Does Eating Processed Meat Cause Cancer?

Check out this answer from Consensus:

The evidence from multiple systematic reviews and meta-analyses suggests that high consumption of processed meat is associated with an increased risk of several types of cancer, particularly colorectal, stomach, and possibly breast cancer. While the exact mechanisms remain to be fully elucidated, the formation of carcinogenic compounds during meat processing and cooking is a likely contributor. Therefore, it is advisable to limit the intake of processed meat to reduce cancer risk.

The relationship between processed meat consumption and cancer has been a topic of significant research and debate. Numerous studies have investigated the potential carcinogenic effects of processed meat, leading to varying conclusions. This article aims to synthesize the findings from multiple research papers to provide a comprehensive overview of whether eating processed meat causes cancer.

Evidence from Systematic Reviews and Meta-Analyses

Several systematic reviews and meta-analyses have been conducted to explore the association between processed meat consumption and cancer risk. A comprehensive meta-analysis of prospective studies found that high processed meat intake was significantly associated with increased risks of several types of cancer, including colorectal, colon, rectal, and lung cancers1. Another systematic review supported these findings, indicating that processed meat consumption is associated with higher risks of colorectal, esophageal, gastric, and bladder cancers6.

Specific Cancer Types and Processed Meat

Colorectal Cancer

The link between processed meat and colorectal cancer is one of the most well-documented. The International Agency for Research on Cancer (IARC) has classified processed meat as carcinogenic to humans, primarily based on evidence related to colorectal cancer2. A meta-analysis of observational studies confirmed a modest but significant association between processed meat intake and an increased risk of colorectal cancer10.

Breast Cancer

The relationship between processed meat consumption and breast cancer has also been explored. A study using data from the UK Biobank cohort found that high processed meat consumption was associated with an increased risk of breast cancer, particularly post-menopausal breast cancer5. However, another meta-analysis indicated that the association between processed meat and breast cancer is weak and not statistically significant in most models9.

Stomach Cancer

Processed meat consumption has been linked to an increased risk of stomach cancer. A meta-analysis of cohort and case-control studies found that higher processed meat intake was associated with a significantly increased risk of stomach cancer8. This association was consistent across different study designs and populations.

Other Cancers

Research has also investigated the impact of processed meat on other types of cancer, such as esophageal, pancreatic, and bladder cancers. A series of case-control studies in Italy found that high processed meat consumption was associated with increased risks of esophageal and pancreatic cancers, although no significant association was found for other digestive tract and laryngeal cancers3. Additionally, a review highlighted the potential role of processed meat in increasing the risk of bladder cancer, particularly due to the formation of carcinogens during high-temperature cooking4.

Mechanisms of Carcinogenesis

The carcinogenic potential of processed meat is thought to be due to several factors. These include the presence of nitrates and nitrites, which can form carcinogenic N-nitroso compounds, and the formation of heterocyclic amines and polycyclic aromatic hydrocarbons during high-temperature cooking4 7. These compounds can cause DNA damage and promote carcinogenesis.

 

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Does eating processed meat cause cancer?

Cornelie Nienaber-Rousseau has answered Near Certain

An expert from North-West University in Nutrition

Red (beef, veal, pork and lamb) and processed meat (that underwent salting, curing, smoking or ageing such as hams, hot dogs, bacon products and pre-packaged deli meats) intake have been consistently associated with increased cancer risk on a population wide level (see bullet points below for a summary).

•       Choi et al. (2013) summarized a total of 4 cohort studies and 23 case-control studies in their meta-analysis and concluded that a higher consumption of red meat was associated with a greater risk of esophageal cancer.
•       Larsson and colleagues (2006) summarized 6 prospective studies and 9 case-control studies and found that increased consumption of processed meat increased the risk of stomach cancer.
•       The scientific evidence that red and processed meat influences colorectal carcinogenesis was judged convincing in the 2007 in the World Cancer Research Fund/American Institute of Cancer Research report. Chan and co-workers in a more updated summary of prospective studies (2011) reported that red and processed meats intake was associated with increased colorectal, colon and rectal cancers. The also revealed that cancer risk increased approximately linearly with increasing intake of both red and processed meats up to 140 g/day, where after the curve approached a plateau.
•       Larsson and Wolk (2012) summarized prospective studies to determine whether red and processed meat consumption increased the risk of pancreatic cancer. They found that processed meat intake was positively associated with pancreatic cancer risk in both men and women whereas red meat consumption was only positively associated with increased risk in men.
•       In 2010 Alexander and co-workers summarized nine studies to determine the relationship between meat consumption and breast cancer risk and found that intake of red meat and processed meat did not appear to associate with increased risk.

There are several compounds in cooked fresh red meat or processed red meat that have carcinogenic potential (heterocyclic amines, polyaromatic hydrocarbons and the degradation product of nitrosamines i.e. methyl carbonium). Some individuals are more prone to developing cancer when consuming red and processed meats due to genetic factors such as carriers of the ‘rapid’ N-acetyltransferase 2 (NAT2) alleles, which have been shown to be associated with a faster metabolism of carcinogenic substrates such as heterocyclic amines (reviewed by Hunter in 2005). Research regarding increased susceptibility to cancer when eating red or processed meats are needed to individualize recommendations.

The preparation method of meat could also influence risk. Heterocyclic amines can be prevented by marinating the meat with herbs or anti-oxidant oils prior to cooking or grilling (Smith et al., 2008). Polyaromatic hydrocarbon formation can be lowered by allowing sufficient oxygen to reach the meat and by keeping the cooking temperature low (Sampaio et al., 2021). The forming of nitrosamines where nitrates (relatively high in pink meats such as ham, pork and bacon) are paired with amino acids can be reduced by anti-oxidants including vitamin C (in lemon juice) (Herrmann et al., 2015; De Mey et al., 2017). Because the cooking methods could influence the carcinogenic effects of red and processed meats, future research should collect detailed data considering not only quantity, but preparation methods. It is important to note that giving exact intake recommendations in terms of red or processed meat consumption is complicated for a disease such as cancer with a multifactorial etiology wherein other dietary intake factors, genetics and physical activity also play a role.

For comprehensive insights into the impact of consuming processed and red meats on cancer risk, with a recent update on lab-grown meat, visit the Nutrition Unveiled website at nutrition-unveiled.ghost.io. In the post “Q&A: How Does Consuming Meat Affect Cancer Risk?” I also delve into the various meat preparation methods in greater detail.

 

Does eating processed meat cause cancer?

Tim Crowe has answered Near Certain

An expert from Thinking Nutrition in Nutrition

People who eat a diet low in processed and red meat are less likely to develop bowel cancer. This link is nothing new and the 2015 International Agency for Research on Cancer (IARC) report investigating how likely red meat and processed meats are to cause cancer was a summary of the research to date. The IARC concluded that processed meat and also likely red meat are linked to causing colorectal cancer.

Yet even the highest-level committee members of the IARC were not saying that if you eat a sausage you are a candidate for cancer. What they were warning about was that if processed meats were a daily feature of your diet, your risk of bowel cancer would go up.

So what is it about red and processed meats that can make them carcinogenic? The answer isn’t certain, but several plausible mechanisms have been proposed.

The first culprit is the haemoglobin pigment that gives red meat its colour. Haemoglobin breaks down to a family of chemicals called N-nitroso compounds in the gut. These compounds can damage the cells that line the bowel, causing them to divide and replicate more.

A second candidate could be the actual cooking process of red meat itself, especially grilling or barbequing. The combination of high temperatures and charring of meat produces chemicals on the surface of the meat that may increase the risk of colon cancer. One simple way to reduce the formation of these compounds is to marinate meat first. Think of it as a protective layer on the meat, but with the added bonus of extra taste.

Yet another theory is that the high iron content of meat could be the culprit. Iron is important for our health, but too much of it can place a higher oxidative stress (a process not unlike ‘rusting’) on the body, and damage cells lining the large bowel.

While a sausage sandwich every now and then isn’t going to do you much harm, if you are eating a lot of processed and red meat then it could be a good idea to try to cut down. The World Cancer Research Fund recommends eating no more than 500 grams of cooked red meat per week. And if you eat processed meat, really keep that to a minimum. Chicken and fish make excellent alternatives to red meat. Or you could even consider having more vegetarian meals in your diet. Time to get on the #MeatFreeMonday trend.

 

Does eating processed meat cause cancer?

Gideon Meyerowitz-Katz has answered Likely

An expert from University of Wollongong in Epidemiology, Public Health, Diabetes

There is good evidence that eating processed meats is likely to increase the risk of bowel cancer. It is worth pointing out that, although the reported risk is 18%, this is a relative risk and therefore not that useful for individuals. The absolute risk increase in the rate of cancer from eating 2-3 rashers of bacon per day is about 0.2%, which means that for every 1,000 people who eat extra bacon, about 2 will develop bowel cancer who otherwise wouldn’t. At a population level, these risks are quite important, but for individuals it’s hard to say whether the risk of eating processed meat is particularly meaningful.

 

Does eating processed meat cause cancer?

Richard Hoffman has answered Likely

An expert from University of Hertfordshire in Nutrition

Bacon is a much-loved, comforting breakfast item – during the global pandemic, sales have surged in the US and the UK. But while bacon may be delicious, experts recommend people eat little or no processed meats because of their cancer risk. But while the cancer risk from processed foods is certainly something to think about, that doesn’t mean bacon should be totally off the menu. In fact, you might be able to lower some of the cancer risk from eating bacon depending on how you cook it.

Nitrites are perhaps the best-known cancer risk in bacon. Nitrites are used as a preservative, and are also converted in the stomach into N-nitroso compounds (NOCs), which can cause cancer.

Some bacon products are now advertised as “nitrite-free”. However, some of these products merely replace synthetic nitrite with a vegetable source, which is still converted into NOCs. These carcinogens also form when bacon is fried. Some processed meats don’t contain nitrites and aren’t cooked (such as parma ham), so they carry a lower cancer risk compared to bacon.

But avoiding nitrites will not eliminate all cancer risks from bacon. This is because frying also generates two other major groups of carcinogens. One of these is a group called heterocyclic amines (HCAs). Fried bacon contains more HCAs than any other cooked meat, and high levels of advanced glycation end products (AGEs) which are also linked to cancer.

Both HCAs and AGEs are produced by a chemical process called the Maillard reaction, which increases rapidly with heat. So your cancer risk could depend on how you cook your bacon. For instance, lightly browned bacon has only one-tenth the HCAs of well-cooked bacon. The Maillard reaction causes browning (thus producing carcinogens), so cooking methods where there’s little browning also usually result in fewer HCAs and AGEs. Hence microwaved bacon has far lower levels of AGEs than fried bacon.

Grilling/broiling bacon under a direct flame may also be unwise, as close contact with a naked flame generates very high temperatures that also cause drying on the surface of the bacon. Both of these factors increase HCA formation.

As flavour comes with frying, many bacon lovers will probably baulk at the idea of only lightly fried bacon. Fortunately, it may be possible to reduce carcinogen production without compromising taste. This is because flavour molecules are produced by a different part of the Maillard reaction to that generating HCAs and AGEs.

Foods rich in antioxidants are able to reduce harmful oxidising chemical reactions. This may suppress the part of the Maillard reaction that leads to HCAs and AGEs. Frying with a cooking oil rich in antioxidants – such as extra virgin olive oil – may lower cancer risk compared to frying in other cooking oils which are much lower in antioxidants.

Oesophageal cancer

However, some groups may be at higher risk compared to others from the cancer-causing carcinogens in bacon.

Research has found a strong association between eating processed meat and an increased risk of oesophageal cancer called oesophageal adenocarcinoma. The UK has the highest incidence in the world of this deadly type of cancer.

The main pre-cancerous state for oesophageal adenocarcinoma is a condition called Barrett’s oesophagus. About 1 million people in the UK have Barrett’s oesophagus and around 3-13% of these people will go on to develop oesophageal adenocarcinoma – an eleven-fold greater risk than the general population.

So people with Barrett’s oesophagus should be particularly wary of eating bacon. The link between oesophageal adenocarcinoma and bacon is inflammation, with compelling evidence showing inflammation drives Barrett’s oesophagus to cancer. For instance, people with an inflamed oesophagus (oesophagitis) have a four-fold increased risk of oesophageal adenocarcinoma compared with the general population. And for those already with Barrett’s oesophagus, oesophagitis increases the risk of developing oesophageal adenocarcinoma thirty-fold.

Diets high in inflammatory foods are associated with an increased risk of oesophageal adenocarcinoma. As AGEs found in bacon are potent inflammatory molecules linked to increased cancer risk, the exceptionally high levels of AGEs in bacon may pose a particular risk for oesophageal inflammation and oesophageal adenocarcinoma. However, no research has yet tested whether the inflammatory compounds in fried bacon make it more of a cancer risk than other processed meat.

Due to this lack of research, current UK guidelines for the management of Barrett’s oesophagus make no mention of diet. But given what we know more generally about the carcinogens in bacon causing cancer, it’s best to remain cautious.

Worryingly, only about 10% of people with Barrett’s oesophagus know they have it. The majority of people with undetected Barrett’s oesophagus will have developed it as a result of chronic acid reflux. So bacon lovers who are prone to acid reflux may want to avoid bacon while they seek out treatment.

Either way, a few simple steps can help lower cancer risk – such as gently frying bacon on a low heat, using extra virgin olive oil, or lower oven or grill temperatures and switching to non-fried, nitrite-free processed meats. Eating a healthy diet – such as the Mediterranean diet, which is particularly effective at lowering inflammation in the body – may also help reduce overall risk.

This answer is from my article in The Conversation

 

Does eating processed meat cause cancer?

Vinod Gopalan has answered Likely

An expert from Griffith University in Medicine, Molecular Biology, Gastroenterology, Cell Biology

According to own findings and from reviewing other quality literature, red/processed meat has a strong risk for carcinogenesis especially in the bowel. Our own studies have indicated that controlled dose dependent exposure of some of the chemical molecules from red/processed meat consumption increases normal bowel cell proliferation and activation of many cancer causing genes. This is in alignment with previous experimental studies. However, there are multiple factors which should be considered here. For example, hereditary predisposition, salting, other chemical additions during meat processing, fat/oil, alcohol, amount meat consumption and the use of vegetables during this consumption.