Increased Flavonoid Intake Reduced Risk for Aggressive Prostate Cancer

This abstract will be presented at a press conference hosted by program chairperson Cory Abate-Shen, Ph.D., the Michael and Stella Chernow professor of urological oncology and associate director of the Herbert Irving Comprehensive Cancer Center at Columbia University Medical Center, in the San Simeon AB Room on the fourth floor of the Hilton Anaheim at 7:30 a.m. PT on Wednesday, Oct. 17. Reporters who cannot attend in person can call in using the following information:

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Newswise — ANAHEIM, Calif. — A high total intake of flavonoids, a group of compounds found in plants, was inversely associated with the risk for highly aggressive prostate cancer, according to data presented at the 11th Annual AACR International Conference on Frontiers in Cancer Prevention Research, held here Oct. 16-19, 2012.

“Incorporating more plant-based foods and beverages, such as fruits, vegetables, herbs and tea, into the diet may offer some protection against aggressive prostate cancer,” said Susan E. Steck, Ph.D., M.P.H, R.D., associate professor at the Arnold School of Public Health at the University of South Carolina. “Filling your plate with flavonoid-rich foods is one behavior that can be changed to have a beneficial impact on health.”

Prior preclinical studies have shown that flavonoids have beneficial effects against prostate cancer, but few studies have examined the effect of flavonoids on prostate cancer in humans.

Steck and her colleagues used data from 920 African-American men and 977 European-American men in the North Carolina–Louisiana Prostate Cancer Project who were newly diagnosed with prostate cancer. Participants completed a self-reported dietary history questionnaire to assess flavonoid intake, which was measured using the U.S. Department of Agriculture’s 2011 Database for the Flavonoid Content of Selected Foods.

Men with the highest total intake of flavonoids had a 25 percent lower risk for aggressive prostate cancer compared with those men with the lowest flavonoid intake.

“We found that higher total flavonoid intake was associated with reduced odds for aggressive prostate cancer in both African-American and European-American men, but no individual subclass of flavonoids appeared to be protective independently, suggesting that it is important to consume a variety of plant-based foods in the diet, rather than to focus on one specific type of flavonoid or flavonoid-rich food,” Steck said.

In addition, the risk for aggressive prostate cancer was even lower in those men younger than 65 and in current smokers with the highest levels of flavonoid intake. Dietary questionnaire results revealed that citrus fruits and juices, such as oranges and grapefruits, tea, grapes, strawberries, onions and cooked greens were the top contributors to total flavonoid intake among the participants.

“The results support public health recommendations and guidelines from organizations such as the American Institute for Cancer Research to consume a more plant-based diet,” Steck said. “In particular, consuming more flavonoid-rich foods may be beneficial for those people who are at increased risk for cancer, such as smokers.”

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Abstract:A103 Flavonoid intake and prostate cancer aggressiveness among African Americans and European Americans in PCaP. Rebecca R. George(1), Susan E. Steck(1), L. Joseph Su(2), James L. Mohler(3), Elizabeth T.H. Fontham(4), Jeannette T. Bensen(5), James R. Hebert(1), Hongmei Zhang(1), Lenore Arab(6). (1)University of South Carolina, Columbia, SC, (2)National Cancer Institute, Bethesda, MD, (3)Roswell Park Cancer Institute, Buffalo, NY, (4)Louisiana State University Health Sciences Center, New Orleans, LA, (5)University of North Carolina at Chapel Hill, Chapel Hill, NC, (6)University of California, Los Angeles, CA.

Background: Flavonoids are phytochemicals that are present in plant-based foods such as tea, wine, fruits, vegetables, and cocoa. Animal and cell culture studies indicate a chemopreventive effect of flavonoids on prostate cancer via mechanisms related to anti-inflammation, induction of apoptosis, antioxidation, cell cycle regulation, and impairment of angiogenesis. However, few epidemiological studies have examined associations between flavonoid intake and prostate cancer in humans. Methods: Data from 920 African-American (AA) and 977 European-American (EA) newly-diagnosed prostate cancer patients from the North Carolina-Louisiana Prostate Cancer Project (PCaP) were used to assess the association between flavonoid intake and prostate cancer aggressiveness. Diet was assessed using a modified version of the National Cancer Institute (NCI) Diet History Questionnaire. The USDA recently released the 2011 USDA Database for the Flavonoid Content of Selected Foods, which allowed for estimation of intake of five subclasses of flavonoids that were summed to calculate total flavonoid intake. Men were classified as cases (high aggressiveness) if Gleason sum ≥8, or PSA >20 ng/ml, or Gleason sum ≥7 AND clinical stage = T3c-T4c. All other men constituted the comparison group (low and intermediate aggressiveness). Odds ratios (OR) and 95% confidence intervals (95%CI) were calculated for high aggressiveness prostate cancer by tertile of flavonoid intake using logistic regression with adjustment for potential confounders. Results: The highest tertile (compared to the lowest tertile) of total flavonoid intake appeared to be inversely associated with prostate cancer aggressiveness after adjustment for age, race, education, smoking status, and screening history (OR=0.75, 95%CI= 0.54, 1.04). Estimated odds of high aggressiveness prostate cancer with increasing flavonoid intake were reduced further by smoking and age, such that inverse associations were strongest in men <65 years of age (OR=0.62, 95%CI=0.40, 0.98 and OR=0.67, 95%CI=0.42, 1.06 for the middle and highest tertiles, respectively) and in current smokers (OR=0.25, 95%CI=0.11, 0.54 and OR=0.48, 95%CI=0.22, 1.06 for the middle and highest tertiles, respectively). Results did not differ by race. Orange and grapefruit juices and tea were the main contributors to total flavonoid intake in both AA and EA men. Conclusions: Total flavonoid intake was inversely associated with prostate cancer aggressiveness in this large case-only study. Stratified analyses revealed that current smokers and younger men may receive the most benefit from increased flavonoid intake. This study provides clinical evidence that suggests a plant-based diet may prevent aggressive prostate cancer.