http://www.aicr.org/site/News2?abbr=pr_&page=NewsArticle&id=20691&news_iv_ctrl=1102Most Authoritative Report on Colorectal Cancer and Diet Ever Conducted: Links with Meat, Fiber Confirmed
Elisa BanderaWASHINGTON, DC – 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.
"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 report, released today as part of WCRF/AICR's groundbreaking Continuous Update Project, has examined the links between colorectal cancer risk and diet, physical activity and weight, and updated the colorectal cancer findings of the charity's 2007 Expert Report.
A systematic review of the evidence was carried out by WCRF/AICR–funded scientists at Imperial College London, who added 263 new papers on colorectal cancer to the 749 that had been analyzed as part of the 2007 Report. An independent CUP Expert Panel then analyzed the totality of evidence and made new judgments.
Meat Link Remains Convincing
For red and processed meat, findings from 10 new cohort studies were added to the 14 included in the 2007 Report. The CUP Expert Panel concluded that 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.)
Evidence of Fiber's Protective Role Upgraded
Pie Chart of Preventable Colon CancerThe CUP Expert Panel also concluded that the evidence showing that foods containing dietary fiber reduce colorectal cancer risk has become stronger since the publication of the 2007 report. They considered the evidence sufficient to strengthen the conclusion that foods containing fiber are protective from "probable" to "convincing".
The analysis for fiber added seven more studies to the existing eight from the 2007 Report; the CUP Expert Panel noted that the evidence has become much more consistent.
This reaffirms AICR's recommendation for people to eat a plant–based diet, including foods containing fiber, such as whole grains, fruits, vegetables and beans.
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 affirmed 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.
"There has been a lot of debate over the last few years about the strength of evidence that red and processed meat increase risk of cancer. We hope our review can help give clarity to those people who are still confused about the strength of the evidence.
"On meat, the clear message that comes out of our report is that red and processed meat increase risk of colorectal cancer and that people who want to reduce their risk should consider cutting down the amount they eat."
CUP Expert Panel member Dr. Elisa Bandera added: "Many people feel confused about cancer prevention because it can seem like a new study is published every week that suggests something either causes or prevents cancer.
"But the CUP takes the latest scientific findings and adds them to the existing body of evidence in a systematic way that ensures our advice takes the latest research into account. This means people can be confident that AICR's recommendations represent the most up–to–date, evidence–based information on cancer prevention available."
Notes to Editors:
The CUP report on colorectal cancer contains the judgments of the WCRF/AICR Continuous Update Project Expert Panel. It is chaired by Dr. Alan Jackson of the University of Southampton and the other members are: Dr. Elisa Bandera of the Cancer Institute of New Jersey; Dr. Stephen Hursting of the University of Texas; Dr. David Hunter of Harvard University; Dr. Anne McTiernan of the Fred Hutchinson Cancer Research Center; Dr. Hilary J Powers of the University of Sheffield; Dr. Ricardo Uauy of Instituto de Nutricion y Tecnologia de los Alimentos in Chile and the London School of Hygiene and Tropical Medicine; and Dr. Steven H Zeisel of the University of North Carolina. Dr. Arthur Schatzkin, of the National Cancer Institute, served on the CUP Expert Panel until his death in 2010. Professor Elio Riboli of Imperial College London is a panel observer, Dr. John Milner of the National Cancer Institute is an advisor.
The CUP Expert Panel made judgments on the strength of the evidence following a systematic review of the evidence by a team of scientists at Imperial College London led by Dr Teresa Norat.
The CUP central database is a unique and valuable resource for researchers. Once WCRF/AICR updates the evidence on all cancers, the CUP database will be made accessible to the world's scientific community.
The full WCRF/AICR CUP Expert Panel report.
The timing of the CUP Expert Panel report's publication coincides with the publication in the journal PLoS One of the Imperial College team's systematic review of the evidence on red and processed meat and colorectal cancer.
Following an analysis of the Imperial College team's report, the CUP Expert Panel concluded that there is convincing evidence that red meat; processed meat; excess body fat; and abdominal fatness (fat carried around the waist) increase risk of colorectal cancer.
The CUP Expert Panel concluded there is convincing evidence that regular physical activity reduces risk of colorectal cancer. They also concluded that foods containing dietary fiber, such as fruits, vegetables, whole grains and beans, reduce risk of colorectal cancer. The panel also judged that garlic probably reduces risk of colorectal cancer.
The CUP Expert Panel concluded that there is convincing evidence that alcohol increases colorectal cancer risk in men. For women, it probably increases risk.
The CUP Expert Panel judged that milk probably reduces colorectal cancer risk, but AICR does not make a recommendation regarding dairy foods because the evidence for overall cancer risk remains unclear.
The evidence also shows that dietary supplements containing calcium probably reduce colorectal cancer risk, but when this finding is weighed against the totality of evidence on diet and cancer, AICR still recommends looking to whole foods to get the nutrients we need, instead of relying on supplements for cancer protection.
Red meat refers to beef, pork and lamb. If a person eats 3.5 ounces of red meat every day (24.5 ounces per week), their risk of colorectal cancer will be 17% higher than someone who eats no red meat. If they eat 7.0 ounces of red meat every day (49 ounces per week), their risk will be 34% higher, and so on. The evidence shows that there is very little increase in risk for people who keep their intake of red meat to less than 18 ounces per week
Processed meat is meat preserved by smoking, curing, salting, or by the addition of preservatives. Examples include ham, bacon, pastrami and salami, as well as hot dogs and sausages. If a person eats 3.5 ounces of processed meat every day (24.5 ounces per week), their risk of colorectal cancer will be 36% higher than someone who eats no processed meat. If they eat 7.0 ounces of processed meat every day (49 ounces per week), their risk will be 72% higher.
There are set criteria that the evidence must meet for the CUP Expert Panel to be judged "convincing." The evidence must be robust enough for it to be thought highly unlikely to be modified in the foreseeable future as new evidence accumulates. All the following are also generally required:
Evidence from more than one study type;
No substantial unexplained heterogeneity within or between study types or in different populations relating to the presence or absence of an association, or direction of effect;
Good quality studies to exclude with confidence the possibility that the observed association results from random or systematic error, including confounding, measurement error, and selection bias;
Presence of a plausible biological gradient ('dose response') in the association. Such a gradient need not be linear or even in the same direction across the different levels of exposure, so long as this can be explained plausibly;
Strong and plausible experimental evidence, either from human studies or relevant animal models, that typical human exposures can lead to relevant cancer outcomes.