- Does Red Meat Cause Cancer? Clearing Up the Controversy - February 4, 2023
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Red meat is undoubtably a great source of nutrients and is even viewed as a ‘superfood’ by many. Despite having clear nutritional advantages, dietary guidelines in many countries continue to discourage people from eating red meat.
The main concern that surrounding red meat is a potentially increased risk of cancer. In fact, the WHO has even labelled red meat as ‘probably carcinogenic to humans’. But does red meat cause cancer?
This topic has been the subject of numerous studies and has generated a lot of debate in the scientific community. This article aims to separate fact from fiction on the link between red meat and cancer, so that you can make informed decisions about whether you should include in your diet.
- Red meat is one of the most nutrient dense foods on the planet but is associated with cancer.
- Heme iron, NCOs and HCAs are compounds that may cause cancer in the human gut.
- Certain vegetables are able to stop damage from carcinogenic compounds.
- Epidemiology shows red meat alone increases cancer, but the risk is not present when >5 servings of fruit/vegetables are consumed.
- Red meat can be a nutritious part of a balanced diet but should not be consumed in the absence of fruit/vegetables.
Red meat: Benefits vs. Risks
Red meat is one of the richest sources of nutrients in the world. This was confirmed in a recent study conducted by Ty Beal et al. (2022) that deemed 6 of the 10 most nutrient dense foods come from mammalian animals.
Iron, vitamin B12, vitamin A and zinc are some of the most common nutrient deficiencies in the world, but they are all abundant in red meat. It’s estimated that 1 billion people worldwide suffer from protein deficiency, but the positive effects that protein can have on weight management and body composition are not disputed. Red meat is a dense source of protein and provides a large amount of all essential amino acids necessary for growth and repair.
The counter argument is that ‘red meat causes cancer’. This is an opinion that has been put forth since 2015 based on assessments made by 22 scientists from ten countries following a meeting at the International Agency for Research on Cancer (IARC) in Lyon, France.
The report looked at a total of 14 epidemiological studies of red meat and determined that 7 of them showed a positive association between red meat consumption and colorectal cancer. They noticed a dose response relationship between red meat and colorectal cancer risk; every 100g of red meat increases your risk by 17%.
These WHO recommendations have validated the guidelines of countries across the world recommending minimization of red meat. Nations such as the UK, USA, Australia and others all recommend limiting red meat in various amounts due to its association with cancer.
Why is red meat a cancer risk?
A number of research papers have proposed mechanisms linking certain natural and heat-induced compounds in red meat with increased cancer risk.
A 2011 meta-analysis that included over 566,000 participants showed a consistent but modest increase in the risk of colon cancer with high heme iron intake. Mechanistic studies have attributed this rise in cancer to oxidative stress and DNA damage. Genome instability and DNA mutations have also been labelled as a product of red-meat-induced oxidative stress that may lead to cancer.
Despite these potential pitfalls, heme iron is an essential nutrient that constitutes 95% of physical iron in the body and allows red blood cells to carry oxygen. Iron deficiency (anaemia) impacts around 500 million people worldwide and can lead to fatigue, cognitive impairment and eventual heart failure.
Heme iron is only found in animal foods and is especially high in red meat. It is absorbed at a much higher rate than non-heme iron, which is found predominantly in plant foods. Therefore, the heme iron found in red meat is viewed as essential to maintaining iron status around the world.
One way to gain the benefits of heme iron without the potential pitfalls is through the ingestion of antioxidant containing foods rich in vitamin A, vitamin C, vitamin E, polyphenols and other plant derived chemicals. Imam et al. (2017) theorises that humans have endogenous antioxidants that can neutralise oxidative stress, but eating plant-derived antioxidants may mitigate issues caused by high levels of heme iron intake.
This study raises the possibility of a balanced diet being the answer.
N-Nitroso Compounds (NCOs)
Red meat gets its colour thanks to the presence of myoglobin. This bright pigment has the ability to stimulate N-nitrosation in the gut and subsequent DNA damage to cells lining the colon wall.
It’s worth noting that the production of NCOs is expedited by in the presence of nitrites that are used to preserve processed meats. This is one of the reasons why processed meats show increased risk of cancer in comparison to unprocessed red meat. It’s also a reason why studies looking at ‘red and processed meat’ often paint red meat in a bad light.
Animal studies have shown that chlorophyll, the pigment found in green vegetables, may decrease the incidence of colon cancer by preventing the production of potentially harmful compounds found in red meat. Another positive for those eating a balanced diet.
Heterocyclic amines (HCAs)
Heterocyclic amines (HCAs) are carcinogenic compounds that are produced when cooking red meat at high temperatures. The charring of the meat causes a reaction between creatine, amino acids and sugar that produces these mutagenic compounds. 2-amino-3 and PAHs may also be produced when cooking at high heat for long periods and both have shown carcinogenic capability.
Incidentally, cruciferous vegetable consumption has been shown to reduce the negative effects of HCAs and other carcinogenic compounds in the gut. It appears that ordering your steak medium-rare with a side of broccoli is your best bet.
Red meat and cancer risk: What do the studies say?
A 2017 study by Etemadi et al. looking at 566,000 participants showed a 26% increased risk of all cause mortality from 9 different diseases based on highest vs. lowest red meat intake. Other studies have come to similar conclusions, with a 2012 study showing a 16% increased risk of cancer after controlling for confounding for diet, exercise, smoking and other variables.
Many of the epidemiological studies linking red meat to cancer have been widely criticised by members of the scientific community. ‘Healthy user bias’ is often an issue since many people tend to consume red meat in the form of hamburgers or lasagne, while going vegetarian is often a choice made by people with other healthy lifestyle habits.
Some of the strongest data available comes from prospective cohort study of 9,825 people called the ‘Tomorrow Project’. It split people into groups based on how much red meat they ate per week and how many servings of fruit and vegetables they consumed per day. The results showed that people eating more than 500g of red meat per week (highest) and less than 3 servings of fruit/vegetables per day (lowest) had a 44% increased risk of developing cancer.
However, the same study showed that people eating over 500g red meat per week (highest) and more than 5 servings of fruit and vegetables per day (highest) had a 25% decreased risk of cancer.
The study also looked at the incidence of cancer in people consuming red meat with fibre or whole-grains and found increased risk of cancer. Therefore, it concluded that vegetables have a protective effect against the potential carcinogenic compounds in red meat.
Does red meat cause cancer?
Red meat intake does cause cancer based on the totality of evidence. Mechanistic data exists showing how compounds in red meat can be carcinogenic and most large epidemiological studies show increased cancer risk of around 20%.
However, the data clearly show that fruit and vegetable intake has the ability to reduce the cancer risk posed by red meat. Studies show that cruciferous vegetables and chlorophyll in green vegetables are able to protect against cancer causing compounds.
20% increased cancer risk is moderate-low based on the number of confounding variables. Studies show that people eating red meat have a higher BMI and tend to consume less fruit, nuts and seeds. These variables are often difficult to adjust for and may skew some of the epidemiological data.
The importance of overall dietary quality is obvious. Red meat as part of a fast food meal will increase cancer risk, but when consumed as part of a balanced diet that includes fruits and vegetables then risk appears to be attenuates.
Based on this research recommendations should be made that individuals eating red meat should increase fruit and vegetable intake.
Red meat has a wide variety of nutrients and is an important source of protein for people around the world. Communities should be educated about the benefits of a balanced diet as opposed to the demonization of one food group.
- Aune, D., De Stefani, E., Ronco, A., Boffetta, P., Deneo-Pellegrini, H., Acosta, G., & Mendilaharsu, M. (2009). Fruits, vegetables and the risk of cancer: a multisite case-control study in Uruguay. Asian Pacific Journal of Cancer Prevention: APJCP, 10(3), 419–428. https://pubmed.ncbi.nlm.nih.gov/19640185/
- Bastide, N. M., Pierre, F. H. F., & Corpet, D. E. (2011). Heme Iron from Meat and Risk of Colorectal Cancer: A Meta-analysis and a Review of the Mechanisms Involved. Cancer Prevention Research, 4(2), 177–184. https://doi.org/10.1158/1940-6207.capr-10-0113
- Beal, T., & Ortenzi, F. (2022). Priority Micronutrient Density in Foods. Frontiers in Nutrition, 9. https://doi.org/10.3389/fnut.2022.806566
- Beck, K., Conlon, C., Kruger, R., & Coad, J. (2014). Dietary Determinants of and Possible Solutions to Iron Deficiency for Young Women Living in Industrialized Countries: A Review. Nutrients, 6(9), 3747–3776. https://doi.org/10.3390/nu6093747
- Bingham, S. A., Hughes, R., & Cross, A. J. (2002). Effect of White Versus Red Meat on Endogenous N-Nitrosation in the Human Colon and Further Evidence of a Dose Response. The Journal of Nutrition, 132(11), 3522S3525S. https://doi.org/10.1093/jn/132.11.3522s
- Bouvard, V., Loomis, D., Guyton, K. Z., Grosse, Y., Ghissassi, F. E., Benbrahim-Tallaa, L., Guha, N., Mattock, H., & Straif, K. (2015). Carcinogenicity of consumption of red and processed meat. The Lancet Oncology, 16(16), 1599–1600. https://doi.org/10.1016/s1470-2045(15)00444-1
- CKS is only available in the UK. (n.d.). NICE. https://cks.nice.org.uk/topics/anaemia-iron-deficiency/background-information/prevalence/#:~:text=Iron%20deficiency%20is%20the%20most
- de Vogel, J. (2004). Green vegetables, red meat and colon cancer: chlorophyll prevents the cytotoxic and hyperproliferative effects of haem in rat colon. Carcinogenesis, 26(2), 387–393. https://doi.org/10.1093/carcin/bgh331
- Etemadi, A., Sinha, R., Ward, M. H., Graubard, B. I., Inoue-Choi, M., Dawsey, S. M., & Abnet, C. C. (2017a). Mortality from different causes associated with meat, heme iron, nitrates, and nitrites in the NIH-AARP Diet and Health Study: population based cohort study. BMJ, j1957. https://doi.org/10.1136/bmj.j1957
- Etemadi, A., Sinha, R., Ward, M. H., Graubard, B. I., Inoue-Choi, M., Dawsey, S. M., & Abnet, C. C. (2017b). Mortality from different causes associated with meat, heme iron, nitrates, and nitrites in the NIH-AARP Diet and Health Study: population based cohort study. BMJ, j1957. https://doi.org/10.1136/bmj.j1957
- FAO predicts global shortage of protein-rich foods. (n.d.). Alliance for Science. Retrieved February 4, 2023, from https://allianceforscience.org/blog/2020/07/fao-predicts-global-shortage-of-protein-rich-foods/
- Fogelholm, M., Kanerva, N., & Männistö, S. (2015). Association between red and processed meat consumption and chronic diseases: the confounding role of other dietary factors. European Journal of Clinical Nutrition, 69(9), 1060–1065. https://doi.org/10.1038/ejcn.2015.63
- Imam, M., Zhang, S., Ma, J., Wang, H., & Wang, F. (2017). Antioxidants Mediate Both Iron Homeostasis and Oxidative Stress. Nutrients, 9(7), 671. https://doi.org/10.3390/nu9070671
- Kaluza, J., Wolk, A., & Larsson, S. C. (2013). Heme Iron Intake and Risk of Stroke. Stroke, 44(2), 334–339. https://doi.org/10.1161/strokeaha.112.679662
- Maximova, K., Khodayari Moez, E., Dabravolskaj, J., Ferdinands, A. R., Dinu, I., Lo Siou, G., Al Rajabi, A., & Veugelers, P. J. (2020a). Co-consumption of Vegetables and Fruit, Whole Grains, and Fiber Reduces the Cancer Risk of Red and Processed Meat in a Large Prospective Cohort of Adults from Alberta’s Tomorrow Project. Nutrients, 12(8), 2265. https://doi.org/10.3390/nu12082265
- Maximova, K., Khodayari Moez, E., Dabravolskaj, J., Ferdinands, A. R., Dinu, I., Lo Siou, G., Al Rajabi, A., & Veugelers, P. J. (2020b). Co-consumption of Vegetables and Fruit, Whole Grains, and Fiber Reduces the Cancer Risk of Red and Processed Meat in a Large Prospective Cohort of Adults from Alberta’s Tomorrow Project. Nutrients, 12(8), 2265. https://doi.org/10.3390/nu12082265
- Reuter, S., Gupta, S. C., Chaturvedi, M. M., & Aggarwal, B. B. (2010). Oxidative stress, inflammation, and cancer: How are they linked? Free Radical Biology & Medicine, 49(11), 1603–1616. https://doi.org/10.1016/j.freeradbiomed.2010.09.006
- Ritchie, H., & Roser, M. (2017, August). Micronutrient Deficiency. Our World in Data. https://ourworldindata.org/micronutrient-deficiency
- Silva, E. O. de A. (2009). Higher Red Meat Intake May Be a Marker of Risk, Not a Risk Factor Itself. Archives of Internal Medicine, 169(16), 1538. https://doi.org/10.1001/archinternmed.2009.278
- Sun, Q. (2012). Red Meat Consumption and Mortality. Archives of Internal Medicine, 172(7), 555. https://doi.org/10.1001/archinternmed.2011.2287
- Walters, D. G. (2004). Cruciferous vegetable consumption alters the metabolism of the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in humans. Carcinogenesis, 25(9), 1659–1669. https://doi.org/10.1093/carcin/bgh164
- Zheng, W., & Lee, S.-A. (2009a). Well-Done Meat Intake, Heterocyclic Amine Exposure, and Cancer Risk. Nutrition and Cancer, 61(4), 437–446. https://doi.org/10.1080/01635580802710741
- Zheng, W., & Lee, S.-A. (2009b). Well-Done Meat Intake, Heterocyclic Amine Exposure, and Cancer Risk. Nutrition and Cancer, 61(4), 437–446. https://doi.org/10.1080/01635580802710741