Colorectal cancer

"Colorectal cancer is one of the most preventable cancers," said Elisa Bandera, MD, PhD, who served on the World Cancer Research Fund/ American Institute for Cancer Research's Continuous Update Project (CUP) Expert Panel that authored the report. "AICR has estimated that about 45 percent of colorectal cancer cases could be prevented if we all ate more fiber-rich plant foods and less meat, drank less alcohol, moved more and stayed lean. That's over 64,000 cases in the US every year."

Q: What are the risk factors for colorectal cancer?

A: Based on the CUP and National Cancer Institute data, risk factors for colorectal cancer include

• Age: Risk increases dramatically after age 50 years; 90% of all colorectal cancer cases are diagnosed after this age. 
• Personal history of polyps or inflammatory bowel disease
• Family history of colorectal cancer
• Cigarette smoking
• Diet low in fiber
• Diet high in red meat and processed meat
• Lack of physical activity
• Substantial consumption of alcohol 
• Obesity, particularly excess fat around the midsection

Q: How much alcohol did the CUP report find increases the risk of colorectal cancer?

A: The CUP found that risk for colorectal cancer started increasing with less than one serving of alcohol daily. For every 10 grams of ethanol – a standard drink contains approximately 14 grams of ethanol – there was a 10 percent increased risk of colorectal cancer. 

Q: How does alcohol increase colorectal cancer risk?

A: The precise mechanisms are not clear but there are many possiblities. Metabolites of alcohol such as acetaldehyde can act as carcinogens. Alcohol also interacts with tobacco, leading to DNA mutations that are less efficiently repaired in the presence of alcohol. Alcohol may also function as a solvent, enabling carcinogenic molecules to move into cells. Also, high consumers of alcohol may have diets low in essential nutrients, making tissues susceptible to carcinogenesis. 

Q: How much fiber do I need to get protection from colorectal cancer?

A: The CUP analyses found that every 10 grams of dietary fiber eaten daily linked to a 12 percent decreased risk for men and an 8 percent decreased risk for women for colorectal cancer. 

Consuming the recommended amount of whole grains daily had an even stronger protective link. The report found that eating three servings of whole grains daily linked to a 21 percent decreased risk of colorectal cancer. 

The 2010 Dietary Guidelines for Americans recommend that women (ages 19 to 50) consume 25 grams of fiber daily and men in the same age group consume 38 grams daily. The Guidelines recommend that half of all grains consumed daily be whole grains, which for many Americans translates to about three servings.