Resistant Starch Lowers Red Meat-Related Colorectal Cancer Risk

Intake of resistant starch might help lower the risk of colorectal cancer that is linked to the consumption of high red meat diet, a new study reveals.

Resistant starch is a type of starch that passes down the small intestine without being digested. It rather turns into short-chain fatty acids by the intestinal bacteria. In a new finding, researchers at the University of Adelaide, Australia, found that red meat-eaters should consume a particular type of starch in order to lower the risk of colorectal cancer.

The researchers focused on 23 healthy volunteers - 17 males and 6 females (aged between 50-75 years).  The participants either consumed red meat or red meat along butyrated resistant starch diet for four weeks. After the four week-washout phase the subjects then switched to another type of diet for a four weeks.

"Good examples of natural sources of resistant starch include bananas that are still slightly green, cooked and cooled potatoes [such as potato salad], whole grains, beans, chickpeas, and lentils. Scientists have also been working to modify grains such as maize so they contain higher levels of resistant starch," said Karen J. Humphreys, PhD, a research associate at the Flinders Center for Innovation in Cancer at Flinders University in Adelaide, Australia.

According to the researchers, the total consumption of red meat has been on the rise since the 1960s in the USA, European Union as well as the developed world.

When the resistant starch that isn't broken passes through the colon, it displays properties similar to fiber. This resistant starch is readily fermented by the gut microbes to produce beneficial molecules called short-chain fatty acids like butyrate.

After consuming 300g of lean red meat per day for four weeks, the participants noticed a 30 percent rise in levels of certain genetic molecules called miR-17-92 in the rectal tissue and an associated rise in cell proliferation. A 40 g intake of butyrated resistant starch per day along with red meat for almost four weeks dropped the miR-17-92 levels to baseline level.

"Red meat and resistant starch have opposite effects on the colorectal cancer-promoting miRNAs, the miR-17-92 cluster," said Humphreys. "This finding supports consumption of resistant starch as a means of reducing the risk associated with a high red meat diet."

The finding was documented in Cancer Prevention Research, a journal of the American Association for Cancer Research.