Low fat diet with fish oil slowed growth of human prostate cancer cells

http://www.eurekalert.org/pub_releases/2011-10/uoc--yaw102411.php

Public release date: 25-Oct-2011
Contact: Kim Irwin
University of California - Los Angeles Health Sciences
You are what you eat: Low fat diet with fish oil slowed growth of human prostate cancer cells

A low-fat diet with fish oil supplements eaten for four to six weeks prior to prostate removal slowed down the growth of prostate cancer cells -- the number of rapidly dividing cells -- in human prostate cancer tissue compared to a traditional, high-fat Western diet.

Done by researchers at UCLA's Jonsson Comprehensive Cancer Center, the short-term study also found that the men on the low-fat, fish oil supplement diet were able to change the composition of their cell membranes in both the healthy cells and the cancer cells in the prostate. They had increased levels of omega-3 fatty acids from fish oil and decreased levels of omega-6 fatty acids from corn oil in the cell membranes, which may directly affect the biology of the cells, though further studies are needed, said Dr. William Aronson, the study's first author and a researcher with UCLA's Jonsson Comprehensive Cancer Center.

The study also found that blood obtained from patients after the low-fat, fish oil diet program slowed the growth of prostate cancer cells in a test tube as compared to blood from men on the Western diet, which did not slow cancer growth.

"The finding that the low-fat, fish oil diet reduced the number of rapidly dividing cells in the prostate cancer tissue is important because the rate at which the cells are dividing can be predictive of future cancer progression," Aronson said. "The lower the rate of proliferation, the lesser the chances that the cancer will spread outside the prostate, where it is much harder to treat."

The study appeared Oct. 25, 2011 in Cancer Prevention Research, a peer-reviewed journal of the American Association for Cancer Research.

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Diet studies often are difficult to evaluate because getting patients to comply with dietary changes can be challenging. However, the food eaten by men in both arms of this study was precisely controlled, Aronson said. The meals were prepared by chefs in the UCLA Clinical Translational Research Center and delivered in bulk to study participants several times a week. Participants also met with a dietician, kept food diaries and were required to return uneaten food.

"The key to this study was having the meals prepared and delivered to the study participants," Aronson said. "This resulted in a very high rate of compliance, making the study very well controlled."

The Western diet consisted of 40 percent of calories from fat, generally equivalent to what many Americans consume today. The fat sources also were typical of the American diet, and included high levels of omega-6 fatty acids from corn oil and low levels of fish oil that provide omega-3 fatty acids.

The low-fat diet consisted of 15 percent of calories from fat. Additionally, the men on this diet took five grams of fish oil per day in five capsules, three with breakfast and two with dinner, to provide fish oil omega-3 fatty acids. Omega-3 fatty acids have been found to reduce the incidence of heart disease and fight inflammation, and inflammation has been associated with certain cancers.

"Preclinical studies suggest that lowering dietary omega-6 fatty acids from corn oil and increasing omega-3 fatty acids from fish oil decreases the risk of prostate cancer development and progression," the study states. "We found this diet intervention resulted in a decrease in omega-6 vs. omega-3 fatty acid ratios in benign and malignant prostate tissue and a decrease in malignant cell proliferation."

Aronson cautioned that he could not recommend dietary changes based on this study because of its short duration and small sample size. However, based on these results he is organizing a much larger study of 100 men with prostate cancers who have elected active surveillance, meaning they're not getting any treatment for their disease but are getting regular biopsies and check-ups.

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