Plant-based diets are gaining traction for their health and environmental benefits. Research is exploring connections between lifestyle factors and prostate cancer to help patients improve their survivorship. This article examines the relationship between plant-based diets and prostate cancer, drawing on recent studies and expert insights.
What is a Plant-Based Diet?
A plant-based diet is built around a plate filled with mostly vegetables, fruits, whole grains, and beans. “Plant-based” foods are increasingly on the radar. You can grab a green juice at most chain coffee shops, a decent salad at airport restaurants, or even a meat-free veggie burger. And at many local grocery stores or farmers’ markets, you can purchase ingredients to cook a veggie-based meal.
Not all plant-based foods are equal - think chips and soda compared to a green salad. The study authors used a plant-based diet score to distinguish between the quality of the plant foods.
Potential Benefits of Plant-Based Diets
Research shows many benefits of a plant-based diet, especially for overall and heart health. The benefits of a plant based diet are well documented. Consider adopting a more plant based diet as an “insurance policy” against many common diseases, and which also may be associated with benefits for the prostate. For example, in looking across multiple studies, vegetarians were found to have a 9% lower risk of death overall, 29% lower risk of death from heart disease, and 18% lower risk of cancer vs. non-vegetarians.
Plant-based diets are associated with multiple health benefits and a favorable environmental impact. Healthful plant-based diets, including vegetables, fruits, nuts, legumes, and whole grains, are associated with numerous health benefits, including reductions in diabetes, cardiovascular disease, and overall mortality. The benefits of a plant-based diet on health may be due to direct effects of their healthy components (e.g., fiber, antioxidants), reductions in intake of animal products, and potential reductions in obesity.
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Plant-Based Diets and Prostate Cancer Risk
A plant-based diet may reduce the risk of developing or dying from prostate cancer. First, plants contain several cancer-fighting compounds, evidenced in their rainbow of colors. Previous studies have shown plant-eaters to develop prostate cancer at lower rates than meat-eaters.
Studies on Plant-Based Diets and Prostate Cancer
A team, including PCF-funded investigators Dr. Stacy Loeb and Dr. Stacey Kenfield, reviewed multiple studies to address this question. The studies asked participants about their diet, followed them for many years, and counted the number of prostate cancer cases and deaths from prostate cancer. There was some variation in the definition of the diet; generally, vegetarians/vegans were compared to non-vegetarians. Overall, the authors reported that a plant-based diet was linked to either a decreased risk of prostate cancer or it had no effect on risk.
Aligned with these findings, a study authored by Drs. Loeb and Kenfield, along with PCF-funded scientists Dr. Lorelei Mucci and Dr. June Chan, followed more than 47,000 health professionals over 28 years. Investigators computed three different dietary scores for each participant: overall plant-based, healthful plant-based, and unhealthful plant-based.
Key results included:
- Eating a more plant-based diet overall was linked to lower risk of fatal prostate cancer. Men with the highest plant-based diet score had a 19% lower risk of fatal prostate cancer vs. men with the lowest diet score.
- Eating a healthful plant-based diet was linked to a lower risk of being diagnosed with localized prostate cancer.
- Some effects of diet differed by age. For example, among men under age 65 at diagnosis, eating a more plant-based diet was linked to a 42% lower risk of advanced prostate cancer.
Potential Mechanisms
How might a plant-based diet be protective against some types of prostate cancer? The authors suggest a number of possible biological effects, such as greater consumption of antioxidant and anti-inflammatory compounds that are naturally present in fruits and vegetables. There are several possible mechanisms through which greater consumption of plant-based foods and lower consumption of animal-based foods may influence prostate cancer risk. These includes greater intake of antioxidants and anti-inflammatory components in fruits and vegetables and reducing potentially harmful exposures associated with animal-based foods, such as hormones and heterocyclic amines created during high-temperature cooking. Diets high in animal protein may increase insulin resistance and insulin levels, and milk and dairy increase levels of IGF1, which are associated with prostate cancer risk .
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Age as a Factor
It is noteworthy that the impact of plant-based dietary consumption with prostate cancer risk appeared to be differential by age. Previous studies have suggested the importance of exposures earlier in life with prostate cancer risk. For example, a large-pooled analysis showed that higher IGF1 levels were much more strongly associated with prostate cancer risk in men age <60 y (RR: 1.80; 95% CI: 1.34, 2.42) than in men age >70 y (RR: 1.20; 95% CI: 0.13, 1.38; P for heterogeneity = 0.051). Similarly, hyperinsulinemic and inflammatory dietary patterns (e.g., including some overlapping components such as red and processed meat) have been associated with a higher risk of aggressive prostate cancer among men age <65 y.
Plant-Based Diets and Outcomes for Prostate Cancer Patients
A plant-based diet may improve outcomes among patients with prostate cancer.
Clinical Trials and Studies
Clinical trials of plant-based diets have focused on two groups of men with prostate cancer: those with low-risk disease on active surveillance, and those with biochemical recurrence after initial treatment. For example, the Prostate Cancer Lifestyle Trial randomized 93 men with low-risk prostate cancer to a one-year intensive lifestyle program including a very low-fat vegan diet, regular exercise, stress management, and a support group. Patients in the control group received usual care. After one year, patients in the intervention group had significantly lower PSA levels vs. the control group. After two years, significantly fewer patients in the intervention group had gone on to have prostate cancer treatment vs. in the control group. Patients in the lifestyle intervention group also experienced other health benefits, such as reduced weight, lower cholesterol, and less perceived stress.
Trials of a plant-based diet (coupled with stress reduction) in patients with recurrent prostate cancer showed an increase in PSA doubling time, which may suggest less aggressive cancer. These studies were small, with short follow-up time. While these findings are promising, more research is needed.
Impact on Quality of Life
Led by researchers at NYU Grossman School of Medicine and the Harvard T.H. Chan School of Public Health, the analysis of more than 3,500 men with prostate cancer explored whether eating a more plant-based diet was associated with quality-of-life issues that often arise after treatment. Similarly, the results revealed up to 14 percent better scores for urinary health, with fewer instances of incontinence, obstruction, and irritation. Eating more healthy plant-based food was also associated with better bowel function, which.
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Among the findings, the researchers say, eating high amounts of any plant-based food was linked to better sexual health, urinary health, and vitality scores, regardless of demographic factors, lifestyle differences, or history of other medical issues, such as diabetes.
A Recent Cohort Study
These findings suggest that consuming a primarily plant-based diet may be associated with better prostate cancer-specific health outcomes among men with prostate cancer. This longitudinal observational cohort study included men with biopsy-proven nonmetastatic prostate cancer (stage ≤T3a) from the diet and lifestyle substudy within the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) enrolled at 43 urology practices across the US from 1999 to 2018.
Participants completed a comprehensive diet and lifestyle questionnaire (including a validated food frequency questionnaire [FFQ]) between 2004 and 2016. The primary outcome was prostate cancer progression (recurrence, secondary treatment, bone metastases, or prostate cancer-specific mortality). Among 2062 participants (median [IQR] age, 65.0 [59.0-70.0] years), 61 (3%) identified as African American, 3 (<1%) identified as American Indian or Alaska Native, 9 (<1%) identified as Asian or Pacific Islander, 15 (1%) identified as Latino, and 1959 (95%) identified as White.
During a median (IQR) follow-up of 6.5 (1.3-12.8) years after the FFQ, 190 progression events and 61 prostate cancer-specific mortality events were observed. Men scoring in the highest vs lowest quintile of PDI had a 47% lower risk of progression (HR, 0.53; 95% CI, 0.37-0.74; P for trend = .003). The hPDI was not associated with risk of progression overall. In this cohort study of 2062 men with prostate cancer, higher intake of plant foods after prostate cancer diagnosis was associated with lower risk of cancer progression.
Considerations and Caveats
Dr. Loeb cautions that the men assessed in the study were mostly White healthcare professionals.
Yet another problem is lack of consensus on what constitutes a plant-based diet. Definitions can range from extreme vegan, to semi-vegetarian, or primarily plant-based, where some meat consumption is allowed.
"What we really need in this area are more rigorously designed, well-controlled randomized clinical trials," Dr. Freedland says. "We need to sort out whether diet is really protective, or if vegetarians and vegans are simply more health-conscious in other ways. Are they exercising more? Do they have better access to health care? Do they live in places with better air quality?
Despite these limitations, Dr. Freedland described the evidence associating vegetarianism and lower prostate cancer risk as intriguing and encouraging. In the meantime, he advises that the best lifestyle strategy for reducing cancer risk overall is to avoid obesity.
Practical Implications and Recommendations
“Our findings offer hope for those looking for ways to improve their quality of life after undergoing surgery, radiation, and other common therapies for prostate cancer, which can cause significant side effects,” said study lead author and urologist Stacy Loeb, MD. “Adding more fruits and vegetables to their diet, while reducing meat and dairy, is a simple step that patients can take,” added Dr.
This study provides more evidence that for patients diagnosed with localized prostate cancer, choosing plant based foods rather than animal products may be associated with a lower risk of your prostate cancer getting worse or coming back. Patients with localized prostate cancer are actually more likely to die of heart attack or stroke, rather than of their prostate cancer.
This amounted to eating just one or two more servings per day of healthy foods, particularly vegetables, fruits and whole grains, while eating fewer animal products, like dairy and meat. “These results could guide people to make better, more healthful choices across their whole diet, rather than adding or removing select foods,” said Vivian N. “Progressing to advanced disease is one of many pivotal concerns among patients with prostate cancer, their family, caregivers and physicians,” she said. “Making small changes in one’s diet each day is beneficial,” said senior author Stacey A. Kenfield, ScD, a UCSF professor of urology and the Helen Diller Family Chair in Population Science for Urologic Cancer.
These findings suggest nutritional assessment and counseling may be recommended to patients with prostate cancer to help establish healthy dietary practices and support well-being and overall health. The American Cancer Society (ACS) recommends eating a more plant-based diet, exercising regularly, maintaining a healthy weight and avoiding alcohol. However, few cancer survivors fully adhere to these guidelines after their cancer diagnosis and treatment, suggesting the need for patient education to close the gap between ideal and actual practices.