What Is Red Meat and Is It Bad for You?
Red meat is the muscle meat of mammals, such as cows, pigs, and goats. It is rich in iron-containing myoglobin, which gives it a distinctive dark red coloring. Commonly used types of red meat are beef, pork, veal, lamb, mutton, and goat.
Research finds high consumption of red meat to be correlated with an increased risk of colorectal cancer, type 2 diabetes, and cardiovascular and all-cause mortality.
Processed meat is usually, but not exclusively, made from red meat and has more significant adverse effects on health.
What Is Red Meat?
An accurate, complete definition of red meat is difficult to come across. Red meat is often defined as the muscle meat of mammals, rich in myoglobin, which becomes a red color when exposed to oxygen. Myoglobin is an iron-containing protein that holds oxygen in the muscle tissue.
All livestock is considered red meat. Livestock are domesticated farm animals, except for poultry.
Scientifically, dark red muscles are higher in myoglobin content and have a postural role with a slower contraction speed (slow twitch fibers) and a larger resistance to fatigue (1). In other words, well-trained muscles tend to be richer in myoglobin as these need more oxygen to function. Thus, chicken legs and thighs are darker, while chicken breast is pale pink. However, dark poultry meat is still classified as white meat.
Others describe red meat as the meat of four-legged mammals, whereas meat from fish and two-legged animals, such as poultry and rabbits, is considered white.
At the same time, some meat from two-legged animals can be classified as red meat from a culinary perspective. Duck meat, for example, is darker than chicken and is sometimes used as red meat in the kitchen. However, scientifically, duck meat is still white meat.
An exception to poultry meat being white is ratites. The USDA classifies these flightless birds, such as emu, ostrich, and rhea, as red meat because the pH of their flesh is similar to beef. The meat is dark red, and after cooking, it looks and tastes similar to beef (2).
The most popular red meat is beef. Others include pork, veal, lamb, mutton, goat, horse, donkey, buffalo meat, and other cattle and free-living animal meats.
Red Meat vs. Processed Meat
Meat is processed when it has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavor or improve preservation (3).
Most processed meat is made of red meat, particularly pork and beef. However, white meat can also be processed.
Mincing, freezing, cooking, and adding salt and pepper are not considered forms of processing. Sausages, ham, hot dogs, and corned beef are all examples of processed meats.
According to the study (4), processed meat can contain additional toxicants apart from heat toxicants that can be in red meat.
Processed meat has been studied to be more strongly associated with an increased risk of cancer incidence and is classified as a Group 1 carcinogenic. This means there is sufficient evidence to say that high consumption of processed meat causes colorectal cancer (5).
Is Red Meat Healthy?
The debate about red meat being healthy or not has been around for decades, and there is significant scientific data to support the discourse. Here, we will look at that data to summarize findings from research about how red meat affects health.
We’ve discussed how versatile the term “red meat” can be. Naturally, when talking about red meat, it is important to note that the impact depends on the type of red meat, the amount consumed, and the cooking method, among other things. However, research has not reached a definitive conclusion about which red meat and in which amounts is safest to consume.
High-temperature cooking methods, such as frying, grilling, or barbecuing, produce large amounts of carcinogenic chemicals in the meat, such as nitrosamines (NOC), heterocyclic aromatic amines (HAAs), and polycyclic aromatic hydrocarbons (PAHs). These chemicals are also pollutants found in tobacco, tobacco smoke, and the environment (5).
Therefore, well-done and pan-fried red meat may lead to a higher risk of cancer.
The increased saturated fat intake may be another one of the main factors of red meat leading to increased cardiovascular disease risk. Choosing lean red meats compared to fatty red meats can help decrease this risk (6).
One meta-analysis has found higher consumption of total red and processed meat to be associated with an increased risk of total cardiovascular and cancer mortality (7).
Another research concluded that there is a very small association between red and processed meat consumption and all-cause mortality and adverse cardiovascular outcomes (8). However, Harvard's T.H. Chan School of Public Health and Dr. Frank Hu, chair of the Department of Nutrition, have responded to this study by saying:
“This new red meat and processed meat recommendation was based on flawed methodology and a misinterpretation of nutritional evidence. An accumulated body of evidence shows a clear link between a high intake of red and processed meats and a higher risk for heart disease, cancer, diabetes, and premature death. The evidence is consistent across different studies (9).”
Red meat is classified as a Group 2A carcinogen, meaning limited evidence was found to support the association between high consumption and elevated risk of cancer. In simpler words, red meat probably leads to increased cancer risk.
Processed red meat is classified as a Group A carcinogen, with sufficient evidence to say that consumption of processed meat causes cancer.
Eating red meat is mainly correlated with colorectal or bowel cancer. Studies have also found red and processed meat to lead to a greater risk of stomach and pancreas cancer.
While some studies found a positive association, less evidence was found to conclude about the risk of red meat intake and lung, prostate, or breast cancer (5).
The cancer-causing effect of red meat has multiple possible mechanisms. There is moderate evidence that consumption of red and processed meat is capable of damaging DNA, leading to gene mutations that can cause cancer cells to form.
Processed meat intake also leads to oxidative stress in the cells, causing genetic mutations.
There is strong evidence that red meat promotes the growth of preneoplastic lesions in the colon. These are pathological tissues consisting of altered cells, which have a higher risk of becoming cancerous compared to healthy cells.
Heme iron contributes to the cancer-causing qualities of red meat.
Research has found an increased risk of ischemic heart disease with the consumption of unprocessed red and processed meat. The potential mechanisms may be increased saturated fat, sodium, and trimethylamine-N-oxide (TMAO) intake. TMAO is an organic compound produced by gut bacteria from animal products, which can promote atherosclerosis (10).
Meta-analysis has concluded that red meat intake has no differential effects on total cholesterol, low-density and high-density cholesterol levels, and blood pressure (10, 11). However, substituting red meat with high-quality plant products leads to a more favorable result in cardiovascular health (12).
Type 2 Diabetes
Unprocessed red and processed meats have also been associated with an increased risk of developing type 2 diabetes and metabolic syndrome (13, 14, 15).
Some of the potential mechanisms for this correlation include the high content of saturated fats and branched-chain amino acids leading to insulin resistance and heme iron, likely causing oxidative stress and pancreatic cell damage (13).
These findings are more prevalent in US-based studies and less apparent in Asian-based studies, possibly due to the differing amount of average meat consumption.
However, red meat intake does not impact most glycemic and insulinemic factors in type 2 diabetes (16, 17). This may be explained by other factors, such as lifestyle choices and body weight.
- Cancer: Carcinogenicity of the consumption of red meat and processed meat
- Red and processed meat consumption and mortality: dose–response meta-analysis of prospective cohort studies