Should You Be Eating Red Meat & Is It ‘Bad’ For You?
Article by Dr Fiona Malcomson, BSC (HONS) MRES PHD
Red meat includes beef, pork, lamb and offal, as well as perhaps less commonly consumed meats such as venison and goat. Red meat has received a lot of bad press over the last years, particularly in relation to climate change and to health, such as bowel cancer risk.
Transitioning from a Paleolithic diet:
Our ancestors ate a Paleolithic diet, where they hunted free-roaming animals and ate relatively lean sources of meat. Nowadays, some of the meat products that we find in a supermarket are not as ‘natural’, and things like the diet and welfare of the animal can affect the quality of the meat. Some meats also undergo some type of processing, particularly processed meats such as bacon and types of sausages. This processing and packaging, as opposed to the red meat source itself, could be responsible for some of the detrimental effects on health.
Nutritional content of red meat:
Red meat is a great source of protein and a nutritious food containing vitamins, particularly B vitamins such as niacin, thiamine and riboflavin, and minerals such as zinc and phosphorus. Most red meat sources, such as beef, lamb and venison, contain more than 20g of protein per 100g (raw). Red meat is a complete source of protein. This means that it contains all nine amino acids that our bodies can’t make (essential amino acids) and that we need for our body to function well.
Red meat also provides vitamin D, mainly in offal such as liver, containing up to 1.5 micrograms per 100g serving. It contains a large proportion of iron, which is needed for metabolic function, oxygen transport and storage, and for immune function (for more information on iron, go to https://rhitrition.com/iron-why-is-it-important/ ). The type of iron in meat is haeme iron. Haeme iron is absorbed more easily (is more bioavailable) than non-haeme iron (found in plant foods), and makes up more than 95% of functional iron in our bodies.
Red meat and health:
Several studies and reviews have found that eating large amounts of red meat increases our risk of diseases such as type 2 diabetes (Neuenschwander et al 2019), heart disease and diverticular disease (Papier et al 2021), and also puts us at greater risk of death (including that from heart disease) (Abete et al 2014). Most of the evidence linking red meat and our risk of developing diseases is in relation to bowel cancer risk (discussed below). There’s also some evidence to suggest that red and processed meats increase the risk of other cancers including lung cancer, stomach cancer and pancreatic cancer (WCRF 2018). In contrast, lower intakes of red meat have been seen in people with anaemia. In a large study in almost 100,000 women in the US, those who ate more red meat had an 11% lower risk of having persistent anaemia (Thomson et al 2011).
Most of these studies are observational studies, meaning that we can observe associations but not draw conclusions on causation. The gold-standard study design to look at effects of nutritional, or other exposures, and health is an intervention study. Due to various reasons, including logistical and cost reasons, the number of these studies is smaller. It is also difficult, and potentially unethical, to run intervention studies that last long enough to look at disease incidence as an outcome, when diseases such as cancers can take decades to develop. In these cases, we tend to look at markers of disease risk. For example, blood lipids and blood pressure are risk markers for cardiovascular disease.
Red meat and bowel cancer risk
The World Cancer Research Fund (WCRF) have reviewed the existing evidence and concluded that this is strong for an increased risk of bowel (colorectal) cancer with higher consumption of red meat (WCRF 2018). In a recent study in the UK, in almost half a million participants, a 32% increase in bowel cancer risk was reported per 70 grams per day higher intake of red and processed meat (Knuppel et al 2020). In another large observational study conducted in the US, people who consumed the highest amounts of red meat were at 24% higher risk of colorectal cancer compared with those who ate the lowest amounts of red meat (Cross et al 2010). Other studies have not made the same observations, however, and have concluded that the type of red meat eaten is also important (Egeberg et al 2013).
Scientists have discovered several mechanisms through which red and processed meat can promote colorectal cancer development. For example, some of the products that form when we eat these meats, such as N-nitroso compounds, can cause damage to our large intestines by damaging our DNA. Processed meats tend to lead to greater production of these harmful products (discussed below). In fact, the International Agency for Research on Cancer (IARC) has classed processed meat as carcinogenic to humans (substances that can cause cancer) (Bouvard et al 2015).
As already mentioned, running intervention studies that feed participants red meat is tricky. One study in Australia fed healthy participants 300g of red meat every day for 4 weeks and found an increase in markers of bowel cancer risk, such as how much cells were growing in the large intestine and the formation of DNA adducts (which indicate damage to our DNA) (Humphreys et al 2014). It’s important to keep in mind that this study fed a very large amount of red meat! In the UK, adults consume on average just over 70g of red (including processed) meat, and 35g per day of unprocessed red meat (Hobbs-Grimmer et al 2021), which is a lot less than that given in the study.
Is it the red meat itself?
The cooking and processing of red meat are likely at least partly responsible for the effects of red meat on health. For example, some studies have reported links between processed red meat and heart disease, but not with unprocessed or fresh red meat (Micha et al 2010). Processed meats are those which are modified to improve preservation or flavour, for example by salting, curing or smoking. They include bacon, ham and pepperoni, as well as processed meats that do not come from red meat sources, such as processed chicken or turkey slices. This could be due to the high content of salt, preservatives and other additives in processed meat. High salt intake increases the risk of heart disease by increasing blood pressure, and preservatives such as sodium nitrate can also impact this.
In a systematic review and meta-analysis, which summarises the evidence from existing studies of specific quality and criteria, only processed meat - but not unprocessed ‘fresh’ red meat - intake was found to increase the risk of heart disease and of diabetes (Micha et al 2010). On the other hand, others have found that unprocessed red meat also increases the risk of heart disease as well as of death (all-cause mortality) (Zhong et al 2020).
Some meats are also high in saturated fat and cholesterol, which can increase our risk of heart disease and diabetes themselves, rather than the meat itself. The effects of red meat on disease risk are also affected by how we cook this. When meat is cooked on a high heat such as barbequing, more compounds such as polycyclic aromatic hydrocarbons and heterocyclic amines are made, which are carcinogens.
Take home message:
People may choose to eat or not to eat red meat for a variety of reasons, including cultural, ethical, religious, environmental and food preference, and we should always respect people’s dietary choices. Including red meat in our diet provides protein and a large proportion of haem iron, as well as other nutrients such as B vitamins. Whilst there are some associations between red meat and health-related outcomes, it can also be unhealthy to label foods as ‘good’ and ‘bad’ and eating a balanced diet is key for optimal health. It is likely that it is only high, frequent intakes of red meat that may have detrimental effects on our health.
There is strong evidence for an increase in our risk of developing bowel cancer with high intakes of red meat, and we are advised to eat no more than around 3 portions per week (500g per week or about 70g per day). The evidence for processed meats is stronger, and so limiting processed meat intake is also recommended.
Here are some tips on how to reduce red and processed meat intake:
• Try turkey or chicken mince when making dishes like a ‘Chilli con Carne’
• Swap half of the meat content (or even all) in dishes such as Bolognese or Cottage Pie with pulses or beans such as lentils
• Replace breakfast meats with other accompaniments to your eggs, such as avocado or grilled mushrooms or vegetarian/vegan sausages (or reduce the amount of sausages and bacon that you would normally have).
• Try plant-based meals e.g. Meat Free Mondays or pescatarian dishes e.g. Fish Fridays
• Experiment with different sandwich fillers
When choosing red meat, opt for lean cuts and unprocessed red meats such as lean mince or sirloin steaks, which are lower in fat, cholesterol and salt. When cooking red meat, try to avoid using high temperatures such as when grilling or barbecuing meat.
This blog post was written by Dr. Fiona Malcomson BSc (Hons) MRes PhD who is a Research Associate at Newcastle University with a PhD in Molecular Nutrition, and is also currently undertaking a Clinical Nutrition MSc at the University of Aberdeen. Fiona’s primary research interest is exploring the relationships between diet and other lifestyle factors and markers of large bowel health and of bowel cancer risk. Fiona has recently been awarded a grant by the WCRF to investigate relationships between adhering to the Cancer Prevention Recommendations and cancer risk and survival in the UK. Fiona is passionate about breaking down complicated science so it’s accessible for everyone and contributing to evidence-based nutritional and lifestyle public health recommendations through her research. You can find her on Instagram @Fiona.Malcomson and Twitter on @FionaMalcomson.
References:
Abete et al (2014) British Journal of Nutrition 112(5): 762-75
Bouvard et al (2015) The Lancet Oncology 16(16): 1599-1600
Cross et al (2010) Cancer Research 70(6); 2406–14
Egeberg et al (2013) Journal of Nutrition 143(4): 464-72
Hobbs-Grimmer et al (2021) European Journal of Nutrition https://doi.org/10.1007/s00394-021-02486-3
Humphreys et al (2014) Cancer Prevention Research 7(8):786-95
Knuppel et al (2020) International Journal of Epidemiology 49(5) 1540–1552
Micha et al (2010) Circulation 121(21):2271-2283
Neuenschwander et al (2019) BMJ 366:l2368
Papier et al (2021) BMC Medicine 19(1): 53
Thomson et al (2011) Journal of the American Dietetic Association 111(4):532-541
WCRF/AICR. Continuous Update Project Expert Report (2018) Diet, nutrition, physical activity and colorectal cancer. Available at dietandcancerreport.org
Zhong et al (2020) JAMA Internal Medicine 180(4):503-512