Study participants with prostate cancer who reported the highest amounts of plant-based foods in their diets had a 52% lower risk of the cancer progressing and a 53% lower risk of recurrence compared to those who had the lowest amounts of plants in their diets.

The diet assessments were based on questionnaires of food consumption given to people enrolled in the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) study.

The study was presented at the 2023 American Society of Clinical Oncology (ASCO) Genitourinary Cancers Symposium, February 16-18, 2023, in San Francisco, California.

In 2023, an estimated 288,300 new cases of prostate cancer will be diagnosed in the U.S. and 34,700 people will die from the disease.

Risk factors for the disease include older age, African ancestry, a family history of the disease, and certain inherited genetic conditions. 

Smoking and excess body weight may increase the risk of aggressive or deadly disease.

“While not all diets are equal in terms of modifiable risk factors for prostate cancer progression, we hope these results guide people at risk to make better, more healthful choices across their entire diet,” said Vivian Liu, Clinical Research Coordinator, Osher Center for Integrative Health, University of California, San Francisco, and lead study author.

“We’ve known that diets that include vegetables, fruits, legumes, and whole grains are associated with numerous health benefits, including a reduction in diabetes, cardiovascular disease, and overall mortality. We can now add benefits in reducing prostate cancer progression to that list.”

About the Study

Decades of observational studies have found that foods such as tomatoes appear to reduce prostate cancer incidence and mortality.

However, less is known about plant-based dietary patterns and prostate cancer survivorship, which is why the CaPSURE Diet and Lifestyle (CDL) sub-study was started in 2004.

People who were enrolled in CaPSURE and completed a diet and lifestyle questionnaire comprised the participants in this study.

All of the study participants had early to mid-grade prostate cancer.

They completed food frequency questionnaires about how much and how often they consumed approximately 140 different foods and beverages.

The diet indices (an overall plant-based index and a healthful plant-based index) were scored based on a composite sum of positive or negative values assigned to plant-based or animal food groups in the diet.

The investigators adjusted for days diagnosed until the first questionnaire was given, age at diagnosis, year diagnosed, total energy intake, CaPSURE clinical site, race, walking pace, smoking status, Gleason risk score at diagnosis, prostate-specific antigen (PSA) level at diagnosis, and primary treatment.

The researchers also enquired about various factors that could bias the assessments, including smoking status, walking pace, history of diabetes, family history of prostate cancer, household income, education level, height, body mass index, alcohol use, multivitamin use, calcium supplement use, and selenium supplement use.

These variables did not influence the results of analyses examining plant-based diets in relation to risk of prostate-cancer progression.

The rationale for assessing walking pace was that in past studies in this group, walking pace had been a significant predictor for progression, along with clinical factors such as age, stage, and grade.

Key Findings

Of the 2,038 people in the study, in 204 (10%) the disease progressed over a median of 7.4 years of observation.

Participants who reported diets that included the highest amounts of plants had a 52% lower risk of disease progression and a 53% lower risk of recurrence compared to those whose diets incorporated the lowest amounts of plants.

Associations did not vary by the participants’ age, walking pace, grade at diagnosis, or cancer stage at diagnosis.

Next Steps

The researchers plan to analyse plant-based diets in relation to prostate-cancer-specific mortality.

They will also examine plant-based dietary measures in relation to the prostate cancer-specific quality of life at 2, 5, and 10 years from diagnosis.

Source: ASCO