If you are a meat-eater, you have probably heard the latest ‘beef’ with beef. According to the World Health Association (WHO), there is convincing evidence that eating processed meat, and potentially red meats, is associated with an increased risk of cancer.
Embroiled in controversy, the recent WHO report – developed by the International Agency for Research on Cancer (IARC) and published in The Lancet – generated much noise and confusion in the media. At the heart of the issue remains a question that the report leaves unanswered – just how bad for our health is red meat and processed meats?
How did the WHO come up with the report?
To produce the WHO report, 22 international scientific experts from 10 countries gathered at the IARC headquarters in Lyons, France. Their job was to analyze and weigh up the evidence on how likely it is that meat can cause cancer.
The group reviewed 800 epidemiologic studies and classified them by strength of evidence into carcinogenic classification groups. The classification didn’t take into account the level of risk that each study found, nor various other differences between the methods or outcomes of individual studies.
In other words, the categories do not tell us exactly how much meat you need to eat, or anything about the other variables that could play into your overall lifetime risk of developing cancer. The classification was found on the strength of evidence, not the degree of risk.
How was the meat – and the evidence – classified?
According to the IARC press release, the experts classified the ‘carcinogenicity’* of processed and red meat in the following groups, according to the strength of the evidence they analyzed:
Processed meat – meat that has been preserved by curing, smoking, or adding salt and preservatives to extend the shelf life and give the meat a distinctive taste. Bacon, canned meats, hot dogs, sausages, beef jerky and luncheon deli meats such as ham or turkey are processed meats.
The IARC report classified this as Group 1: ‘carcinogenic to humans’, meaning “based on sufficient evidence in humans that consumption of processed meat causes colorectal cancer.”
Red meat – refers to all types of mammalian muscle meat, such as beef, veal, pork, lamb, mutton, horse, and goat.
The IARC report classified this as Group 2A: ‘probably carcinogenic to humans’, meaning “based on limited evidence that the consumption of red meat causes cancer and strong mechanistic evidence supporting a carcinogenic effect.”
What does carcinogenic mean?
*A carcinogen is a substance that can lead to cancer. The report suggests that some types of meat contain these types of molecules and therefore put us at an increased risk of developing cancer.
So, what is my risk of cancer if I eat red or processed meat?
According to the report, there is sufficient evidence to suggest that some types of meat can lead to cancer; mostly colorectal, but pancreatic and prostate cancers were also associated.
The researchers concluded that if you eat 50 grams (less than 2 ounces, or, less than two slices of bacon) of processed meat a day, your chances of developing colorectal cancer are increased by 18%, relative to the group who is not eating 50g a day. However, this is a relative risk; not an absolute risk. There is a big difference.
Absolute and relative risk
According to Cancer Research UK, relative risk tells you how much more, or less, likely the disease is in one group compared to another. For example, if you say “One drink a day increases breast cancer by 5%.” This tells you that 5% is the relative risk of developing cancer in the group who is drinking one drink a day.
But crucially, the statement does not tell us anything about the overall likelihood of the disease happening to you at all. This is what’s known as the absolute risk – your risk of developing the disease over a time period, often your lifetime.
According to the American Cancer Society, the lifetime risk of developing colorectal cancer is 1 out of 20 or 5%.
If we take the 18% risk found by eating processed meat daily, by the 5% lifetime risk , our risk for colorectal cancer over our lifetime is now increased by 1% giving us a 6% lifetime or absolute risk.
Although the researchers determined that eating red meat was ‘probably carcinogenic’, the risk from eating 100 grams (3.5 ounces) of red meat was found to increase the risk of colorectal cancer about the same.
What the WHO report brings to light, is that we need to understand what the risks actually mean and what risks we are comfortable living with.
So, should we stop eating meat?
From a nutritionist point of view, I don’t think so. If we look at all the facts, cutting meat from our diets could mean we are missing out on their documented health benefits. Red meat strikes an impressive nutritional chord. As a source of protein, your body uses red meat to build and repair bones and muscle. It contains many important vitamins and minerals, including heme iron (more bioavailable than plant-based non-heme iron), creatinine, zinc, phosphorous, vitamin D, and the B-vitamins – niacin, thiamine, riboflavin and vitamin B12.
Red meat is also one of the best food sources of lipoic acid, a powerful antioxidant. Cutting it out could even put you at risk of other health conditions, such as vitamin B12 deficiency or iron deficiency anemia.
How much meat is safe to eat?
When asked by NPR, Dariush Mozaffairan, Dean of the School of Nutrition Science and Policy at Tufts University, Massachusetts, stated that, “there’s not enough evidence to give meat eaters a specific amount that is OK to consume.” Instead he recommended “no more than one to two servings per month of processed meats, and no more than one to two servings per week of unprocessed meat.
Rather than cutting out red meat, the evidence points towards cutting back our consumption of red meat and re-thinking our love-affair with processed meats. I know, you’re thinking, “But… bacon is great with everything!” But the evidence suggests that we do need to reshuffle the cards, and cut back on our carnivorous ways. Our health will thank us for it in the long term.