Can I eat beef?

Recently the wife of a patient of mine asked “Can he eat beef?”  It transpires that the daughter and son-in-law have told the patient that he is not allowed to eat beef as it will make his cancer worst and beef causes cancer. I have been asked the same question by quite a number of patients. Is cancer caused by eating beef?

A recent study from the National Cancer Institute examined the associations between meat consumption (type of meat, cooking methods and related mutagens), heme iron, nitrite / nitrate and prostate cancer in 175,343 US men aged between 50 and 71 years of age (Am J Epidemiol 2009; 170: 1165 – 1177). These men were followed up for 9 years. The study showed that men who ate the most versus those who ate the least amount of red meat had a 12% higher risk of developing prostate cancer. For processed meat, the risk was 7%. The study also found that heme iron, barbequed/ grilled meat and benzo[a]pyrene were all associated with increased risk of prostate cancer. Nitrite and nitrate intakes were associated with increased risk of advanced prostate cancer.

In certain parts of China, the incidence of cancers of the oesophagus and stomach are much higher than the national average. Detailed studies finally showed that this was related to the pickled vegetables in their diet. The pickled vegetables contained significant amounts of nitrite and nitrate which are known to be carcinogenic. Recent studies have also shown that individuals who drink very hot tea have a higher incidence of cancer of the oesophagus. The likely mechanism here is related to the heat rather than the tea itself.

Cooking certain meats at high temperatures creates chemicals that are not present in uncooked meats. Heterocyclic amines (HCAs) are a group of chemical compounds formed from the cooking of muscle meats such as beef, pork, fowl and fish. HCAs form when amino acids (the building blocks of proteins) and creatine (a chemical in muscles) react at high temperatures during cooking. HCAs are potent compounds that can cause cells to mutate and in experimental animal models HCAs have been shown to induce tumours. Temperature is the most important factor in the formation of HCAs. Frying, barbecuing and broiling involve cooking at very high temperatures and thus produce the largest amounts of HCAs. Baking and oven roasting lead to lower levels of HCAs as the cooking temperature is lower. Poaching, stewing and boiling produce negligible amounts of HCAs. When meat is microwaved for 2 minutes before cooking, the HCA content is reduced by 90%.

From the examples given above, would it be correct to stop drinking tea because drinking hot tea has been shown to be associated with an increased risk of developing oesophageal cancer? Similarly, should one stop eating vegetables because pickled vegetables have been associated with increased risk of developing oesophageal and stomach cancers?

Association is not causation. Furthermore, the reasons behind an association may be due to factors other than the starting ingredient, such as beef. The reason for the association may be because of what you have done to the ingredient.