Monday, November 23, 2015

A Meaty Topic: Red Meat, Cancer Risk, and the Benefits of a Plant-Based Diet


By Yikyung Park, ScD

A recent report on red and processed meat and cancer risk, written by the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO), sent shockwaves worldwide. After reviewing existing evidence, the report concluded that processed meat consumption is a cause of cancer and red meat consumption is probably a cause of cancer, too. Although the adverse effect of meat on health has been known for quite a while, many people seemed to be surprised by the IARC report.

As a part of IARC’s Monographs Programme, 22 experts from 10 countries reviewed more than 800 different studies on cancer in humans and concluded that high consumption of red and processed meat is carcinogenic to human. Most convincing evidence came from studies on colorectal cancer. For every 100 grams per day of red meat consumption , colorectal cancer risk incased by 17 percent.  One hundred grams is equal to about 3.5 ounces of steak, or a piece of meat about the size of a deck of cards.  Every 50 grams per day of processed meat consumption (about 6 slices of bacon) also increased colorectal cancer risk by 18%.

Although these risks aren't large, they are still important.

Cutting back on red and processed meat offers those at increased risk of cancer (such as those with a family history of the disease or who have previously had cancer) a relatively simple option for helping to lower their risk.

More broadly, the meat/cancer link has huge public health implications simply because so many people eat meat, with consumption increasing worldwide. On average in the United States, people eat about 50–100 grams per day of red meat and some people eat more than 200 grams daily. According to the U.S. Department of Agriculture Commodity Consumption by Population data, in 2012, Americans consumed on average 163 grams of total meat daily, of which 92 grams was red meat and 54 grams was poultry. Red meat consumption was higher in men, younger people, and obese people.

Red meat refers to unprocessed animal meat such as beef, veal, pork, lamb, and goat. Processed meat refers to any meat (such as, beef, pork, chicken, turkey) that has been salted, cured, fermented, smoked, or processed to enhance flavor or improve preservation. Examples of processed meat are hot dogs, luncheon meat, ham, sausages, corned beef, beef jerky, and canned meat. When meat is cooked at high temperatures (e.g., grilling, barbecuing, and pan-frying), it produces heterocyclic amines (HAA) and polycyclic aromatic hydrocarbons (PHA), which are known to cause cancer in animals. Also, meat contains heme iron that increases formation of N-nitroso compounds (NOC), another cancer causing agents. Nitrate and nitrite that are added to processed meats during the processing also forms NOC.

Meat is a good source of protein and B vitamins, which are needed to maintain health, but also high in saturated fat and may contain potentially cancer-causing chemicals mentioned above. Numerous studies have showed that high consumption of red and processed meat was related to an increased risk of colorectal cancer, but also an increased risk of coronary heart disease, diabetes, and premature death.

Furthermore, people who eat high amounts of red and processed meat also tend to eat more high-fat foods, sweet desserts, and refined grains, but fewer fruits and vegetables. This kind of overall dietary pattern has also been linked to an increased risk of cancer as well as other chronic diseases. 

On the other hand, a Mediterranean type-diet that is high in fruit, vegetables, beans, and whole grains and low in consumption of red meat has many health benefits. 

This recent wave of media coverage on the risks of red and processed meat - while a bit overblown - did highlight the important role that a largely plant-based diet has in lowering cancer risk and improving overall health.  Cutting back on red and processed meat by choosing more poultry, fish, and legumes is one step you can take.  Choosing more fruits, vegetables and whole grains while cutting back on refined grains and unhealthy fats (like saturated and trans fats) are others.  

Making such changes isn't always easy but everyone can do it.  The key is to start small and build from there. Change just one thing at a time.  Try out "meatless Mondays."  Or add an extra vegetable to your dinners a few times a week.   When such changes become a habit, add on other healthy options.  

For additional healthy eating and lifestyle tips, see our series - 8IGHT WAYS to Prevent Cancer (website).



References

Bouvarda V et al. Carcinogenicity of consumption of red and processed meat. Lancet Oncology, 2015. Available online 29 October 2015

Micha R et al. Red and processed meat consumption and risk of incident coronary heart disease, stroke, and diabetes mellitus: a systematic review and meta-analysis. Circulation. 2010;121(21):2271-83.

Sinha R et al. Meat intake and mortality: a prospective study of over half a million people. Arch Intern Med. 2009;169(6):562-71.

Sofi F et al. Adherence to Mediterranean diet and health status: meta-analysis. BMJ. 2008;337:a1344.

USDA Economic Research Service. http://www.ers.usda.gov/data-products/commodity-consumption-by-population-characteristics.aspx

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