Change in Western diet may reduce PSA levels, prostate cancer growth

If the fatty acid ratio found in the typical Western diet is changed to include more omega-3 fatty acids and fewer omega-6 fatty acids, then prostate cancer tumor growth rates and PSA levels may decrease, according to a preclinical study published recently in Clinical Cancer Research (2006; 12:4662-70).

In an animal study, researchers compared tumor cell growth rates and PSA levels in two groups of mice. One group was fed a diet of 20% fat with a healthy one-to-one ratio of omega-6 and omega-3 fatty acids, while the second group was fed a diet of 20% fat, but with most of the fat coming from omega-6 fatty acids. In a Western diet, omega-6 is found in corn, safflower oils, and red meat, while omega-3 can is found in cold-water fish, such as salmon, tuna, and sardines.

Investigators found that tumor cell growth rates decreased by 22%, and PSA levels were 77% lower in the mice with a healthier balance of fatty acids compared with the mice receiving mostly omega-6 fatty acids. Researchers believe the decrease in growth rates is due to increases in omega-3 fatty acids DHA and EPA and a concomitant reduction of the omega-6 fatty acid arachidonic acid. Cyclooxgenase enzymes (COX-1 and COX-2) convert the three competing fatty acids into prostaglandins, which can be either pro-inflammatory and increase tumor growth or anti-inflammatory and reduce growth.

Pro-inflammatory prostaglandin levels in tumors were 83% lower in mice eating the healthy diet than in those eating the high-omega-6 diet.

“This is one of the first studies showing changes in diet can impact the inflammatory response that may play a role in prostate cancer tumor growth,” said principal investigator William Aronson, MD, of the UCLA Jonsson Cancer Center. “We may be able to use EPA and DHA supplements, while also reducing omega-6 fatty acids in the diet as a cancer prevention tool or, possibly, to reduce progression in men with prostate cancer.”