Diets bolstered by more vegetables produced no extra protection from the increased micronutrients
- Roswell/UCSD team: Vegetable-rich diet didn’t benefit men with prostate cancer
- Surprising finding runs contrary to prevailing scientific and public opinion
- Increased vegetable intake may still help cancer patients to tolerate treatment
BUFFALO, N.Y. — National guidelines recommend that men with prostate cancer eat a vegetable-rich diet, suggesting it might decrease cancer progression and death. But in a phase III randomized clinical trial, patients with prostate cancer assigned to eat seven or more servings of vegetables and fruits daily saw no extra protection from the increased consumption of micronutrients.
“These data indicate that, despite prevailing scientific and public opinion, eating more vegetables will not alter the course of prostate cancer. It will not, to the best of our knowledge, suppress or cure it,” says J. Kellogg Parsons, MD, MHS, Professor of Urology at the University of California San Diego School of Medicine and Moores Cancer Center and study lead investigator. “However, while eating a healthy diet rich in fruits and vegetables and getting more exercise may not cure cancer, it may keep the body stronger and healthier, which may help patients tolerate cancer treatments.”
The Men’s Eating and Living (MEAL) study, published January 14, 2020, in the Journal of the American Medical Association and led by UC San Diego Moores Cancer Center and Roswell Park Comprehensive Cancer Center investigators, enrolled 478 men aged 50 to 80 years at 91 sites in the United States. The patients had been diagnosed with early-stage prostate adenocarcinoma and enrolled in an active surveillance program in which patients defer immediate treatment until the disease advances.
Patients were randomized to a control group that received written information about diet and prostate cancer or to a telephone counseling behavioral intervention program that encouraged participants to eat foods high in carotenoids, such as leafy greens, carrots and tomatoes, and cruciferous vegetables such as broccoli and cabbage. Both groups were monitored for two years.
“Patients assigned to the intervention increased their intake of fruits and vegetables to a statistically significant degree, and significantly more than control patients did. These findings were supported by significant changes in the blood carotenoid levels of patients. Nonetheless, these data fail to support prevailing assertions in clinical guidelines and the popular media that diets high in micronutrient-rich vegetables improve cancer-specific outcomes among prostate cancer survivors,” says James Marshall, PhD, Distinguished Professor with the Department of Cancer Prevention and Population Sciences at Roswell Park, co-senior author on the study along with John Pierce, PhD, Professor Emeritus of Cancer Prevention at UC San Diego School of Medicine.
The study is the first randomized clinical trial to test the effect of dietary intervention on prostate cancer. It was conceived based on preliminary scientific data and on inquiries from patients who wondered if a change in diet would influence their diagnosis or treatment.
“The most common question I receive from men on active surveillance is, ‘Can I decrease the chances that I will need treatment for prostate cancer by changing my diet?’ We now have good evidence that a diet rich in fruits and vegetables and light on red meat is not likely to impact need for treatment,” says co-author James Mohler, MD, Professor of Oncology with Roswell Park’s Department of Urology. “But this study does not provide justification for eating anything you want, either. The overall health benefits of a diet that’s relatively low in fat and rich in fruits, vegetables and healthy grains are well-established.”
The impact of nutrition on diseases is an ongoing conversation among researchers and clinicians. Scientific studies have identified a strong role for changing diet to improve outcomes in diabetes and cardiovascular disease, but not in cancer.
Although the MEAL study revealed no positive impact on prostate cancer, it did demonstrate that behavioral modification can lead patients to make healthier food choices.
“We designed a simple and inexpensive program that proved we could change people’s diets for the better. We hoped that through nutrition we could alter disease outcomes and then use those data to build a network of diet counselors to help men with prostate cancer eat more vegetables,” says Dr. Parsons. “It’s still an endeavor worth considering, possibly in patients with advanced prostate cancer.”
Additional co-authors include Donna E. Hansel, Loki Natarajan, Martha White and Sheri Hartman, UC San Diego; David Zahrieh, Heshan Liu and Elizabeth M. Storrick, Mayo Clinic; Electra Paskett, Ohio State University; Adam Kibel, Harvard Medical School; Olwen Hahn and John Taylor, University of Chicago; Sean Stroup, Naval Medical Center San Diego; Peter Van Veldhuizen, Midwest Oncology Associates; Lannis Hall, Washington University; Eric Small, UC San Francisco; and Michael Morris, Memorial Sloan Kettering Cancer Center.
Funding for this research came, in part, from the National Institutes of Health/National Cancer Institute (UG1CA189823 Alliance for Clinical Trials in Oncology NCORP Grant, U24CA196171, U10CA037447, U10CA011789, U10CA041287, U10CA059518, U10CA077651, U10CA077658, U10CA138561, U10CA180791, U10CA180850, U10CA180866, U10CA180830, SWOG grant U10CA180888) and R01CA132951-01A1), the U.S. Department of Defense (grant PC073412), The Prostate Cancer Foundation and William Hamilton.
The study is available at https://jamanetwork.com/journals/jama/fullarticle/2758598.
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Annie Deck-Miller, Senior Media Relations Manager