A study conducted by researchers at cancer centers across the US has found a link between omega 3 fatty acids and an increased risk of prostate cancer. Omega 3 fatty acids are found in fish including salmon, trout, and fresh tuna, and in fish oil supplements.

Omega 3 and Cancer

Because omega-3 fatty acids (including DHA and EPA found in fish) decrease inflammation, researchers have long believed that these nutrients would also decrease cancer. In fact, Dr. Alan Kristal, Associate Head of the Cancer Prevention Program at Fred Hutchinson Cancer Research Center in Seattle, expected just that result when he authored two studies, one in 2011 and one just published in the Journal of the National Cancer Institute on the effect of fish oil and prostate cancer. But the studies revealed just the opposite.  Indeed, they pointed to an increased risk of advanced prostate cancer of over 70 percent in men who had high levels of long-chain omega-3 fatty acids in their blood.

The Study

The study, published online July 10 in the Journal of the National Cancer Institute, looked at blood levels of omega-3 fatty acids in some of the men enrolled in the Selenium and Vitamin E Cancer Prevention Trial (SELECT) of more than 35,000 men over age 50 in the US, Puerto Rico, and Canada. The study did not collect information on the men’s diets. Therefore, it’s not clear whether the omega-3 fatty acids in their blood came from food or from supplements.

The Results

The analysis compared 834 men from the trial who had been diagnosed with prostate cancer to a comparison group of 1,393 men selected randomly from all 35,000 participants. The researchers expected to find a protective factor from the presence of omega-3 fatty acids in the blood. Instead, they found that those with the highest levels of omega-3 fatty acids had a 43% higher risk of developing prostate cancer, and a 71% higher chance of developing high-grade prostate cancer, which is more likely to be fatal. Previous studies found similar results.