Prostate cancer is one of the most common cancers in men over 60, and many men want to know whether diet can influence how the disease progresses. A major study published in JAMA Network Open followed more than 2,000 men with biopsy‑confirmed, non‑metastatic prostate cancer to see whether eating more plant‑based foods made a difference.

The findings were striking: men who ate the most plant‑based diets had a significantly lower risk of their cancer worsening over time.

What the researchers wanted to understand

The study examined whether men who consumed more plant‑based foods after a prostate cancer diagnosis had a lower risk of:

• disease progression
• developing metastatic disease
• prostate cancer–specific mortality

Researchers used two dietary scores:

• PDI (Plant‑Based Diet Index): overall plant‑based eating
• hPDI (Healthful Plant‑Based Diet Index): emphasizes whole grains, fruits, vegetables, nuts, legumes

Who was included in the study

The study followed 2,062 men with non‑metastatic prostate cancer.

• Median age: 65
• Median follow‑up: 6.5 years
• Participants completed detailed dietary questionnaires

What the study found

• Men who ate the most plant‑based diets had a 47% lower risk of prostate cancer progression.
  Compared with men who ate the least plant‑based diets:
  • Hazard Ratio: 0.53 (95% CI 0.37–0.74)
  • P for trend: .003
• Benefits were even stronger for men with higher‑grade disease.
  Among men with Gleason ≥7, those with the highest hPDI scores had a 55% lower risk of progression.
• No significant association with prostate cancer–specific mortality.
  Diet did not change mortality risk during the follow‑up period.

Even modest increases in plant‑based foods were linked with meaningful reductions in progression risk.

Why plant‑based diets may help

Plant‑based diets are rich in:

• antioxidants
• anti‑inflammatory compounds
• fiber
• healthy fats

These nutrients may help reduce inflammation, improve metabolic health, and support a healthier hormonal environment — all factors that may influence prostate cancer biology.

What this means for your daily life

The encouraging message from this study is that men don’t need to become fully vegetarian or vegan to see benefits. Even adding 1–2 extra servings of plant foods per day was associated with better outcomes.

Simple ways to shift toward a more plant‑forward diet:

• Add berries or fruit to breakfast
• Swap one meat‑based meal per day for a plant‑based option
• Use olive oil instead of butter
• Include nuts or legumes as snacks
• Choose whole grains like oats, quinoa, or brown rice

These small changes may help support prostate health over time.

Reference

The study is available here: Plant‑Based Diets and Disease Progression in Men With Prostate Cancer (JAMA Network Open, 2024)