Consumption of a type of
starch that acts like fiber may help reduce colorectal cancer risk associated
with a high red meat diet, according to a study published in Cancer
Prevention Research, a journal of the American Association for Cancer
Research.
"Red meat and
resistant starch have opposite effects on the colorectal cancer-promoting
miRNAs, the miR-17-92 cluster," said Karen J. Humphreys, PhD, a research
associate at the Flinders Center for Innovation in Cancer at Flinders
University in Adelaide, Australia. "This finding supports consumption of
resistant starch as a means of reducing the risk associated with a high red
meat diet."
"Total meat
consumption in the USA, European Union, and the developed world has continued
to increase from the 1960s, and in some cases has nearly doubled," added
Humphreys.
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
fiber, Humphreys explained. Resistant starch is readily fermented by gut
microbes to produce beneficial molecules called short-chain fatty acids, such
as butyrate, she added.
"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
Humphreys.
After eating 300 g of
lean red meat per day for four weeks, study participants had a 30 percent
increase in the levels of certain genetic molecules called miR-17-92 in their
rectal tissue, and an associated increase in cell proliferation. Consuming 40 g
of butyrated resistant starch per day along with red meat for four weeks
brought miR-17-92 levels down to baseline levels.
The study involved 23 healthy
volunteers, 17 male and six female, ages 50 to 75. Participants either ate the
red meat diet or the red meat plus butyrated resistant starch diet for four
weeks, and after a four-week washout period switched to the other diet for
another four weeks.
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