Commentary by Dr. Aasma Shaukat
A few weeks ago the World Health Organization’s cancer agency, The International Agency for Research on Cancer (IARC), labeled processed meat a carcinogen and found that the risk of developing colorectal cancer is small but rises with the amount consumed. A group of 22 scientists from diverse disciplines, reviewed 800 studies that investigated possible links between a dozen types of cancer with the consumption of red meat or processed meat, in various countries and populations with diverse diets over the last 20 years. The panel included experts that study the chemicals that are produced in processed and cooked meats.
The WHO researchers defined processed meat as anything transformed to improve its flavor or preserve it, including sausages, beef jerky and anything smoked. They defined red meat to include beef, veal, pork, lamb, mutton, horse and goat. The report said grilling, pan-frying or other high-temperature methods of cooking red meat produce the highest amounts of chemicals suspected of causing cancer. It also found red meat was linked to colorectal, pancreatic and prostate cancer, but the link was not as strong. IARC experts concluded that 1.75 ounces of processed meat, or about two strips of bacon, or the amount of six thin slices of ham, eaten daily increases the risk of colorectal cancer by 18 percent. Exactly why processed meats can cause cancer is still unknown. Possible reasons include chemicals released when meat is cooked at high temperature, or when treated with the nitrite process.
The study spurred a media frenzy across the US, and has been a leading topic of discussion in my clinics, endoscopy rooms and break rooms. Meat producers and meat lovers are angry, vegetarians are feeling vindicated, and nutritional researchers are welcoming the most comprehensive pronouncement yet on the relation between our modern meat-eating lifestyles and cancer.
So before you throw out the bacon, and swear off meats, here’s some points to ponder, and to put the WHO findings in perspective:
The way the studies are designed and conducted renders them prone to many methodological limitations, such as confounding and various kinds of bias. In simple terms, it is difficult to separate out the effect of red meat from total calorie intake, alcohol consumption, high BMI and lack of other protective factors such as exercise and use of aspirin, i.e. a direct link cannot be established.
And while processed meat was classified at the same level of risk as cigarettes or asbestos, that doesn’t mean salami is as bad as cigarettes, only that there’s a confirmed link to cancer. And even then, the risk is small.
The cancer agency quoted research by the Global Burden of Disease Project suggesting that 34,000 cancer deaths per year worldwide are linked to diets heavy in processed meat. That compared with 1 million deaths a year linked to smoking, 600,000 a year to alcohol consumption and 200,000 a year to air pollution. Overall, the lifetime risk of developing colorectal cancer in the U.S. is about 1 in 20, or 5 percent, according to the cancer society. By the WHO’s calculations, having a cold-cut sandwich every day would raise that to around 6 percent. In comparison the risk of lung cancer is increased 500 fold by smoking 3 cigarettes per day.
The IARC acknowledged that for an individual, the risk of developing colorectal cancer because of their consumption of processed meat remains small, but this risk increases with the amount of meat consumed, and in view of the large number of people who consume processed meat, the global impact on cancer incidence is of public health importance. While U.S. rates of colon cancer have been declining, it is the No. 2 cancer for women worldwide and No. 3 for men. This is still very relevant from a public health point of view, as there are more than 30,000 new cases per year of colon cancer, but it should not be used for scaremongering. The agency made no specific dietary recommendations and said it did not have enough data to define how much processed meat is too dangerous
In the U.S., we have long counseled our patients against eating lots of red or processed meat — and not just because of the cancer danger but because of the heart risks from the saturated fat and sodium. The IARC report further strengthens our advice to patients and families. In this regard, the report should be seen as an important step in helping individuals make healthier dietary choices to reduce their risk of colorectal cancer in particular. We should also be reminding our patients that cancer is a complex disease not caused by single foods.
So the bottom line is to tell your patients they should not panic and strive for a well-balanced diet, with diversity in food groups, including poultry, fish, vegetables and fruits. The key word here is moderation.
And yes, you should still enjoy your hotdog at the ballpark.
Aasma Shaukat, MD, MPH, FACG
ACG Governor for Minnesota
Section Chief, GI Section, Minneapolis VA Health Care System