Evidence suggests that red meat – beef, pork, lamb – can increase the risk of colorectal cancer if consumed in high enough proportions. A new study suggests, however that the consumption of resistant starch could potentially reduce this risk, making diets high in red meat safer to eat.
Although ever popular around barbecue season, red meat has been associated with increasing the risk of colorectal cancer more and more over the past 20 years. The authors of the study state that the popularity of red meat has been steadily growing since long before this association was made.
“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,” says Karen J. Humphreys, a research associate from Flinders University in Adelaide, Australia, who worked on the study.
The American Institute of Cancer Research state that red meat contains substances such as heme iron that have been linked to the development of colon cancer. Heme iron is the compound that gives red meat its color and can damage the lining of the colon.
The key to the study is the miR-17-92 cluster: colorectal cancer-promoting microRNAs that can be found within the rectal tissue. Levels of these microRNAs are increased by high consumption of red meat, and thus so too is the risk of colorectal cancer.
The study, published in Cancer Prevention Research, involved 23 healthy volunteers (17 male and six female) aged 50-75 trialing two different diets for 4-week periods; one diet was high in red meat consumption and one was high in resistant starch.
Resistant starch differs from other starches in that it escapes digestion while passing through the stomach and small intestine. When it reaches the large intestine, it is fermented by the microbes there, producing beneficial molecules known as short-chain fatty acids.
These short-chain fatty acids include butyrate, which is known to inhibit colonic tumor cells while promoting the growth of healthy colonic epithelial cells. The alternative diet to the red meat diet within the study was high in butyrate resistant starch.
The participants would embark upon eating one of the diets for a 4-week period, and then after a 4-week washout period, they would commence following the other diet for another 4 weeks.
The researchers found that after eating 300 g of lean red meat per day for 4 weeks, nearly twice the daily amount recommended by the American Heart Association (AHA), participants had a 30% increase in levels of miR-17-92 molecules in their rectal tissue.
After consuming 40 g of butyrate resistant starch per day alongside red meat for 4 weeks, the participants’ levels of miR-17-92 were brought back down to baseline levels.
Humphreys says the findings suggest that this could be a strategy for tackling the risks surrounding a diet involving high red meat consumption:
“Red meat and resistant starch have opposite effects on the colorectal cancer-promoting miRNAs, the miR-17-92 cluster. This finding supports consumption of resistant starch as a means of reducing the risk associated with a high red meat diet.”
Humphreys identifies the following as good examples of natural sources of resistant starch:
- Bananas (that are still slightly green)
- Whole grains.
Although over 90% of colorectal cancer cases occur in people who are 50 years old or more, this study is limited by the size and variety of its participating group. Further research will certainly need to expand upon its scale, as well as look out for other variable factors that could impact on the results.
As ever, maintaining a balanced diet is recommended as the best way to stay healthy and reduce the risk of illness.
The AHA recommend limiting the amount of red meat that is consumed every day, as it generally contains more cholesterol and saturated fats than other types of meat and vegetables. If red meat is to be consumed, it is best not to consume more than 170 g per day.
Previously, Medical News Today reported on a study that suggested red meat consumption could also increase the risk of developing breast cancer.