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Diet, lifestyle play ‘major role’ in colon cancer risk
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Global research has shown that eating whole grains and exercising reduce the risk for colorectal cancer, while eating red and processed meats, being overweight or obese, and drinking too much alcohol increase the risk, according to a new report by the American Institute for Cancer Research and the World Cancer Research Fund.
“Colorectal cancer is one of the most common cancers, yet this report demonstrates there is a lot people can do to dramatically lower their risk,” Edward L. Giovannucci, MD, ScD, an author of the report and professor of nutrition and epidemiology at the Harvard TH Chan School of Public Health, said in a press release. “The findings from this comprehensive report are robust and clear: Diet and lifestyle have a major role in colorectal cancer.”
As part of the Continuous Update Project (CUP), Giovannucci and other experts on an independent panel evaluated global research on the link between diet, weight and physical activity and colorectal cancer risk to update the previous 2011 CUP Colorectal Cancer Report. Overall, they assessed 99 studies including data on 29 million people, more than 247,000 of whom received a colorectal cancer (CRC) diagnosis.
Based on “strong evidence,” the panel determined that “convincing” causes of CRC included eating processed meat, drinking two or more alcoholic drinks (30 grams) per day, being overweight or obese, and being tall.
A dose-response meta-analysis also showed that every 50 grams of processed meat consumed per day increased CRC risk by 16% (RR = 1.16; 95% CI, 1.08–1.26).
They also concluded that physical activity “convincingly” reduces the risk for colon cancer but not rectal cancer, with studies showing a 20% significantly decreased risk when comparing the highest and lowest physical activity levels (RR = 0.8; 95% CI, 0.72–0.88).
Further, they found that eating whole grains, dietary fiber, and dairy, and taking calcium supplements “probably” reduces CRC risk, and high red meat intake (500 mg cooked per week) “probably” increases CRC risk.
A dose-response meta-analysis showed that every three servings, or 90 grams, of whole grains consumed per day cut CRC risk by 17% (RR = 0.83; 95% CI, 0.78-0.89).
Additionally, the report noted that “the evidence for red meat consistently showed a positive association in the dose-response meta-analyses in colorectal, colon and rectal cancer. The result was positive, but not significant, for colorectal and rectal cancers and significant for colon cancer.”
The AICR estimates that 47% of annual CRC cases in the U.S. could be prevented by lifestyle changes.
“Many of the ways to help prevent colorectal cancer are important for overall health,” Giovannucci said in the press release. “Factors such as maintaining a lean body weight, proper exercise, limiting red and processed meat and eating more whole grains and fiber would lower risk substantially. Moreover, limiting alcohol to at most two drinks per day and avoidance or cessation of smoking also lower risk.”
Smoking, as well as a diagnosis of inflammatory bowel disease, are both previously established risk factors for CRC, the report noted. Similarly, long-term aspirin use and hormone therapy in postmenopausal women are other established protective factors.
The report also included dietary factors linked to CRC by more limited “suggestive” evidence. The panel determined that eating fish and foods high in vitamin C, multivitamin supplements and vitamin D may reduce CRC risk, and low consumption of non-starchy vegetables and fruit (less than 100 grams per day) and eating foods that contain haem iron may increase CRC risk.
These emerging data highlight the impact eating a plant-based diet may have on cancer risk, according to Alice Bender, MS, RDN, AICR Director of Nutrition Programs.
“Replacing some of your refined grains with whole grains and eating mostly plant foods, such as fruits, vegetables and beans, will give you a diet packed with cancer-protective compounds and help you manage your weight, which is so important to lower risk,” Bender said in the press release. “When it comes to cancer there are no guarantees, but it’s clear now there are choices you can make and steps you can take to lower your risk of colorectal and other cancers.”
Considering their findings, the report’s panel of authors included several recommendations for general cancer prevention, including maintaining a healthy weight, exercising regularly and eating a healthy diet. They also recommended a healthy diet rather than relying on supplements for reducing cancer risk. – by Adam Leitenberger
Reference:
World Cancer Research Fund International/American Institute for Cancer Research. Continuous Update Project Report: Diet, Nutrition, Physical Activity and Colorectal Cancer. 2017. Accessed September 6, 2017. http://wcrf.org/colorectal-cancer-2017.
Disclosures: Healio Gastroenterology and Liver Disease was unable to confirm the authors’ relevant financial disclosures at the time of publication.