A new study found that eating a type of resistant starch can help reduce the risk of colorectal cancer associated with red meat consumption.
Studies from around the world have suggested that high consumption of meat is linked to an increased risk of colon cancer. In all cases the worry is confined to red meat. A new study by researchers from Flinders University in Adelaide found that eating a type of resistant starch can help reduce the risk of colorectal cancer associated with red meat consumption.
"Red meat and resistant starch have opposite effects on the colorectal cancer-promoting miRNAs, the miR-17-92 cluster," said Karen J. Humphreys, a research associate at the Flinders Center for Innovation in Cancer at Flinders University, in a press release. "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."
The study was conducted on 17 healthy males and six healthy females. All participants were aged between 50 and 75 years. They were put on a red meat or a red meat plus butyrate resistant starch diet for four weeks. After a four-week interval, the participants were made to switch diets. Researchers found that the participants that ate 300 g of lean meat daily for four weeks 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. However, those that ate 40 g of butyrate resistant starch per day along with red meat saw their miR-17-92 levels go down to baseline levels.
Resistant starch, unlike other starches, goes all the way through the small intestine without being digested at all. In this way, it is more like fiber, and in some cases is classified and labeled as fiber. Also, it is readily fermented by gut microbes to produce beneficial molecules called short-chain fatty acids, such as butyrate.
"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.
Scientists have offered a number of explanations for the link between red meat and colon cancer. One theory blames heterocyclic amines (HCAs), chemicals produced when meat is cooked at high temperatures. HCAs may play a role, but since high levels can also be present in cooked chicken, this is unlikely to be the whole explanation. Preservatives have also been implicated in the case of processed meats; nitrates are a particular worry, since the body converts them to nitrosamines, which are carcinogenic.
Scientists from England have offered another explanation. Their investigation recruited healthy volunteers. The volunteers ate one of three test diets for a period of 15 to 21 days. The first diet contained about 14 ounces of red meat a day, always prepared to minimize HCA formation. The second diet was strictly vegetarian, and the third contained large amounts of both red meat and dietary fiber. Stool specimens from the 21 volunteers who consumed the high-meat diet contained high levels of N-nitroso compounds (NOCs), which are potentially cancer-causing chemicals. The 12 volunteers who ate vegetarian food excreted low levels of NOCs, and the 13 who ate meat and high-fiber diets produced intermediate amounts.
A recent study also highlighted that consuming chilli peppers can reduce the risk of tumors associated with colorectal cancer. Colorectal cancer is a malignant tumor arising from the inner wall of the large intestine. It is the third leading cause of cancer in males and fourth in females in the U.S. Risk factors for this disease include heredity, colon polyps, and long-standing ulcerative colitis. Most colorectal cancers develop from polyps. Colon polyps and early cancer can have no symptoms. Therefore, regular screening is important.
The current study was published online in Cancer Prevention Research, a journal of the American Association for Cancer Research. The project was funded by the National Health and Medical Research Council of Australia, the Commonwealth Scientific and Industrial Research Organization (Preventative Health Flagship), and the Flinders Medical Center Foundation.
