Low Fat Diet with Fish Oil Supplementation For Prostate Cancer

by | Dec 1, 2011 | 2011, Cancer, Fish Oil Supplements, Men's Health - Prostate, Prostate Cancer

Written by Marcia J. Egles, MD. Of the 48 overweight or obese patients with prostate cancer, those who went on a 4-6 week low-fat, high Omega-3 fish oil supplement diet had a significant 32.2 % reduction in a marker for cancer growth compared to the Western diet group.

As reported in a recent preliminary clinical trial from the University of California-Los Angeles, a low-fat diet combined with fish oil supplementation may favorably affect prostate cancer cell biology (1). The prostate is the gland below a man’s bladder that produces fluid for semen. Prostate cancer is the second most common cause of cancer death in men. Prostate cancer is rare in men younger than 40, but present in up to 80% of men over the age of 80 (2).

Prior laboratory studies in human prostate cancer cells and in mice have shown that reducing dietary fat and decreasing the ratio of omega-6 to omega-3 fatty acids may delay the progression of prostate cancer (3,4).  Omega-6 and omega-3 polyunsaturated fatty acids (PUFA) are both essential to the human diet, but omega-6 fatty acids are far more abundant in foods than omega-3’s. One source of omega-3 fatty acids is marine fish oil.  Some human population studies have reported that a high-fat diet combined with a low intake of omega-3 fatty acids is associated with an increased risk of developing prostate cancer ( 5,6,7), although other studies do not support this association (8).

In the new study (1), men who were scheduled for radical prostate removal  surgery volunteered to follow dietary interventions for four to six weeks prior to their surgery.   Radical prostatectomy is a prostate cancer treatment which involves the complete removal of the prostate and some of its surrounding tissue.  Fifty-five patients were randomly assigned to either a high fat “Western diet” or to a low-fat, high omega-3 fish oil supplemented diet.  The tissue later obtained from the prostate surgeries was then examined and compared between the two groups. The average age of the men was 60 years in both groups.  The majority of the men were overweight or obese.  The baseline diets of the participants overall had omega-6 to omega-3 ratios of about 10:1.   Forty-eight men completed the study.

More specifically, the Western diet provided 40% of its calories from fat, 15% from protein and 45% from carbohydrates.  The omega-6 to omega-3 ratio was 15:1.  The low-fat/fish oil diet was 15% fat, 15% protein, and 70% carbohydrates.  The subjects took five 1.1 gram fish oil capsules daily which, combined with the low-fat diet, lowered their omega-6 to omega-3 ratio to 2:1.  For dietary control, all the meals were prepared at the UCLA Clinical Research Center and delivered to the patients’ homes.

Many comparative analyses were conducted on the prostatic tissues from the two groups.  One important biological marker of cancer growth, as measured by Ki-67 immunostaining, showed significant  32.2 % (p less than 0.05) reduction in the low-fat/fish oil group versus the Western diet group.  This marker has been shown to predict recurrence after prostatectomy and prostate cancer survival (9, 10 ).

Additionally, changes in the fatty acid-composition of the cell membranes between the two groups were observed in both benign and malignant tissue.   Subjects in the low-fat/fish oil group had lower omega-6 levels and higher omega-3 levels in the prostate tissue cell membranes relative to the Western diet group.  The fatty acid composition of cell membranes is believed to play an important role in the signaling pathways leading to cancer development and progression ( 3,11).

This small, brief trial suggests that changes in dietary fat can influence the fatty acid composition of prostatic tissue and potentially reduce prostatic cancer growth.  The researchers expressed that further studies are warranted to evaluate alteration of quantity and quality of dietary fat on tumor biology and cancer prevention (1).

Source: Aronson, William J., et al. “Phase II prospective randomized trial of a low-fat diet with fish oil supplementation in men undergoing radical prostatectomy.” Cancer prevention research 4.12 (2011): 2062-2071.

© 2011 American Association for Cancer Research.

Posted December 1, 2011.

References:

  1. Aronson, William J. et al . Phase II Prospective Randomized Trial of a Low-Fat Diet with Fish Oil Supplementation in Men Undergoing Radical Prostatectomy Cancer Prevention Research.  Published OnlineFirst October 25, 2011; doi: 10.1158/1940-6207.CAPR-11-0298
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