A banana a day - or rather ensuring you have a regular dose of what's called "resistant starch" - can reduce the occurrence of certain forms of inherited cancer.
That's according to an international clinical trial led by eminent Newcastle medical figures. The trial - CAPP2 - involved almost 1,000 patients who have Lynch syndrome.
Lynch syndrome is a genetic condition which makes someone more susceptible to various forms of cancer. Bowel cancer is one of the major issues in people with Lynch, but cancers of the oesophagus, stomach and pancreas are also frequently seen. The CAPP2 trial has found that though resistant starch - found in foods such as oats, breakfast cereal, cooked and cooled pasta or rice, peas and beans and slightly green bananas - doesn't have an impact on bowel cancer rates, it does reduce the risk of many others..
The research was led by Prof Sir John Burn - who is a professor of clinical genetics at Newcastle Uni as well as chair of the Newcastle Hospitals NHS Trust - along with Newcastle Uni colleague Prof John Mathers and Prof Tim Bishop of the University of Leeds.
The study found that in patients with Lynch syndrome, a regular dose of resistant starch, reduced cancers in other parts of the body by more than half. The astonishing effect was seen to last for 10 years after stopping taking the supplement.
The research has now been published in Cancer Prevention Research - a prestigious journal. Previous research published as part of the same trial, revealed that aspirin reduced the risk of cancer of the large bowel by 50%.
Prof Mathers - who is a professor of human nutrition at Newcastle Uni - said: "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."
Resistant starch can be taken in supplement form, while in the trial the dose given to patients was equivalent to eating a daily banana before it becomes overripe. Prof Mathers added: "The starch in bananas resists breakdown and reaches the bowel where it can change the type of bacteria that live there.
"Resistant starch is a type of carbohydrate that isn’t digested in your small intestine, instead it ferments in your large intestine, feeding beneficial gut bacteria – it acts in effect, like dietary fibre in your digestive system. "
He said the team thought the starch helped reduce the build up of acids that can damage our DNA - but this will need further research to confirm. Prof Sir John Burn added: "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.
"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. Based on our trial, NICE now recommend Aspirin for people at high genetic risk of cancer, the benefits are clear – aspirin and resistant starch work."
The study first began more than 20 years ago in 1999 - then nearly 1,000 participants began either taking resistant starch supplements, aspirin, or a placebo. The study was designed to be follow-up long-term, and in this time there were just five new cases of upper GI cancers among the 463 participants who had taken the resistant starch compared with 21 among the 455 who were on the placebo.
Prof Bishop added: "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."
A further trial CaPP3 is now considering whether smaller doses of aspirin reduce cancer risk in a group of 1,800 people with Lynch.
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