Red meat and cancer

You may have noticed that there’s been a fair bit in the news lately about how eating lots of red and processed meat causes cancer. This latest media frenzy was caused after the International Agency for Research on Cancer (IARC) released a report in October stating that processed meat is a ‘definite’ cause of cancer, and red meat a ‘probable’ cause.

What are red and processed meats?
Red meat refers to all mammalian muscle meat, including, beef, veal, pork, lamb, mutton, horse, and goat. Note that this list includes pork, and minced meat would also come under this classification.
Processed meats include any meat that has been salted, cured, smoked or other processes used to enhance flavour or preserve. For example; bacon, salami, sausages, ham and canned meats.

What did the IARC report investigate?
Actually, this report didn’t investigate anything new, it was an evaluation of existing evidence and research. They evaluated over 800 studies that involved the relationship between intake of red and processed meats and cancer. According to this evidence, they then worked on grouping foods into certain classifications.
(An important thing to note is that the categories in the infogram below represent how confident the IARC are that something causes cancer, not how much cancer it causes).

151026-IARC-Meat-rating-TWITTER

Basically, what this chart is telling us, is that the IARC found sufficient evidence to conclude that high intakes of processed meats definitely cause cancer. The evidence for red meats was not as strong or clear, so is classified as a ‘probable’ cause of cancer.
Most of the evidence was linked to bowel (colorectal) cancer, and stems from a meta-analysis of 10 studies published in 2011. A key finding from this paper was that processed meat was more strongly linked to bowel cancer than red meat. They concluded that:
Every 50g/day of processed meat increases the risk of colorectal cancer by 18%.
Every 100g/day of red meat increases the risk of colorectal cancer by 17%.

However, this doesn’t mean that eating red or processed meats increases your risk of bowel cancer by 17/18%, as this is a measure of relative risk. In other words, someone who eats 50g of processed meat every day has a 1.18 times increased risk of developing bowel cancer when compared to someone who doesn’t eat processed meat. To put this into perspective, compare it with smoking (the most important avoidable cause of cancer in the world). Men who smoke 15-24 cigarettes a day have a 26 times higher risk of developing lung cancer than non-smokers.

So should I still eat red meat?
Red meat is fine in moderation, and is a valuable source nutrients including protein, iron and zinc. But, what exactly is moderation? This is much harder to quantify.
In general, the Department of Health recommends that people who eat more than 90g (cooked weight) of red meat per day should cut down to 70g or less. Try to keep processed meats such as sausages and salami as ‘occasional’ foods rather than things you eat every day. You could also try having alternative sources of protein such as chicken, turkey, fish, lentils and pulses (kidney beans, chickpeas etc.)

In conclusion, having a diet that is high in red meat is not good for you, but the occasional bacon sandwich is still fine. And importantly, the risks are much lower than other things associated with cancer risk, such as smoking.

More info:
IARC Press release
IARC FAQs

Cancer Research, UK: Processed meat and cancer
NHS Choices: Red meat and bowel cancer
Cancer Research, UK: Smoking and lung cancer

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