Major Report: Colorectal Cancer Risk Links to Diet, Activity and Weight
The most comprehensive and authoritative report on colorectal cancer risk ever published has concluded that red and processed meat increase risk of the disease and found that the evidence that foods containing fiber offer protection against colorectal cancer has become stronger.
The report, released last week as part of WCRF/AICR's groundbreaking Continuous Update Project, examined the links between colorectal cancer risk and diet, physical activity and weight. The report updated the colorectal cancer findings of AICR/WCRF's 2007 expert report.
"This report shows that 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."
The systematic review of the evidence was carried out by WCRF/AICR-funded scientists at Imperial College London. The scientists added 263 new papers on colorectal cancer to the 749 that were analyzed as part of the 2007 report. An independent CUP Expert Panel then analyzed the totality of evidence and made new judgments.
It's Convincing: Meat Increases and Fiber Decreases Risk
For red and processed meat, the CUP report concluded there is convincing evidence that both red and processed meat increase colorectal cancer risk.
AICR recommends that people limit consumption to 18 ounces (cooked weight) of red meat a week - roughly the equivalent of five or six small portions of beef, lamb or pork - and avoid processed meat. (The report showed that ounce for ounce, consuming processed meat increases risk twice as much as consuming red meat.)
For foods containing dietary fiber, the CUP Expert Panel concluded that the evidence showing it reduced colorectal cancer risk has strengthened since the 2007 report. The evidence was sufficient to strengthen the conclusion that foods containing fiber are protective from "probable" to "convincing."
"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."
Evidence on Activity, Body Weight, Alcohol Still Convincing
The experts concluded that studies published since 2007 added to the evidence that maintaining a healthy weight and being physically active are both convincingly linked to lowering colon cancer risk, while a healthy weight is linked to lower rectal cancer risk. The CUP Expert Panel also found that carrying excess fat - especially around the waist - is a convincing cause of colorectal cancer. There is also convincing evidence that alcohol consumption increases colorectal cancer risk in men and it also probably increases risk in women.
Dr. Alan Jackson, Chair of the WCRF/AICR CUP Expert Panel, said: "Our review has found strong evidence that many cases of colorectal cancer are not inevitable and that people can significantly reduce their risk by making changes to their diet and lifestyle.
"Because our judgments are based on more evidence than ever before, the public can be confident that this represents the best advice available on preventing colorectal cancer.
For the first time, Minneapolis claimed the top spot of America's healthiest and fittest city's, with Washington, DC – the previous leader – and Boston rounding out the top three, according to a new report of America's 50 most populous metro areas.
The American Fitness Index report, conducted by the American College of Sports Medicine, based their rankings on a series of health factors, including percent of residents who were physically active, smoking rates, obesity rates, percent of area that was parkland, and policies that supported physical activity. Data was collected from publically available federal government surveys, along with past studies.
Memphis, Louisville, and Oklahoma City ranked as among the least fit and healthy metro areas in the country. Out of 100 possible points, Minneapolis scored 77; Oklahoma City scored a 25.
CUP Research Features
Colon cancer is one of the most preventable cancers. AICR estimates that approximately 45 percent of colon cancers* – over 64,000 in the US – are preventable every year. How?
"Diet and activity matter." said AICR Registered Dietitian Alice Bender, MS RD. "We now know that by maintaining a healthy weight, being physically active and eating a healthy diet, we can dramatically reduce our risk of colorectal cancer."
Based on the new CUP colorectal cancer report, there are three general steps Americans can take to prevent colorectal cancer: Eat smart, move more, and stay lean.
- Aim to eat less than 18 oz. of cooked red meat weekly. Save processed meat for a few special occasions.
- Fill your plate with foods that contain fiber – whole grains, beans, vegetables and fruits. Minimally processed plant foods maintain their natural fiber.
- If you drink alcohol, women should consume no more than 1 standard drink daily, men no more than 2.
- Physical Activity
- Aim for at least 30 minutes of walking or other moderate activity daily; then step it up to 60 minutes.
- Find ways to incorporate movement into your day: break up screen time (computer, TV) with stretch breaks, hand weights workouts or jogging in place.
- Body fat
- Both excess body fat overall and abdominal fat are independently linked to increased colorectal cancer risk. Focus first on not gaining weight.
- For those who are overweight, work toward following a more plant-based diet that will fill you up with fewer calories: fill two-thirds (or more) of the plate with beans, whole grains, fruits and vegetables, with one-third (or less) of your plate meat, poultry, or fish.
Physical activity is crucial to getting to – and staying – a healthy weight. Begin by doing some form of physical activity every day, then work up to the 60 minutes recommended daily total.
* Estimates are based on AICR/WCRF 2009 report Policy and Action for Cancer Prevention.
Below, we have highlighted the most frequently asked questions related to the new WCRF/AICR CUP Colorectal Cancer report:
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.
Q: Do fiber supplements offer the same cancer protection?
A: The CUP found evidence for a protective effect with foods containing fiber; data came predominantly from dietary sources, not supplements, and therefore no effect can be attributed to supplements.
Q: Does abdominal fat independently increase the risk of colorectal cancer?
A: Yes. The CUP report found evidence that increasing waist circumference linked to increased risk of colorectal cancer. Abdominal fat that lies deep within the waist, surrounding the liver and other organs, is called visceral fat. Researchers are finding that visceral fat influences cancer risk, producing hormones such as insulin and other compounds linked to insulin resistance and chronic inflammation, which increase cancer risk. Belly fat also can effect sex hormones, such as increasing estrogen levels, which increase the risk breast cancer.
Q: Does physical activity influence risk of colon cancer only because it helps control weight?
A: No. Physical activity does play a role in controlling excess body fat, which is a cause of seven different cancers. But the evidence suggests that physical activity may also protect against colon cancer by decreasing inflammation, along with reducing insulin levels and insulin resistance.
The WCRF/AICR Continuous Update Project (CUP) is unique in that it is a living database, continuously updating the findings of the WCRF/AICR 2007 expert report. The goal is to ensure WCRF/AICR cancer prevention advice is always based on the latest research.
For the colorectal cancer update, WCRF/AICR-funded scientists at Imperial College London carried out the systematic review of the evidence according to a set protocol. The researchers added 263 new papers on colorectal cancer to the 749 analyzed as part of the 2007 report. The scientists assembled the relevant evidence and presented it to the WCRF/AICR CUP Expert Panel for discussion.
This independent CUP Expert Panel then analyzed the totality of evidence and graded the scientific evidence according to a strict set of predetermined criteria. The possible judgments are:
- "Limited, but Suggestive,"
- "Limited, with no Conclusion Possible" or
- "Substantial Effect on Risk Unlikely."
The experts on the panel synthesized and analyzed the entire body of evidence, forming judgments based on the set criteria.
The WCRF International website has published the Imperial team's full systematic literature review, and the WCRF/AICR CUP Expert Panel summary report.
Once WCRF/AICR updates the evidence on all cancers, the CUP database will be made accessible to the world's scientific community.
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