Some starchy foods may reduce cancer risk
Flinders University News
A type of starch found in bananas, potatoes, whole grains and beans could help offset the cancer-associated consequences of a high red meat diet, new research from Flinders University shows.
The study, which has just been published in Cancer Prevention Research, a journal of the American Association for Cancer Research, shows that red meat and resistant starch have opposite effects on colorectal cancer-promoting molecules.
“This finding supports the consumption of resistant starch as a means of reducing the risks associated with a high red meat diet,” lead author Dr Karen Humphreys, a Research Associate at the Flinders Center for Innovation in Cancer at Flinders University, said.
“Unlike most starches, resistant starch escapes digestion in the stomach and small intestine, and passes through to the colon (large bowel) where it has similar properties to fibre,” she said.
“Resistant starch is readily fermented by gut microbes to produce beneficial molecules called short-chain fatty acids, such as butyrate, which have opposite effects on cancer-promoting molecules.”
As part of the study, 23 healthy volunteers between the ages of 50 and 75 were divided into two groups and consumed a red meat diet or a red meat plus resistant starch diet for four weeks, and after a four-week break switched to the other diet for another four weeks.
After eating 300 grams of lean red meat every day for four weeks, study participants had a 30 per cent increase in the levels of certain cancer-promoting genetic molecules called miR-17-92 in their rectal tissue, as well as an associated increase in cell growth.
But when they consumed 40 grams of butyrated resistant starch every day along with red meat for four weeks, miR-17-92 levels decreased to baseline levels.
With global meat consumption on the rise, Dr Humphreys said the findings highlight the importance of resistance starch in the human diet.
“Total meat consumption in Australia, the US, Europe and the developed world has continued to increase from the 1960s – in some cases it has nearly doubled,” Dr Humphreys said.
“In light of this research, red meat-eaters should be making a conscious effort to get more resistant starch into their diets.
“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.”
The study was funded by the National Health and Medical Research Council, the CSIRO and the Flinders Medical Centre Foundation.