by Dr. C.H. Weaver M.D,. updated 6/2021
According to the International Agency for Research on Cancer (IARC), eating processed meat products can increase a person’s risk for developing colorectal cancer. Processed meat is classified as meat that has been salted, cured, fermented, or smoked to add flavor or preserve the meat. These meats include ham, bacon, sausages, corned beef, hot dogs, canned meat, and beef jerky. Red meat includes beef, veal, pork, mutton, lamb, or goat.
Recent research suggests that the relationship between "red meat" and the risk of colon cancer is present with both processed and unprocessed meat.
According to the American Cancer Society, more than 102,000 individuals will be diagnosed with colon and 40,000 with rectal cancer annually in the United States. Combined colorectal (CRC) cancer is responsible for approximately 50,000 deaths each year. Most importantly however, CRC death rates have been declining over the past 15 years and death from CRC is very preventable.
The IARC report evaluated data from several studies conducted over the past 20 years and concluded that based on “sufficient evidence” processed meat causes CRC. They estimate that each 50-gram portion of processed meat eaten daily increases the risk of colorectal cancer by 18 percent.
Consumption of either red meat or processed meat increases an individual’s risk of developing CRC compared to those who eat little or no processed meat. Low meat intake is typically defined as no more than two servings per week. Whether or not to eliminate processed meat from your diet completely is an individual choice and probably not required. However reducing red meat consumption and substituting it with other alternatives like chicken and fish is likely to be beneficial.
The IARC report does not mean that everyone who eats processed or red meat will develop CRC, nor does it mean that not eating these meats will eliminate an individual’s risk of developing CRC. Under no circumstances does the report suggest that individuals who do not eat processed meat should forego screening for CRC with colonoscopy or other tests.
What is The Evidence That Meat Intake Linked is Linked With Cancer?
Doctors from Dana Farber Cancer Institute wanted to evaluate the link between environmental risk factors for colorectal cancer and the cancer driving mutations found in colorectal cancer so they examined the DNA sequencing data of 900 patients with colorectal cancer and found a previously undescribed pattern of mutations — a “mutational signature” — that exists in colorectal cancer.
They attributed the signature to alkylating damage and investigated the possible causes including red meat which is known to contain chemicals that potentially can cause alkylation. They found that patients who were consuming the most red meat overall, including both processed and unprocessed red meat, had cancers with increased alkylating damage.
They were surprised to learn that unprocessed red meat was associated with this pattern of mutations. Processed meat is a class 1 carcinogen, according to International Agency for Research on Cancer, but unprocessed red meat, which is currently labeled as probably carcinogenic, was also associated with alkylating damage.
Processed meat intake increased the risk of developing non-cardia gastric cancer, particularly in H. pylori-infected individuals.
Meat intake has been hypothesized to play a role in the development of gastric and esophageal cancers, but evidence for such a link is limited. To address this question within a large ongoing study, researchers evaluated information from the European Prospective Investigation Into Cancer and Nutrition (EPIC) study. This study enrolled a total of 521,457 study subjects from 10 European countries and found that
- Higher total meat intake, red meat intake, and processed meat intake were each linked with an increased risk of non-cardia gastric cancer.
- The link between meat intake and non-cardia gastric cancer was particularly strong for individuals infected with H. pylori.
- In spite of the increased risk with meat intake, relatively few individuals in this population developed gastric cancer.
- There was no strong evidence of a link between meat intake and gastric cardia cancer or esophageal adenocarcinoma.
The researchers conclude that higher total, red, or processed meat intake increased the risk of developing noncardia gastric cancer, particularly in H. pylori-infected individuals.
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Long-Term Consumption of Red Meat or Processed Meats Increases Risk of Colorectal Cancer.
According to a recent article published in the Journal of the American Medical Association, consumption of red meats and processed meats increases the risk of the development of colorectal cancer.
Researchers associated with the Cancer Prevention Study II (CPS II) Nutrition Cohort recently analyzed data regarding potential associations between the long-term intake of red meat or processed meats and the development of colorectal cancer. The study included nearly 150,000 individuals aged between 50 and 74 years residing in 21 different states. The individuals provided information regarding their meat-eating habits, as well as other dietary habits. The information was collected in 1982, as well as in 1992/1993, and follow-up was through August 2001. Overall, there were 1,667 cases of colorectal cancers diagnosed within the time of the study. Participants who ate the most red meat or processed meats had an approximately 50% greater chance of developing colorectal cancer than individuals who ate the least amount of the meat.
Further Evidence Indicates Red and Processed Meat Consumption Increases Risk of Colorectal Cancer
Results recently published in the Journal of the National Cancer Institute indicate that a high intake of red and processed meats increases the risk of colorectal cancer in men and women. These results were similar to evidence found in other studies.
The majority of research suggests that a high-fat diet that is low in fiber and folic acid may play a role in the development of colorectal cancer. However, recently published clinical studies have failed to produce evidence to support the theory that a diet low in fiber may cause colorectal cancer. Although, considerable evidence shows that a high intake of red meat increases the risk of colorectal cancer. In a previous study involving 76,402 women, researchers at the Harvard School of Public Health in Boston found that a “western” diet (higher levels of red and processed meats, sweets and desserts, French fries, and refined grains) increases the risk of colon cancer, compared to a “prudent” diet (higher intakes of fruits, vegetables, legumes, fish, poultry and whole grains). Once the data was adjusted for additional risk factors, it indicated that women on a Western diet were 46 percent more likely to develop colon cancer than women who ate a prudent diet.
Researchers associated with the American Cancer Society, Emory University and the National Cancer Institute have published previous evidence that prolonged high consumption of red and processed meat may increase the risk of cancer in the lower portion of the large intestine. Meat consumption was evaluated in over 148,000 adults who were between fifty and seventy-four years of age. Data was collected in 1982 and 1992 as part of the Cancer Prevention Study II (CPSII). Between 1992 and 2001 the investigators observed 1,667 cases of colorectal cancer. Overall, individuals with a high red meat and processed meat intake were 50 percent more likely to develop lower colorectal cancer than those with a low intake of red meat and processed meat. High meat intake was defined as at least three ounces per day for men and two ounces per day for women, and low meat intake allowed approximately two ounces or less of red meat no more than twice weekly for men and less than an ounce twice weekly for women. As well, high consumption of fish and poultry was associated with a lower risk of colorectal cancer.
The current study conducted by researchers in Europe involved 478,040 men and women between the ages of twenty-five and seventy, making it the largest study to date to evaluate the association of diet with colorectal cancer. Individuals were enrolled in this study between 1992 and 1998, and the mean follow-up was five years. Overall, the risk of developing colorectal cancer was 35 percent higher in persons eating the highest amount of red meat and processed food compared to those eating the lowest amount. The absolute risk of developing colorectal cancer within 10 years for those with the most red meat and processed meat consumption was 1.71 percent compared to a reduced 1.28 percent for those with the lowest consumption. Additionally, persons who consumed one portion of fish every other day compared to those who ate fish less than once per week, saw a risk reduction of 31 percent.
The researchers concluded that this large study provides “confirmatory” evidence that greater intake of red and processed meats increases the risk of developing colorectal cancer in both men and women. Individuals who have a high intake of these foods may wish to speak with their physician regarding screening for colorectal cancer.
Taken together research suggests that increased consumption of processed meet is associated with an increased risk of GI cancer and decreased consumption of red and processed meats could reduce the incidence of several types of cancer.
Cross A, Leitzmann M, Gail M, et al. A prospective study of red and processed meat intake in relation to cancer risk. Public Library of Science Medicine. 2007; 4: e325. DOI; 10.1371/journal.pmed.s0040325
Norat T, Bingam, Ferrari P, et al. Meat, fish, and colorectal cancer risk: The European Prospective Investigation into Cancer and Nutrition. Journal of the National Cancer Institute. 2005;97:906-916.
Fung T, Hu FB, Fuchs C, et al. Major dietary patterns and the risk of colorectal cancer in women. Archives of Internal Medicine. 2003; 163:309-314.
González CA, Jakszyn P, Pera G et al. Meat Intake and Risk of Stomach and Esophageal Adenocarcinoma Within the European Prospective Investigation Into Cancer and Nutrition (EPIC). Journal of the National Cancer Institute. 2006;98:345-54.