Low-Fat Fish Oil Diet May Alter Prostate Tumor Biology

Fish oil supplements

Men with early-stage prostate cancer who ate a low-fat diet supplemented with fish oil had lower amounts of pro-inflammation molecules in their blood and lower prostate tumor cell proliferation compared with men who ate a high-fat Western diet.

Men on the low-fat fish oil diet had lower serum levels of omega-6 fatty acids and high levels of serum omega-3 fatty acids compared with the prostate cancer patients who consumed a Western diet. The experimental group also had lower levels of the pro-inflammatory eicosanoid 15(S)-hydroxyeicosatetraenoic acid, or 15(S)-HETE, which has been previously shown to be associated with cancer. The decline in mean 15(S)-HETE was 7.2% in the low-fat diet group compared with 24.7% in the high-fat diet group (P = .02). The men in the low-fat diet group also had a lower cell cycle progression score, a marker for the aggressiveness of a cancer.

The results suggest that diet, even in the short term, can affect the biology of both healthy and cancer tissue in the body. Further studies are needed to support this claim.

A lower cell cycle progression score may help prevent prostate cancer from becoming faster growing and more aggressive, said lead author William Aronson, MD, clinical professor of urology at UCLA, in a statement.

The results of the study are published in Cancer Prevention Research.

Using mouse models, researchers have previously shown that boosting consumption of omega-3 rich fish oil and decreasing corn oil consumption can delay both the development and progression of prostate cancer in xenografts. But the clinical data on fatty acid intake has been mixed. Some epidemiologic studies found that men who consumed a diet high in fat but low in omega-3 fatty acids have a higher risk of developing prostate cancer and advanced disease, but other studies found no such correlation.

Omega-6 fatty acids are used to produce pro-inflammatory eicosanoids while omega-3 fatty acids do not have the same inflammatory characteristics.

The current study is a post-hoc analysis of a previously published phase II study from 2011 analyzing serum and tissue samples from men with early prostate cancer who were randomized to either a low-fat diet (15% of calories from fat) and 5 mg of fish oil per day or a Western diet with 40% of calories coming from fat (typical of the American diet and including high levels of omega-6 fatty acids from corn oil) prior to their prostatectomy. A total of 48 patients completed the trial. The study showed that patients consuming a low-fat diet had slower growing cancer cells compared with those who consumed a high-fat diet, and that men on the low-fat diet actually had changes in their cell membrane in both healthy and cancer tissue. The authors also found that the low-fat fish oil diet for 4 to 6 weeks resulted in a lower omega-6 to omega-3 fatty acid ratio, but did not alter serum IGF-1 levels. According to Aronson, these changes may directly affect the biology of the cells.

The new analysis shows that a decrease in the pro-inflammatory eicosanoid correlated with changes in Ki67, a proliferation marker. But this inflammation molecule did not correlate with the cell cycle progression score.

Aronson and colleagues also analyzed leukotriene B4 (LTB4), a pro-inflammatory molecule, in the samples from patients. They found that LTB4 levels in the blood were lower after the low-fat diet (P = .036) and that these levels correlated with lower cell cycle progression scores (P = .03).

The study authors are now working on the biological mechanism of how LTB4 may affect prostate cancer cells, including how LTB4 binds to receptors on the surface of prostate cancer cells.