The counter intuitive findings come from a study published in American Journal of Epidemiology. The research analyzed data from a nationwide study involving more than 3,400 men.
Researchers from the Fred Hutchinson Cancer Research Center found men with the highest blood percentages of docosahexaenoic acid (DHA), had 2.5 times the risk of developing aggressive, high-grade prostate cancer compared to men with the lowest DHA levels.
Cause for concern?
Researchers led by Dr Theodore Brasky said that men concerned about heart disease should not reduce their omega-3 intake in response to the cancer link.
“Overall, the beneficial effects of eating fish to prevent heart disease outweigh any harm related to prostate cancer risk,” added Brasky.
“What this study shows is the complexity of nutrition and its impact on disease risk, and that we should study such associations rigorously rather than make assumptions,” he said.
Conversely, the study found that men with the highest blood ratios of trans-fatty acids had a 50 percent reduction in the risk of prostate cancer.
“Omega-3 fatty acids, considered beneficial for coronary artery disease prevention, may increase high-grade prostate cancer risk, whereas trans-fatty acids, considered harmful, may reduce high-grade prostate cancer risk,” said the authors, led by Dr Theodore Brasky.
“We were stunned to see these results and we spent a lot of time making sure the analyses were correct,” said Brasky.
“Our findings turn what we know – or rather what we think we know – about diet, inflammation and the development of prostate cancer on its head and shine a light on the complexity of studying the association between nutrition and the risk of various chronic diseases,” he added.
Chronic inflammation is known to increase the risk of several cancers, and has an important role the development and progression of prostate cancer.
Omega-3 fatty acids found primarily in fish and fish oil supplements have anti-inflammatory effects, whilst other fats, such as the omega-6 fats in vegetable oil and trans-fats found in fast foods, are thought to promote inflammation.
The study examined the associations between these inflammation-related fatty acids and the prevalence of prostate cancer over seven years, in a nested case-control analysis of participants from the Prostate Cancer Prevention Trial.
“We wanted to test the hypothesis that the concentrations of these fats in blood would be associated with prostate cancer risk,” said Brasky.
“Specifically, we thought that omega-3 fatty acids would reduce and omega-6 and trans-fatty acids would increase prostate cancer risk,” he explained.
The research study, which claims to be the largest ever to examine the association of dietary fats and prostate cancer risk tested fatty acid levels from the blood serum, measuring the concentrations of omega-3, omega-6, and trans-fatty acids.
The researchers found that none of the fats were associated with the risk of low-grade prostate cancer risk. However, Brasky and his co-workers reported that docosahexaenoic acid (DHA) was positively associated with high-grade prostate cancer.
In contrast, they found omega-6 fatty acids were not associated with prostate cancer risk, whilst trans-fats (TFA) were seen to be inversely associated with risk of high-grade prostate cancer; showing a 50 percent reduction in risk.
Brasky and his colleagues said that their findings show a significant association between inflammation-related phospholipid fatty acids and the risk of prostate cancer risk, “albeit in the directions opposite to those hypothesized.”
Source: American Journal of Epidemiology
Published online ahead of print, doi: 10.1093/aje/kwr027
“Serum Phospholipid Fatty Acids and Prostate Cancer Risk: Results From the Prostate Cancer Prevention Trial”
Authors: T.M. Brasky, C. Till, E. White, M.L. Neuhouser, X. Song, et al