Eating green bananas can lower your risk of cancer by over 60%

Lynch syndrome is a hereditary condition that sharply raises the risk of several types of cancer. Caused by inherited mutations in DNA mismatch repair genes, it affects about one in 300 people. Those with the syndrome face up to an 80% chance of developing colorectal cancer during their lifetime, along with increased risks for endometrial, ovarian, and other cancers.

Preventing these cancers remains a critical challenge for healthcare providers. One hopeful strategy lies in simple changes to the diet—specifically, the use of resistant starch. This unique type of fiber, found in slightly green bananas, oats, and pulses, isn’t digested in the small intestine. Instead, it travels to the large bowel, where it ferments and feeds the gut’s helpful bacteria.

That fermentation process produces short-chain fatty acids, including butyrate, which scientists believe play a key role in suppressing tumor growth. Resistant starch may also shift how gut bacteria process bile acids, which can lead to fewer of the kinds that damage DNA and trigger cancer.

This potential cancer-fighting effect drew attention in the CAPP2 trial, a landmark study led by researchers at Newcastle and Leeds universities. Launched in 1999, the trial enrolled close to 1,000 people with Lynch syndrome, making it one of the largest studies of its kind.

Participants were randomly given one of three treatments: 600 milligrams of aspirin, 30 grams of resistant starch, or a placebo. They took these daily for two years in a double-blind design, meaning neither they nor the researchers knew who received what. The main focus was on preventing bowel cancer, though researchers also tracked other cancers linked to the syndrome.

Initial results seemed underwhelming. The data showed no major differences in cancer rates between the groups during the trial’s early years. But existing epidemiological evidence hinted that aspirin’s cancer-preventing effects might take longer to appear.

That insight led to an extended follow-up phase, supported by cancer registries in England, Wales, and Finland. Some participants were tracked for up to 20 years. This long-term data offered a surprising twist: while resistant starch didn’t lower bowel cancer rates, it cut the risk of other Lynch-related cancers by more than 50%.

The findings suggest resistant starch may offer protection against cancers outside the colon, possibly by creating a healthier gut environment over time. For people with Lynch syndrome—and those treating them—this humble dietary fiber may become a powerful tool in the fight against cancer.

The protective effects were particularly pronounced for upper gastrointestinal (GI) cancers, including esophageal, stomach, biliary tract, and pancreatic cancers.

Among 463 participants who consumed resistant starch, only five cases of upper GI cancers were reported, compared to 21 cases in the 455 participants who received the placebo. This reduction—over 60% for these hard-to-diagnose and often fatal cancers—marks a significant advancement in cancer prevention for Lynch syndrome patients.

Professor John Mathers, a nutrition expert from Newcastle University, emphasized the importance of these findings. “We found that resistant starch reduces a range of cancers by over 60%. The effect was most obvious in the upper part of the gut. This is important as cancers of the upper GI tract are difficult to diagnose and often are not caught early on,” he noted.

Mathers also highlighted the need for further research to understand the exact mechanisms, particularly the role of bile acid metabolism.

The trial also reaffirmed the benefits of aspirin. Participants who consumed aspirin experienced a 50% reduction in large bowel cancer risk. This evidence influenced the National Institute for Health and Care Excellence (NICE) to recommend aspirin for individuals at high genetic risk of colorectal cancer.

However, resistant starch’s protective effects extended beyond aspirin’s scope, covering a broader range of cancers and demonstrating persistent benefits even a decade after supplementation ceased.

Resistant starch’s versatility adds to its appeal. It can be incorporated into the diet naturally through foods like peas, beans, and whole grains or consumed as a powdered supplement. Beyond its cancer-preventive properties, resistant starch provides fewer calories than regular starch, making it a health-conscious choice.

The findings from CAPP2 also underscore the broader health benefits of dietary fiber. Past studies have linked high fiber intake with reduced risks of colorectal cancer, cardiometabolic diseases, and all-cause mortality.

Fiber’s protective role is attributed to its complex composition, which includes carbohydrates that resist small-bowel digestion and undergo fermentation in the large bowel. The production of short-chain fatty acids and alterations in gut microbiota are key mechanisms underpinning these health benefits.

Despite these promising results, the researchers remain cautious. Professor Tim Bishop from the University of Leeds expressed optimism tempered with a call for replication. “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,” he stated.

This caution has led to the launch of the CaPP3 international trial, involving over 1,800 individuals with Lynch syndrome. This study aims to determine whether lower doses of aspirin can provide similar protective effects while minimizing potential side effects. As the scientific community builds on these findings, resistant starch emerges as a simple yet powerful tool in cancer prevention.

Other benefits of resistant starch include the following, according to Johns Hopkins:

Funding for this groundbreaking research came from organizations including Cancer Research UK, the European Commission, the Medical Research Council, and the National Institute for Health Research. Their support underscores the global interest in addressing the unmet needs of Lynch syndrome patients and advancing cancer prevention strategies.

The implications of resistant starch extend beyond individuals with Lynch syndrome. Its potential as a cancer-preventive agent offers hope for broader populations, particularly those at high risk of upper GI cancers.

By integrating resistant starch into everyday diets, society can take a proactive step toward reducing the burden of cancer and improving public health outcomes.

Research findings are available online in the journal Cancer Prevention Research.

Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.

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