Are those steaks and hot dogs bad for you?
Several studies have found a connection between eating red and processed meat and colorectal cancer. But the reason for that connection hasn’t been clear.
To answer the question, researchers collected detailed information about the type of meat eaten by a large group of over 300,000 men and women and how the meat was cooked.
Linking that information to data on meat iron content, chemicals used in processing meat, and chemicals produced when meat is cooked at high temperatures, they were able to find that heme iron, nitrates and nitrites, and heterocyclic amines (HCAs) from high-temperature cooking increase risk for colon and rectal cancer.
Among 300,948 patients enrolled in a large, prospective trial, 2,719 developed colorectal cancer. When researchers ranked diets from those who ate the least red and processed meat to those who ate the most, they found:
- Heme iron was associated with a 13 percent increase in risk.
- Nitrates from processed meats increased risk by 16 percent.
- HCAs produced during high temperature cooking raised risk by 19 percent.
Generally, risks were higher for rectal cancer than for colon cancer, with the exception HCA proteins, which only increased colon cancer risk.
- Heme iron is available in the diet from meat, poultry and fish. Nonheme iron comes from plants, including lentils and beans. It is also added to enriched cereals, flour, and grain.
- Nitrates and nitrites are used to process meat into bacon, hot dogs, and sausage.
- HCAs are produced during high temperature cooking like grilling.
Amanda J. Cross and her associates concluded,
In conclusion, we found a positive association for red and processed meat intake and colorectal cancer; heme iron, nitrate/nitrite, and heterocyclic amines from meat may explain these associations.