In addition to being National Nutrition Month, March is Colorectal Cancer Awareness Month.
According to the CDC, of cancers that affect both men and women, colorectal cancer is the
second leading cause of cancer-related deaths in the United States, with more than 50,000 people
succumbing to the disease each year.
Similar to mammograms for breast cancer screening, or getting your skin checked by your
dermatologist, colonoscopies are how doctors screen for colorectal cancer. A colonoscopy is a
procedure in which a doctor uses a scope and examines the colon for polyps, or little growths in
the lining of the colon that can be cancerous or pre-cancerous.
Colon Cancer Risks
- Age (over 50 years old)
- Race (African-Americans are at higher risk)
- Family or personal history of polyps or cancer
- Inflammatory GI conditions
- Previous radiation therapy to the abdomen
- Sedentary lifestyle
- Low-fiber, high-fat die
- Insulin resistance
- Heavy alcohol use
Diet and Colon Health
As dietitians, we know that fiber is good for the gut, and that many Americans get nowhere near
enough fiber in their diets. So, it might be beneficial to review the research and pack our dietitian
tool-belts full of evidence that might help convince our patients to opt for more fibrous foods.
A 2015 study published in the American Journal of Clinical Nutrition looked into two main
questions about the relationship between fiber and colon health. Their data came from the
Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, which included over 150,000
adults between the ages of 55-74 who had no history of these cancers. 1
At what point in the carcinogenic pathway does fiber act?
The researchers found that elevated dietary fiber intake, defined as at least 12.8 grams of fiber
per 1000 calories, was associated with a significantly reduced risk of incident distal colorectal
adenoma compared to individuals who ate less than 9.9 grams of fiber per 1000 calories.
However, this association was not observed in subjects with recurrent colorectal adenoma. These
results indicate that fiber may act early in the process of colorectal carcinogenesis.
Is all fiber equal?
We all know the differences between soluble and insoluble fiber, but fiber from food sources is
usually a combination of the two types. This study found that there was a greater reduction in
colorectal neoplasm risk with fiber consumption specifically from fruits and cereals (as opposed
to vegetables and legumes). Of course, it’s impossible to say that those results can be completely
accounted for by the fiber in those fruits and cereals, but these results are consistent with prior
What do I tell my patients?
There’s a lot more great evidence out there regarding the benefits of eating enough fiber, and
more recent research is showing us that we should be ensuring our patients are aiming to increase
their fiber intake both early and often. While it seems that fiber from grains and fruits may be
more impactful regarding colon cancer prevention, we can still promote the multitude of benefits
that come from eating plenty of fibrous veggies and legumes!
1) Kunzmann AT, Coleman HG, Huang W-Y, Kitahara CM, Cantwell MM, Berndt SI. Dietary fiber intake
and risk of colorectal cancer and incident and recurrent adenoma in the Prostate, Lung, Colorectal, and
Ovarian Cancer Screening Trial. The American Journal of Clinical Nutrition. 2015;102:881–90
2) Aune D, Chan DSM, Lau R, Vieira R, Greenwood DC, Kampman E, Norat T. Dietary fibre, whole grains,
and risk of colorectal cancer: systematic review and dose-response meta-analysis of prospective studies.
3) Ben Q, Sun Y, Chai R, Qian A, Xu B, Yuan Y. Dietary Fiber Intake Reduces Risk for Colorectal Adenoma:
A Meta-analysis. Gastroenterology. 2014;146.
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