A supplement containing resistant starch derived from foods such as bananas reduced upper gastrointestinal cancers by more than half. The effect lasted for 10 years after participants stopped taking the supplement, according to findings from a longitudinal study published in Cancer Prevention Research.

“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,” including esophageal, gastric, biliary tract, pancreatic, and duodenum cancers, explained lead study author Professor John Mathers, PhD, MBBS, BSc, director of Human Nutrition Research Centre at Newcastle University, UK. “This is important as cancers of the upper GI tract are difficult to diagnose and often are not caught early on,” Prof Mathers added.

Resistant starch is taken as a powder supplement and found in a wide range of foods such as oats, breakfast cereal, cooked and cooled pasta or rice, peas and beans, and slightly green bananas. It is a type of carbohydrate that is not digested in the small intestine. Instead, it ferments in the large intestine, feeding beneficial gut bacteria. “It acts in effect, like dietary fiber in your digestive system,” Prof Mathers said in a press release.

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Resistant starch has several health benefits and fewer calories than regular starch. “We think that resistant starch may reduce cancer development by changing the bacterial metabolism of bile acids and [reducing] those types of bile acids that can damage our DNA and eventually cause cancer. However, this needs further research,” Prof Mathers added.

Coauthor Professor Sir John Burn, MD, professor of clinical genetics at Newcastle University and Newcastle Hospitals NHS Foundation Trust, said: “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.” Previous research published as part of the same trial revealed that aspirin reduced cancer of the large bowel by 50%. “Based on our trial, NICE [The National Institute for Health and Care Excellence] now recommend aspirin for people at high genetic risk of cancer, the benefits are clear — aspirin and resistant starch work,” Prof Burn said.

“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,” Prof Mathers said.

Long-Term Study

The international trial, known as CAPP2, involved approximately 1000 patients with Lynch syndrome from around the world. Between 1999 and 2005, nearly 1000 participants were randomly assigned to take 30 g resistant starch every day for up to 4 years or a placebo. The treatment phase was followed by a 10-year follow-up period, supplemented with comprehensive national cancer registry data [from England, Finland, and Wales] for up to 20 years in 369 of the participants,” noted the authors.

Overall, 463 patients with Lynch syndrome received the resistant starch supplement and 455 received placebo. At the end of the treatment phase, no overall difference in the incidence of colorectal cancer was found in the study groups (Table). During the follow-up period, however, 5 new cases of upper GI cancers were found among the participants who had taken the resistant starch compared with 21 cases in the placebo group.

Table. Incidence of Colorectal Cancer and Upper GI Cancers in CAPP2 Study

CI, confidence interval

Professor Tim Bishop, PhD, MSc, BSc, professor of genetic epidemiology at the University of Leeds, who also ran the trial said: “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.”

The team is now leading the international trial CAPP3, with more than 1800 people with Lynch syndrome enrolled, to investigate whether smaller doses of aspirin can be used to reduce cancer risk.

The research was funded by Cancer Research UK, the European Commission, Medical Research Council, and the National Institute for Health Research.


Mathers JC, Elliott F, Macrae F, et al. Cancer prevention with resistant starch in lynch syndrome patients in the CAPP2 randomized placebo controlled trial: planned 10-year follow-upCancer Prevention Research. 2022;Jul 25;OF1-OF12. doi:10.1158/1940-6207.CAPR-22-0044

First trial to prove a diet supplement can prevent hereditary cancer. News release. New Castle University. July 25, 2022. Accessed July 26, 2022. https://www.ncl.ac.uk/press/articles/latest/2022/07/dietsupplementcanpreventhereditarycancer/