Rice bran, navy beans boost gut microbiome, slow CRC cell growth
Higher dietary intake of rice bran and navy beans resulted in changes to the gut microbiome and reduced colorectal cancer cell growth in colorectal cancer survivors, according to the results of a randomized controlled trial presented at the American Association for Cancer Research Annual Meeting.
The results show promise for modulating the gut microbiota with these foods to control colonic inflammation and prevent CRC, the researchers concluded.
The American Institute for Cancer Research recommends increased dietary intake of whole grains and beans for CRC chemoprevention as these foods have been shown to inhibit colon carcinogenesis in animal and human epidemiological studies. Identifying an effective level of consumption of these foods, however, has been a challenge, but evidence suggests that “eating a half-cup of beans and 30 grams of rice bran per day is enough to see changes in small molecules that can confer protection against colorectal cancer,” according to Elizabeth P. Ryan, PhD, an investigator at the Colorado University Cancer Center and assistant professor at Colorado State University.
“The evidence is there in animals and we can now study this in people,” Ryan said in a press release. “The question is, what are we doing to achieve adequate levels of intake of these foods? It’s not enough to say ‘I eat them once in a while.’ That’s not going to work, particularly if you are at higher risk. You have to meet a dose, just like you need a dose of a certain drug, you need to reach intake levels and consume increased amounts of these foods, and that’s where people, including me, are challenged. Not everyone wants to open up a can of beans and eat them every day.”
To evaluate the chemopreventive effects of rice bran and navy bean intake, Ryan and colleagues performed a phase 2 pilot study (the BENEFIT trial), in which they randomly assigned 29 CRC survivors to consume 30 grams of rice bran per day, 35 grams of navy bean powder per day, or neither for 4 weeks.
They found that increased consumption of rice bran and navy beans led to higher dietary levels of fiber, iron, zinc, thiamin, niacin, vitamin B6, folate, and alpha-tocopherol. Further, stool microbiome analyses revealed the rice bran group had increased gut microbial richness and diversity, and the navy bean group showed increased gut microbial richness.
Notably, analysis of human stool metabolite extracts before and after the dietary intervention showed increased intake of rice bran or navy beans reduced growth of CRC cells.
These findings support the possibility of using rice bran or navy beans to modulate the metabolism from digestion, microbiota, and microbial biotransformation, and future studies of these foods should be conducted in a larger cohort and for a longer period to evaluate CRC control and prevention markers in colonic tissue, the investigators concluded.
Ryan and colleagues are currently performing additional studies of dietary modulation of human colonic inflammation for CRC chemoprevention.
“I really feel that there’s hope in this being a practical solution to improve gut health and specifically colorectal cancer prevention,” Ryan said in the press release. – by Adam Leitenberger
Borresen EC, et al. Abstract CT138/19. Presented at: AACR Annual Meeting; April 1-5, 2017; Washington, DC.
Disclosures: The researchers report no relevant financial disclosures.