jueves, 21 de noviembre de 2019

Does Red Meat Shorten Lifespan?

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By Sara Ryding, B.Sc.Reviewed by Dr. Jennifer Logan, MD, MPH

Red meat can be an important source of protein, calories, and B vitamins. However, research suggests that red meat consumption is also associated with health risks. Detrimental effects include the development of cardiovascular disease and cancer, which leads to a shortened lifespan among those consuming more red meat.

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Diets and nutrition

The relationship between red meat, or meat in general, and health disorders has been debated during the 21st century. During a similar timeframe, red meat consumption has increased globally. In the United States, red meat is the most common type of meat consumed by the population.

Many studies have found deleterious effects of red meat consumption on cardiovascular health, diabetes, and cancer.

Red meat and health

Nutritional studies increasingly distinguish between unprocessed red meats (beef, pork, and lamb) and processed red meats (bacon, hot dogs, sausage, salami, bologna) to better clarify the possible deleterious effects of consuming these foods.

Red meat contains high levels of protein and fat, which has led some to hypothesize that saturated fat content and cholesterol may be contributing to the development of cardiovascular disorders, particularly when consumed in excess.

Another theory for why red meat has been associated with cardiovascular disorders is to do with its dietary iron content. Dietary iron and heme iron from red meat have been linked to higher rates of myocardial infarction and fatal heart disease. However, this has been disputed by other studies focusing on the saturation of iron-carrying cells, ferritins.

Colorectal cancer is the main form of cancer linked to red meat consumption, although several other types have also been linked. Irons have been linked to potential cancer risks, especially through heme iron and iron overload. These compounds promote the formation of N-nitroso compounds from nitrates, increasing colonic cytotoxicity, increased proliferation of colonic epithelial cells, and increased oxidative stress.

Cancer risks are also associated with other compounds in red meat. Carcinogenic compounds are present in red meat, and others are created during cooking at high temperatures. N-nitroso compounds, polycyclic aromatic hydrocarbons, and heterocyclic amines are all believed to be able to contribute to increased cancer risk.

Evaluating the evidence

Some studies showing correlations between red meat consumption and health disorders have been criticized for the study populations they chose because they had a high proportion of vegetarians in the study or because the researchers did not make a distinction between processed and unprocessed meat.

The importance of not differentiating between red meat and processed meat can depend on what is believed to cause the health disorders associated with eating meat. For example, saturated fats and heme iron have been identified as potential causation agents, but the levels of these are similar in both red meat and processed meats. Red and processed meats differ in sodium and nitrite levels, which are higher in processed meats.

Despite these criticisms, there is still ample evidence to suggest that red meat can increase the risk of cardiovascular disease, cancer, and overall mortality. In one long-term study (over the course of 28 years) that followed 121 000 participants, the researchers estimated that substituting one serving of other foods (fish, poultry, nuts, legumes, low-fat dairy, or whole grains), could decrease the risk of death by up to 19%.

One major variable that is often mentioned as a criticism of large-scale human studies is the choice of the population cohort. Many nutritional studies are conducted in the US, with a group comprised of mostly White participants.

These participants may have differential susceptibility to certain disorders or different lifestyles and dietary tendencies compared to other groups. Therefore, mortality estimates from red meat consumption could be either lower or higher in areas of the world or for non-White persons.

While some studies have received criticisms for focusing on communities with high vegetarianism, the criticism goes both ways. Many studies carried out on large cohort populations tend to have a bias towards moderate or high meat intake levels, thereby ignoring the possibility of lower risks with low or no meat consumption.

Recent studies have found that even low red meat intake is associated with an elevated risk of mortality and cardiovascular disease-related mortality compared to no red meat consumption.

Sources

Pan A. et al. (2012) Red meat consumption and mortality: results from two prospective cohort studies. Archives of Internal Medicine. https://doi.org/10.1001/archinternmed.2011.2287
Alshahrani S.M. et al. (2019). Red and processed meats and mortality in a low meat intake population. Nutrients. https://doi.org/10.3390/nu11030622