Red meat

In gastronomy, red meat is commonly red when raw and a dark color after it is cooked, in contrast to white meat, which is pale in color before and after cooking. In culinary terms, only flesh from mammals or fowl (not fish) is classified as red or white. In nutritional science, "red meat" is defined as any meat that has more of the protein myoglobin than white meat. White meat is defined as non-dark meat from fish or chicken (excluding the leg or thigh). Some meat, such as pork, is classified as "white meat" under the common or culinary definition, but as "red meat" under the nutritional definition.
Definition.
Under the culinary definition, the meat from adult or "gamey" mammals (for example, beef, horse meat, mutton, venison, boar, hare) is red meat, while that from young mammals (rabbit, veal, lamb) is white. Poultry is white, as well as duck and goose. Most cuts of pork are red, others are white. Game is sometimes put in a separate category altogether. (French: "viandes noires" — "dark meats".) Some meats (lamb, pork) are classified differently by different writers.
According to the United States Department of Agriculture (USDA), all meats obtained from mammals (regardless of cut or age) are red meats because they contain more myoglobin than fish or white meat (but not necessarily dark meat) from chicken. Some cuts of pork are considered white under the culinary definition, but all pork is considered red meat in nutritional studies. The National Pork Board has positioned it as "the other white meat", profiting from the ambiguity to suggest that pork has the nutritional properties of white meat, which is considered more healthful.
Cultural and social aspects.
Across many cultures, it is traditional to eat meat at gatherings or celebrations. Consumption in the United States increased in 2018.
Nutrition.
Red meat contains large amounts of iron, creatine, minerals such as zinc and phosphorus, and B-vitamins: (niacin, vitamin B12, thiamin and riboflavin). Red meat is a source of lipoic acid.
Red meat contains small amounts of vitamin D. Offal such as liver contains much higher quantities than other parts of the animal.
In 2011, the USDA launched MyPlate, which did not distinguish between kinds of meat, but did recommend eating at least 8 oz (227 grams) of fish each week. In 2011, the Harvard School of Public Health launched the Healthy Eating Plate in part because of the perceived inadequacies of the USDA's recommendations. The Healthy Eating Plate encourages consumers to avoid processed meat and limit red meat consumption to twice a week because of links to heart disease, diabetes, and colon cancer. To replace these meats it recommends consuming fish, poultry, beans or nuts.
Health effects.
Understanding the health impact of red meat is difficult because it is not a uniform product, with effects varying based on fat content, processing and preparation. One analysis showed that processed red meat is linked to slightly higher mortality, mainly due to cardiovascular diseases and cancer.
Processed meat.
In 2015, the International Agency for Research on Cancer of the World Health Organization (WHO) classified processed meat as carcinogenic to humans (Group 1), based on "sufficient evidence in humans that the consumption of processed meat causes colorectal cancer." 
Processed meat is that which has undergone salting, curing, fermentation, smoking, or other processes to enhance flavor or improve preservation. It includes bacon, ham, salami, pepperoni, hot dogs, and some sausages. Most processed meat contains at least some red meat. Nitrates and nitrites found in processed meat can be converted by the human body into nitrosamines that can be carcinogenic, causing mutation in the colorectal cell line, thereby causing tumorigenesis and eventually leading to cancer. In its Press Release 240 (16 Oct. 2015) the International Agency for Research on Cancer, based on a review of 800 studies over 20 years, concluded that processed meat is definitely carcinogenic (Group 1) and found that for each additional 50g of processed meat consumed per day, the risk of colorectal cancer increased by 18% (up to a maximum of approximately 140g); it also found that there appeared to be an increase in gastric cancer but this was not as clear.
A 2016 literature review found that for the each additional 50g per day of processed meat consumed, the risk increased 4% for total prostate cancer, 8% for cancer mortality, 9% for breast cancer, 18% for colorectal cancer, 19% for pancreatic cancer, 13% for stroke, 24% for cardiovascular mortality and 32% for diabetes.
Red meat.
In 2015, the International Agency for Research on Cancer concluded that red meat is probably (Group 2A) carcinogenic to humans.
Studies that differentiate between processed and fresh red meat have failed to find a link between unprocessed red meat consumption and heart disease. A meta-analysis published in 2010 involving around one million people who ate meat found that only processed meat had an adverse risk in relation to coronary heart disease (CHD). The review suggested that the "differences in salt and preservatives, rather than fats, might explain the higher risk of heart disease and diabetes seen with processed meats, but not with unprocessed red meats."
Several studies have found a correlation between unprocessed red meat and the occurrence of CHD and certain types of stroke and have controlled for various confounding risk factors. A study of 84,000 women, over a period of 26 years, finds that those with the highest intake of unprocessed red meat have a 13% increased risk of CHD.
Unprocessed red meat intake is tentatively associated with an increased risk of type 2 diabetes, but the link is weaker and less certain than the link between processed red meat and diabetes. Other findings have suggested that the association may be due to saturated fat, trans fat and dietary cholesterol, rather than red meat per se. 
Cancer.
In 2015, the International Agency for Research on Cancer classified red meat as "probably carcinogenic to humans (Group 2A), based on limited evidence that the consumption of red meat causes cancer in humans and strong mechanistic evidence supporting a carcinogenic effect."
Another study in 2011 reported that for each additional 100g (up to a maximum of approximately 140g) of red meat consumed per day, the risk of colorectal cancer increased by 17%; there also appeared to be increased risk of pancreatic cancer and prostate cancer but the association was not as clear. Put in perspective, in the UK, 56 out of 1000 people who eat the lowest amount of red meat will develop colorectal cancer (5.6%) while 66 out of 1000 high-red meat eaters will develop colorectal cancer (6.6%) (1.17 x 5.6 = 6.6).
A meta-analysis in 2012 found an increased risk of gastric cancer with higher consumption of red or processed meat. Red meat itself contains certain factors that, under certain conditions, produce carcinogens like N-nitroso compounds (NOCs).
A 2016 literature review in "Journal of Internal Medicine" reported that for 100g or more per day of red meat consumed, the risk increased 11% for each of stroke and for breast cancer, 15% for cardiovascular mortality, 17% for colorectal cancer, and 19% for advanced prostate cancer. Another 2017 literature review indicated there are numerous potential carcinogens of colorectal tissue in red meat, particularly those in processed red meat products, such as N-nitroso compounds, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic amines (HCAs). Processed meat is more carcinogenic compared to red meat because of the abundance of potent nitrosyl-heme molecules that form "N"-nitroso compounds.
A 2019 meta-analysis concluded that the absolute effects of red meat on cancer and all cause mortality were very small and that the certainty of evidence was low. However, a commentary on the review argued that the certainty of evidence was instead of moderate to high quality.
Cardiovascular disease and diabetes.
A 2017 systematic review and meta-analysis of clinical research on stroke outcomes associated with meat consumption showed that total meat consumption, red meat consumption, and processed red meat consumption increased the risk of stroke by 18%, 11%, and 17%, respectively, while consuming white meat (chicken) reduced the risk of stroke by 13%. Factors associated with increased stroke risk from consuming red meat include saturated fats that increase levels of blood cholesterol, LDL cholesterol, triglycerides, and heme iron, which may precipitate atherogenesis in cerebral arteries, leading to stroke.
A 2017 review found that consuming a one-half serving of red meat daily was not associated with cardiovascular disease risk factors, such as total cholesterol, LDL, and hypertension. One study estimated that “substitutions of one serving of nuts, low-fat dairy, and whole grains per day for one serving of red meat per day were associated with a 16–35% lower risk of type 2 diabetes”.
Red meat consumption has been associated with higher fasting glucose and insulin concentrations, which are risk factors for type 2 diabetes. Daily consumption of 85 grams of red meat and 35 grams of processed red meat products by European and American consumers increased their risk of type 2 diabetes by 18-36%, while a diet of abstinence of red meat consuming whole grains, vegetables, fruits, and dairy was associated with an 81% reduced risk of diabetes.
Cooking.
Cooking any meat at a high temperature or smoking meat produces carcinogenic polycyclic aromatic hydrocarbon compounds and heterocyclic amines. The subgroups of heterocyclic amines compounds are amino-dimethylimidazo-quinoxaline (MelQx), amino-dimethylimidazo-quinoxaline (DiMelQx), and amino-methyl-phenylimidazo-pyridine (PhIP), which are mostly formed when meat is cooked at high temperatures. Benzo[a]pyrene (B[a]P) is another compound found in meat cooked at extremely high temperatures. Likely because of these factors, marinating fresh lean red meat and thoroughly cooking it at a low temperature will reduce the production of carcinogenic compounds and thereby lower the risk of colorectal cancer.