Those who consume large amounts of red and processed meats are at greater risk of developing cardiovascular disease and cancer according to the results of a new study, published in the Archives of Internal Medicine earlier this month. The researchers calculated that almost 10% of total deaths could be prevented if individuals reduce their red meat consumption to less than half a serving, or 42 grams, a day.
The research, led by Dr An Pan of the Harvard School of Public Health, involved the analysis of two large prospective studies, the Health Professionals Follow-up Study, which involved 51,529 men aged 40-75 years, and the Nurses’ Health Study, which involved 121,700 women.
The researchers found a strong association between red meat intake and all cause mortality. After adjustment for a number of potential confounders, those in the highest quintile for red meat consumption had 30% higher all cause mortality than those in the lowest quartile of red meat intake. The top quintile of red meat eaters averaged 2.07 and 2.17 servings for men and women respectively while those in the bottom quintile averaged just 0.25 and 0.51 servings for men and women.
The researchers also looked at the risk of cardiovascular death and cancer death across different levels of red meat consumption. Cardiovascular disease was more stongly related to red meat consumption than cancer. Those in the top quintile for red meat consumption had 40% higher risk of dying from cardiovascular disease and 19% increased cancer mortality than those in the bottom quintile.
The health risks appeared to be slightly stronger for processed red meat compared to unprocessed red meat. Each additional serving of processed red meat increased the risk of all-cause death by 20% compared to 13% for each additional serving of un-processed meat.
The graph below shows the risk of cardiovascular disease and cancer across the 5 quintiles of red meat intake.
The researchers also looked at the effects of substituting a serving of red meat for another food group. Substituting a daily serving of red meat for a serving of nuts reduced all cause mortality by 19%. Substituting for a serving of whole grains or poultry reduced all cause mortality by 14%, legumes and low fat dairy products cut mortality by 10%, while fish reduced risk by 7%.
The authors calculated that as many as 9.3% of deaths in men and 7.6% in women could be prevented if all individuals in the study had consumed less than 0.5 servings (42g) of red meat a day however just 22.8% of men and 9.6% of women in the study consumed less than this.
The current per capita intake of red meat in the USA is around 75g per day. The intake of red meat rose dramatically during the early and middle part of the 20th century, a time when rates of heart disease and cancer were also increasing. While consumption of red meat has levelling off somewhat, it still makes up more than half of all meat products consumed.
One possible explanation for the health risks associated with red meat could be the large amounts of heme iron found in red meat. Although iron plays important roles in several body functions, excessive iron intake, particularly of heme iron, the form found in animal products, has been linked to several chronic diseases including diabetes, heart disease, and various cancers.
Meat, cooked at high temperatures, produces large amounts of Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs), which have been shown to be carcinogenic in various laboratory studies. Several studies have linked consumption of barbecued and pan fried red meat with several forms of cancer, particularly pancreatic and colorectal cancers.
In addition to this, fatty cuts of red meat are a significant source of saturated fat which increases LDL cholesterol levels and subsequently the risk of heart disease.
Finally, processed meats often contain high amounts of N-nitroso compounds. Although a firm link has not been established, there is some suggestion that N-nitroso compounds play a role in the development of cancer. Research published last year, using data from the European Prospective Investigation into Cancer and Nutrition (EPIC) study, found that high intake of N-nitrosodimethylamine (NDMA), which is a N-nitroso compound, substantially increased the risk of gastrointestinal cancers, and in particular, rectal cancers.
It is important to note that the excess risks of cancer and cardiovascular disease associated with red meat consumption are still relatively low compared to other risk factors for chronic disease such as obesity, a sedentary lifestyle, and tobacco smoking, however those who consume large amounts of red meat, in excess of two servings or 160g per day, should look to reduce their consumption. When possible, choose low fat cuts of red meat and use slow cooking methods rather than pan-frying or barbecuing the meat.
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