In fact, the results have been so compelling when it comes to lowering the risk of specifically upper gastrointestinal (GI) cancers that researchers are now looking to replicate them to ensure nothing is lost.
“We found that resistant starch reduced a range of cancers by more than 60 percent. The effect was most pronounced in the upper intestine,” says lead researcher and nutrition expert John Mathers of Newcastle University in the UK.
Upper gastrointestinal cancers include cancers of the esophagus, stomach, and pancreas.
One of the researchers, Tim Bishop, a genetic epidemiologist from the University of Leeds, adds: “The results are exciting, but the magnitude of the protective effect in the upper GI tract was unexpected, so further research is needed to replicate these findings.”
Resistant starch is a type of starch that passes through the small intestine and then ferments in the large intestine where it feeds beneficial gut bacteria. It can be purchased as a dietary supplement that resembles fiber, and is naturally present in a range of foods, including slightly green bananas, oats, cooked and refrigerated pasta, rice, peas and beans.
The double-blind trial was conducted between 1999 and 2005 and included a group of 918 people with a condition known as Lynch syndrome. Lynch syndrome is one of the most common genetic predispositions to cancer that we know of, with an estimated 1 in 300 people carrying the associated gene.
Those who have inherited the Lynch syndrome genes have a significantly increased risk of developing colorectal cancer, as well as cancer of the stomach, endometrium, ovary, pancreas, prostate, urinary tract, kidney, bile duct, small intestine, and brain cancer.
To see how they could reduce this risk, participants were randomly assigned to one of two groups, with 463 unknowingly given a daily dose of 30 grams of resistant starch in powdered form for two years — roughly the equivalent of eating completely immature food. Bananas daily.
Another 455 people with Lynch syndrome took a placebo daily that looked like starch powder but had no active ingredients.
The two groups were then followed up 10 years later. The results of this follow-up are what the researchers just published.
In the follow-up period, there were only 5 new cases of upper gastrointestinal (GI) cancers among the 463 subjects who consumed resistant starch. This compared with 21 cases of upper GI cancer among the 455 people in the placebo group – a very marked decrease.
“This is important because upper GI cancer is difficult to diagnose and often not detected early,” Mathers says.
However, there was one area where resistant starch didn’t make much of a difference – in the incidence of bowel cancer.
More work is needed to find out exactly what’s going on here, but the team has some ideas.
“We think that resistant starch may reduce the development of cancer by altering the bacterial metabolism of bile acids and reducing those types of bile acids that can damage our DNA and eventually cause cancer,” Mathers says.
“However, this needs further research.”
To be clear, this experiment was conducted on people with a genetic predisposition to developing cancer and does not necessarily apply to the general population. But there can be a lot to learn with a better understanding of how resistant starch can help protect against cancer.
The original trial was called the CAPP2 study, and the team is now doing a follow-up called CaPP3, involving more than 1,800 people with Lynch syndrome.
While it may sound alarming that the rate of colorectal cancer doesn’t seem to be affected by resistant starch, don’t worry, the study had good news on that front, too.
The original trial also looked at whether taking a daily aspirin could reduce the risk of cancer. In 2020, the team published results showing that aspirin reduces the risk of large bowel cancer in patients with Lynch syndrome by 50 percent.
“Patients with Lynch syndrome are at high risk because they are more likely to develop cancer, so the finding that aspirin can cut the risk of colon cancers and starch-resistant other cancers in half is critical,” says Newcastle University geneticist Sir John. Burns, who conducted the trial operation with Mathers.
“Based on our experience, Latifa [the UK’s National Institute for Health and Care Excellence] Now I recommend aspirin to people who are genetically at risk of developing cancer, and the benefits are clear – aspirin and resistant starch.
The search was published in Cancer prevention research.