in the Journal of the National Cancer Institute, ​follows up on findings from 2011 which suggested that a high omega-3 status may be linked to prostate cancer​.

Led by senior author Dr Alan Kristal from Fred Hutchinson Cancer Research Center, USA, the new follow up study confirms the findings of the earlier research by analysing data from a in a large European population study - finding that high blood concentrations of long chain omega-3 polyunsaturated fatty acids (PUFAs) were linked to a 71% higher risk of developing high grade prostate cancer.

The study also found a 44% increase in the risk of low-grade prostate cancer and an overall 43% increase in risk for all prostate cancers.

"We've shown once again that use of nutritional supplements may be harmful,"​ said Kristal, who added that the findings of both the 2011 study and the recent research are surprising because omega-3 fatty acids are generally believed to have a host of positive health effects based on their anti-inflammatory properties.

"The consistency of these findings suggests that these fatty acids are involved in prostate tumorigenesis and recommendations to increase long-chain omega-3 fatty acid intake, in particular through supplementation, should consider its potential risks,"​ said the team.

"What's important is that we have been able to replicate our findings from 2011 and we have confirmed that marine omega-3 fatty acids play a role in prostate cancer occurrence,"​ said corresponding author Dr Theodore Brasky, of The Ohio State University Comprehensive Cancer Center - and lead author of the 2011 study.

"It's important to note, however, that these results do not address the question of whether omega-3's play a detrimental role in prostate cancer prognosis,"​ he said.

Study details

The new prospective study analysed data and specimens collected from men who participated in the Selenium and Vitamin E Cancer Prevention Trial (SELECT), a large randomised, placebo-controlled trial in Europe which aimed to test whether selenium and vitamin E, either alone or combined, reduced prostate cancer risk.

Using data from the SELECT study, the team analysed blood plasma omega-3 status for 834 men who had been diagnosed with prostate cancer - of which 156 were high-grade cancer - along with a comparison group of 1,393 men selected randomly from the 35,500 participants.

Compared with men with the lowest blood plasma levels of long chain omega-3 polyunsaturated fatty acids (PUFA) those with the highest levels had increased risks for low-grade (44% increased risk), high-grade (71% increased risk), and total prostate cancer (43% higher risk).

The team added that these associations were 'similar' for individual long-chain omega-3 fatty acids - noting that higher linoleic acid (omega-6) was associated with reduced risks of low-grade and total prostate cancer; but noting that there was no dose response.

The authors noted that it remains unclear from their results exactly why high levels of omega-3 fatty acids could increase prostate cancer risk, however, they suggested that replication of their finding in two large studies indicates the need for further research into possible mechanisms.

Two further articles have been published regarding this study on NutraIngredients, countering the claims made in this study. They can be found by clicking here​ and clicking here.

Sources: Journal of the National Cancer Institute
Published online ahead of print, doi: 10.1093/jnci/djt174
"Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial"
Authors: Theodore M. Brasky, Amy K. Darke, Xiaoling Song, et al

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1 comment

comments to fish oil and prostate cancer

Posted by Dr. Jim Vigue,

This latest study confirms a 2011 study when they took 3000 men out of 19,000 in the study to come up with their conclusion.

We should point out that even the 2011 study came up with this conclusion:

"Overall, the beneficial effects of eating fish to prevent heart diseases outweigh any harm related to prostate cancer risk."

The larger study I should point out had very few fish oil users. These were mostly men who ate a lot of fish. The study is interesting since it seems to be at odds with Japanese studies. Japanese men have among the highest omega Indices in the world averaging over 9% (The average index in the US and Europe is under 5). Japanese men have the highest average omega index and the lowest rate of prostate cancer. The Japanese also are the longest lived people in the industrialized world. Something seems to be wrong here somewhere. Japanese also have low fat diets.

It should also be noted that another study published in late 2011 in the journal Cancer Prevention Research reported diets supplemented with fish oil retarded prostate cancer growth. Examination of prostates in that study showed a reduced rate of cell proliferation in the fish oil supplemented group. These men were also on a low fat diet.

Whenever you take a small group like a few thousand people and just look at certain components of their diet or supplement use you can come up with all most any conclusion. Were genetic factors involved? How many men were smokers? How many men were overweight? What was their vitamin D level? Were they consumers of a lot of animal protein? How much fat did they consume? To conclude that omega 3s cause their cancer is a very aggressive assumption without knowing all the facts.

The conclusion we reach is if you are on a low fat diet, take various anti cancer supplements and maintain an omega Index of over 8% you maximize prostate as well as overall health.

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