If you prefer your bananas on the greener side, you might be getting more than just a slightly less sweet treat. Groundbreaking findings from a 20-year study suggest that a particular type of starch abundant in unripe bananas could significantly slash the risk of certain cancers, by over 60 percent.
This remarkable starch, known as resistant starch, isn’t exclusive to bananas. It’s also present in everyday foods like oats, cereals, pasta, rice, peas, and beans, making it a potentially accessible dietary component for cancer prevention.
This long-term research, spearheaded by experts from Newcastle and Leeds Universities, and published in Cancer Prevention Research, offers a beacon of hope, especially for cancers in the upper digestive system. These types of cancers are notoriously difficult to detect early, making preventative measures particularly valuable.
The study followed participants who consumed a daily dose of resistant starch, comparable to eating a slightly green banana.
The Power of Resistant Starch: Targeting Upper GI Cancers
Over the course of the study, around 1,000 individuals with Lynch syndrome participated. Lynch syndrome is a genetic condition that elevates cancer risk, particularly in the colon and rectum. These participants ingested the resistant starch supplement for roughly two years.
Interestingly, the study revealed that while resistant starch didn’t appear to impact bowel cancer rates, it had a profound protective effect against cancers elsewhere in the body. Specifically, it dramatically reduced the occurrence of cancers in the upper gastrointestinal (GI) tract by more than half.
This includes cancers of the esophagus, stomach (gastric cancer), biliary tract, pancreas, and duodenum. The impact of the resistant starch supplement was not short-lived; its protective benefits persisted for an impressive 10 years after participants stopped taking it.
Professor John Mathers, a human nutrition expert at Newcastle University, highlighted the significance of these findings: “We found that resistant starch reduces a range of cancers by over 60 percent. The effect was most obvious in the upper part of the gut.”
He further explained the dosage used in the study is easily achievable through diet: “The dose used in the trial is equivalent to eating a daily banana: before they become too ripe and soft, the starch in bananas resists breakdown and reaches the bowel where it can change the type of bacteria that live there.”
Resistant starch is readily available not only in foods but also as a powder supplement, and is naturally present in peas, beans, oats, and other starchy foods, Professor Mathers added.
How Resistant Starch Works: Feeding Good Gut Bacteria
Resistant starch stands out from other carbohydrates because it escapes digestion in the small intestine. Instead, it journeys to the large intestine where it undergoes fermentation, essentially acting as nourishment for beneficial gut bacteria.
We found that resistant starch reduces a range of cancers by over 60 per cent. The effect was most obvious in the upper part of the gut.
John Mathers
Professor of human nutrition, Newcastle University
Professor Mathers and his team propose a potential mechanism for this cancer risk reduction. They believe resistant starch may lower the levels of bile acids in the gut, substances known to cause DNA damage and potentially trigger cancer development. However, he emphasized that further research is essential to confirm this specific mechanism.
Professor Tim Bishop from Leeds’ School of Medicine echoed the need for continued investigation, stating, “The results are exciting but the magnitude of the protective effect in the upper GI tract was unexpected so further research is required to replicate these findings.”
It’s worth noting that earlier findings from the same study revealed that aspirin could cut the risk of large bowel cancer by 50 percent, indicating a multi-pronged approach to cancer prevention may be highly effective.
Long-Term Benefits Confirmed Over Two Decades
The study, conducted between 1999 and 2005, involved nearly 1,000 participants who were randomly assigned to receive either resistant starch in powder form or a placebo daily for two years.
Initially, at the end of the two-year treatment period, there was no discernible difference in overall cancer rates between the resistant starch and placebo groups. However, the researchers anticipated that the protective effects of resistant starch might take time to manifest, and strategically designed the study with a long-term follow-up period.
This foresight proved crucial. During the extended follow-up, a striking difference emerged: only five new cases of upper GI cancers were diagnosed among the 463 participants who had received resistant starch, compared to 21 cases among the 455 participants in the placebo group.
Professor Sir John Burn, from Newcastle University and Newcastle Hospitals NHS Foundation Trust, who co-led the trial, explained the study’s rationale: “When we started the studies over 20 years ago, we thought that people with a genetic predisposition to colon cancer could help us to test whether we could reduce the risk of cancer with either aspirin or resistant starch.”
He further emphasized the importance of these findings for high-risk individuals: “Patients with Lynch Syndrome are high risk as they are more likely to develop cancers so finding that aspirin can reduce the risk of large bowel cancers and resistant starch other cancers by half is vitally important”.
Professor Burn also highlighted the real-world impact of this research, noting that the UK’s National Institute for Health and Care Excellence (NICE) now recommends aspirin for individuals at high genetic risk of cancer, based partly on the evidence from this trial.
“The benefits are clear – aspirin and resistant starch work,” he concluded, underscoring the potential of these readily available interventions in significantly reducing cancer risk.
