Gut Check: The Microbiome and Prostate Cancer
What does gut health have to do with prostate cancer?
In this ASPI educational session, Michael A. Liss, MD, PhD, MAS, MBA, FACS, of the University of California, San Diego, discusses the microbiome and prostate cancer, with attention to what researchers are learning, what remains uncertain, and how this area may relate to men on Active Surveillance.
Dr. Liss explains what the microbiome is, how it is studied, and why diet and lifestyle are part of the conversation. He also discusses fermented foods, fiber, probiotics, commercial microbiome testing, antibiotics, biopsy-related infection concerns, and the challenges of studying microbes in the prostate itself.
Throughout the session, Dr. Liss is careful not to turn early microbiome science into simple instructions. He talks about promising areas of research, but also emphasizes that commercial tests, probiotics, supplements, and microbiome-related claims need to be understood in context.
This program is for educational purposes only and is not medical advice. Please speak with your own medical team before making decisions about diet, supplements, testing, biopsy approach, or prostate cancer care.
Presentation Slides
You can download Dr. Liss’ presentation slides here:
What You’ll Hear in This Video
Dr. Liss begins by explaining how he became interested in microbes through early research on how bacteria interact with the environment, and later through work on prostate biopsy infections and E. coli. From there, he connects microbiome research to prostate cancer, Active Surveillance, and lifestyle.
He describes the microbiome as almost another organ: something that helps digest food, creates metabolites, interacts with the immune system, and helps maintain the gut barrier. He also explains why the gut microbiome is easier to study than the prostate microbiome, where microbial DNA can be much harder to detect and interpret.
The talk includes practical discussion of diet, exercise, fiber, fermented foods, probiotics, alcohol, smoking, weight, and the limits of one-size-fits-all advice. Dr. Liss also discusses his own research looking at the gut microbiome as a possible lifestyle-related risk factor in prostate cancer, while making clear that this work is still being studied and validated.
Key Topics from the Q&A
- Why commercial microbiome tests may give different results
- Why Dr. Liss does not currently recommend a specific microbiome test for changing diet or clinical care
- How his research may relate to men on Active Surveillance, including some men with 3+4 disease
- What he said about probiotics after antibiotics and why he urges caution with generic probiotic claims
- Fermented foods such as kimchi, sauerkraut, kefir, and kombucha
- Questions about meat, carnivore diets, plant variety, oats, yogurt, berries, tomatoes, fish, and cruciferous vegetables
- GLP-1 medications, weight loss, and why microbiome effects are hard to isolate
- Artificial sweeteners, including monk fruit
- Antibiotics, rectal swabs, and transperineal vs. transrectal biopsy
- Where microbiome science may be heading, including precision nutrition, risk scores, stool testing, wearables, and future treatment tools
Video Chapters
0:30 Welcome, ASPI opening notes, and meeting guidance
5:29 Howard Wolinsky introduces the microbiome topic and Dr. Liss
10:06 Dr. Liss begins: disclosures and why he studies microbes
12:44 Talk roadmap and lifestyle as part of prostate cancer risk
14:29 What the microbiome is and how researchers study it
18:03 What the microbiome does: digestion, metabolites, immunity, and barrier defense
19:55 Possible ways the gut and prostate may interact
21:39 Feed, restore, select, and harness: Dr. Liss’s framework for microbiome research
22:33 Fiber, fermented foods, probiotics, and the MEAL Study
32:10 Dr. Liss’s gut microbiome research in prostate cancer
35:51 Q&A: commercial tests, Active Surveillance, GLP-1 medications, diet, probiotics, fermented foods, and the prostate microbiome
1:15:49 Q&A: biopsy antibiotics, rectal swabs, transperineal vs. transrectal biopsy, stool testing, wearables, and future tools
Related ASPI Resources
If this discussion raised questions about diet, lifestyle, Active Surveillance, or how to make sense of nutrition claims, these ASPI resources may be helpful:
- Diet and Nutritional Lifestyle — Dr. Stacy Loeb discusses diet and lifestyle questions for men with prostate cancer.
- Eat to Beat Prostate Disease — Dr. William Li discusses food, prostate health, lycopene, tomatoes, and why nutrition headlines need context.
- How Can Exercise Help Prostate Cancer Patients Like Me? — an ASPI program on exercise and prostate cancer.
- Short Video Library — brief clips from ASPI meetings, including videos on diet, exercise, lifestyle, PSA, MRI, biopsy, and more.
- Get Started with Active Surveillance — a starting point for men who are newly diagnosed or still learning the basics.
- Clinical Trial Finder — a guided way to explore clinical trials that may be relevant to Active Surveillance.