A supplement containing resistant starch derived from foods such as bananas reduced the risk of upper gastrointestinal (GI) tract cancers in patients with Lynch syndrome. 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 John Mathers, PhD, MBBS, 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,” Dr Mathers added.

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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,” Dr Mathers explained in a press release. “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.”

“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,” explained study author Sir John Burn, MD, professor of clinical genetics at Newcastle University and Newcastle Hospitals NHS Foundation Trust.

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,” Dr 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,” Dr 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 a placebo or 30 g resistant starch every day for up to 4 years.

The treatment phase was followed by a 10-year follow-up period, supplemented with national cancer registry data from England, Finland, and Wales for up to 20 years in 369 of the participants, the authors explained.

Overall, 463 patients with Lynch syndrome received the resistant starch supplement, and 455 received placebo. After up to 20 years of follow-up, there was no significant difference between the treatment groups for the incidence of colorectal cancer.

However, there was a significant difference in the incidence of upper GI cancers. Five 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

“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,” said study author Tim Bishop, PhD, professor of genetic epidemiology at the University of Leeds.

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


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/

This article originally appeared on Clinical Advisor