Does a high meat diet increase the risk of colorectal (cancer of the colon or rectum) cancer?

From the Guidelines

A high meat diet, particularly one rich in red and processed meats, increases the risk of colorectal cancer, and limiting red meat consumption to no more than 3 servings weekly and minimizing processed meat intake is recommended. The American Cancer Society guideline for diet and physical activity for cancer prevention 1 emphasizes the importance of a healthy eating pattern that limits or does not include red and processed meats. This is supported by the 2015 Dietary Guidelines Scientific Report, which concluded that dietary patterns rich in plant foods and lower in animal products and refined carbohydrates are associated with a lower risk of postmenopausal breast cancer, and plant-based patterns low in red and processed meat and added sugars are associated with a lower risk of colorectal cancer.

Several mechanisms explain the connection between a high meat diet and increased risk of colorectal cancer, including the production of carcinogenic compounds called heterocyclic amines and polycyclic aromatic hydrocarbons when red meat is cooked at high temperatures, and the presence of preservatives like nitrates and nitrites in processed meats that form potentially cancer-causing N-nitroso compounds in the body 1. The International Agency for Research on Cancer (IARC) working group determined that there is sufficient evidence supporting a procarcinogenic effect of processed meats on CRC, and consumption of red meat was determined to be “probably carcinogenic” based on limited evidence 1.

To reduce the risk of colorectal cancer, it is recommended to replace some meat meals with fish, poultry, or plant-based protein sources, and increase intake of fiber-rich foods like fruits, vegetables, and whole grains. A healthy eating pattern that includes a variety of vegetables, fruits, whole grains, and healthy protein sources can help achieve and maintain a healthy body weight and reduce the risk of chronic diseases, including colorectal cancer.

Key recommendations for reducing the risk of colorectal cancer include:

• Limiting red meat consumption to no more than 3 servings weekly
• Minimizing processed meat intake
• Replacing some meat meals with fish, poultry, or plant-based protein sources
• Increasing intake of fiber-rich foods like fruits, vegetables, and whole grains
• Maintaining a healthy weight and being physically active.

From the Research

Association Between High Meat Diet and Colorectal Cancer Risk

• A high meat diet, particularly one that includes large amounts of red and processed meat, has been associated with an increased risk of colorectal cancer 2, 3, 4, 5.
• The consumption of red meat has been shown to be positively associated with the risk of colorectal cancer, with a summary relative risk of 1.28 for the highest vs. the lowest intake categories 5.
• Processed meat consumption has also been linked to an increased risk of colorectal cancer, with a summary relative risk of 1.20 for the highest vs. the lowest intake categories 5.
• The evidence suggests that high intake of red and processed meat may increase the risk of cancer in the distal portion of the large intestine 4.
• A meta-analysis of prospective studies found that consumption of red meat and processed meat was positively associated with risk of both colon and rectal cancer, although the association with red meat appeared to be stronger for rectal cancer 5.

Mechanisms and Dietary Strategies

• Red meat contains high levels of haem iron, a molecule that can exert genotoxic and other adverse effects on the colonic epithelium, which may contribute to the increased risk of colorectal cancer 2.
• Dietary strategies that may help to contrast the harmful effects of haem iron include reducing red meat intake and consuming food containing antioxidant and chemoprotective substances 2.
• Adherence to a Mediterranean diet pattern, which is characterized by high consumption of fruits, vegetables, and whole grains, and low consumption of red and processed meat, may also reduce the risk of colorectal cancer 6.

Quantitative Associations

• The estimated summary relative risks were 1.28 for an increase of 120 g/day of red meat and 1.09 for an increase of 30 g/day of processed meat 5.
• Long-term consumption of poultry and fish was inversely associated with risk of both proximal and distal colon cancer 4.
• High consumption of red meat reported in 1992/1993 was associated with higher risk of rectal cancer, with a relative risk of 1.71 4.