Plant-based diet demonstrates benefits along spectrum of prostate cancer

Loeb is a professor of urology and population health at New York University Grossman School of Medicine in New York, New York.

Stacy Loeb, MD, MSc

Although there are many nonmodifiable risk factors for prostate cancer, diet represents one of the most important modifiable factors along the spectrum of disease, from prevention all the way to advanced disease. Plant-based diets have become increasingly popular globally due to their many benefits for health and the environment. Our team became interested in looking at plant-based diets in prostate cancer because all the individual foods that are considered beneficial for prostate health are plant based (eg, tomatoes, cruciferous vegetables, soy, and nuts). By contrast, it is well known that meat and dairy products are associated with an increased risk of prostate cancer and disease progression. In fact, processed meat is considered a Group 1 carcinogen by the World Health Organization (the same category as asbestos, arsenic, and smoking!), whereas red meats such as pork, beef, and lamb are considered Group 2a carcinogens (the same category as lead and mustard gas!).

Can plant-based diets be useful in primary prevention of prostate cancer? By analyzing data from more than 47,000 participants in the Health Professionals Follow-up Study, we found that those who consumed more plant-based food had a 19% lower risk of fatal prostate cancer; the association was stronger for men younger than 65 years.¹ Other groups have found similar results. For example, data from the National Health and Nutrition Examination Survey showed that men who primarily consumed healthy, plant-based food were 53% less likely to have an elevated prostate-specific antigen (PSA) level.²

What about patients who already have prostate cancer—can a plant-based diet still be helpful? The answer is yes; consuming more plant-based food is also beneficial after diagnosis to reduce the risk of progression and side effects after treatment. For example, we conducted a systematic review of the literature on plant-based diets (eg, vegan or vegetarian) and prostate cancer.³ We identified 5 interventional studies conducted in patients diagnosed with prostate cancer that focused on 2 main clinical scenarios: (1) active surveillance and (2) biochemical recurrence after treatment. One study involving active surveillance was the Prostate Cancer Lifestyle Trial, a randomized clinical trial of patients who participated in a lifestyle intervention comprising a vegan diet, along with physical activity and mindfulness, compared with controls. The lifestyle intervention group was significantly less likely to progress to treatment. In addition, these participants experienced other health benefits from the lifestyle program, such as substantial reductions in cholesterol and weight. Other studies of patients with biochemical recurrence showed more favorable PSA kinetics (eg, longer doubling time) with plant-based diets.³

Can diet improve quality of life among men with prostate cancer? We recently presented exciting new data at the 2023American Society of Clinical Oncology meeting showing that increasing plant-based food consumption was associated with significantly better scores for sexual, urinary, and other quality-of-life domains (eg, bowel health and vitality) after prostate cancer treatment.⁴

Are there other reasons to care about nutrition in patients with prostate cancer? Patients with favorable-risk tumors have a much greater risk of death from cardiovascular disease compared with prostate cancer itself. Even among patients with metastatic prostate cancer, who are more likely to die from it, cardiovascular disease remains an important competing risk of morbidity and mortality. Healthy, plant-based diets have been shown to reduce the progression of major comorbid conditions such as coronary artery disease and diabetes.^5,6

It is important to note that nutrition is just 1 pillar of a holistic lifestyle medicine approach. Other key components include physical activity, stress management, avoidance of risky substances, restorative sleep, and social connections. Each of these has a beneficial impact for patients with prostate cancer, and they should all be routinely discussed with patients.

What are some resources on plant-based diets to share with patients? The Physicians Committee for Responsible Medicine (pcrm.org) and Nutrition Facts (nutritionfacts.org) have excellent websites with evidence-based videos, fact sheets, and recipes. There are also many helpful books (eg, How Not to Die) and documentaries (eg, The Game Changers, Forks Over Knives). Happy Cow is a website (https://www.happycow.net/) and app to find nearby sources of plant-based food using geolocation anywhere in the world. Finally, signing up for a challenge such as Meatless Mondays or Veganuary (going vegan for the month of January) can be a fun way to get started.

In summary, we have an important role as urologists in providing holistic care. Encouraging our patients to adopt a healthy, plant-based diet is a great way to simultaneously promote both prostate and overall health.

References

1. Loeb S, Fu BC, Bauer SR, et al. Association of plant-based diet index with prostate cancer risk. Am J Clin Nutr. 2022;115(3):662-670. doi:10.1093/ajcn/nqab365

2. Mouzannar A, Kuchakulla M, Blachman-Braun R, et al. Impact of plant-based diet on PSA level: data from the National Health and Nutrition Examination Survey. Urology. 2021;156:205-210. doi:10.1016/j.urology.2021.05.086

3. Gupta N, Patel HD, Taylor J, et al. Systematic review of the impact of a plant-based diet on prostate cancer incidence and outcomes. Prostate Cancer Prostatic Dis. 2022;25(3):444-452. doi:10.1038/s41391-022-00553-2

4. Loeb S, Hua Q, Bauer S, et al. Association of plant-based diet index with quality of life in patients with prostate cancer. J Clin Oncol. 2023;41(suppl 16):5037. doi:10.1200/JCO.2023.41.16_suppl.5037

5. Ornish D, Brown SE, Scherwitz LW, et al. Can lifestyle changes reverse coronary heart disease? The Lifestyle Heart Trial. Lancet. 1990;336(8708):129-133. doi:10.1016/0140-6736(90)91656-u

6. Rosenfeld RM, Kelly JH, Agarwal M, et al. Dietary interventions to treat type 2 diabetes in adults with a goal of remission: an expert consensus statement from the American College of Lifestyle Medicine. Am J Lifestyle Med. 2022;16(3):342-362. doi:10.1177/15598276221087624