"The American Cancer Society, for example, notes that many studies have found “a link” between eating red meat and heightened risks of colorectal cancer. But it stops short of telling people that the meats cause cancer. Some diets that have lots of vegetables and fruits and lesser amounts of red and processed meats have been associated with a lower risk of colorectal cancer, the American Cancer Society says, but “it’s not exactly clear” which factors of that diet are important."
An estimate from the Global Burden of Disease Project - an international consortium of more than 1,000 researchers - claims that 34,000 cancer deaths per year worldwide are attributable to diets high in processed meat. This compares with about 1 million cancer deaths per year globally due to tobacco smoking and 600,000 a year due to alcohol consumption, it said.
Processed meats are those preserved by smoking, curing, or salting, or the addition of chemical preservatives. This includes bacon, ham, pastrami, salami, pepperoni, hot dogs, some sausages, and hamburgers (if they have been preserved with salt or chemical additives) and more. Particularly problematic are the nitrates that are added to these meats as a preservative, coloring, and flavoring. The nitrates found in processed meats are frequently converted into nitrosamines, which are clearly associated with an increased risk of certain cancers.
THE EVIDENCEHuffington Post:
A 2013 observational study is teasing out processed meat's effect in particular on health, and shows that not only is it the sort of person who eats a lot of processed meat that has the negative health risks, but the processed meat itself.
The study, published in the journal BMC Medicine and conducted by researchers from the University of Zurich, shows an association between processed meat and higher risks of dying from heart disease and cancer.
The results are based on an analysis of 448,568 men and women between ages 35 and 69, who did not have cancer and who had not suffered a stroke or heart attack when they entered the study. Researchers gathered information on their diets, exercise, body mass index and smoking status. The participants came from 10 countries.
Researchers found strong associations between unhealthy lifestyle choices and high consumption of processed meat; such lifestyle choices including eating little produce and being more likely to smoke (among men and women), and drinking higher amounts of alcohol (among men).
However, researchers were able to tease out processed meat consumption specifically to see how that affected risk of premature death. Even after taking into account other factors, processed meat consumption was still shown to raise risk of dying from heart disease and cancer.
"We estimated that 3.3 [percent] of deaths could be prevented if all participants had a processed meat consumption of less than 20 [grams] per day," the researchers wrote in the study. The Atlantic pointed out that 20 grams of processed meat is the equivalent of a "matchbook-sized portion" of sausage.
Meanwhile, researchers did not find an association between poultry consumption and increased risk of premature death. But take heart, meat lovers, the study was not all bad news -- researchers also found a small benefit from still including a bit of red meat in the diet. The Atlantic explains:
Eating little or no red meat, like beef and pork, was actually associated with higher all-cause mortality than very moderate consumption, presumably because red meat does contain important vitamins and nutrients (protein, iron, zinc, vitamins A and B, essential fatty acids). This range, the authors also believe, most accurately reflects people who attempt to optimize their diet, whereas vegetarian diets may be poorly balanced.
"If you eat lots of processed meat, try to vary your diet with other protein choices such as chicken, fish, beans or lentils," heart health dietitian Tracy Parker, of the British Heart Foundation, told BBC News.
Previously, processed meat has been linked with an increased risk of pancreatic cancer. A British Journal of Cancer study showed that people who eat an extra 50 grams of processed meat (the equivalent of a sausage) a day can raise the risk of the condition by 19 percent, and people who ate an extra 100 grams of processed meat a day can raise their risk by 38 percent. A 2007 analysis by the World Cancer Research Fund (WCRF) found that eating just one sausage a day can significantly raise your risk of bowel cancer. Specifically, 1.8 ounces of processed meat daily – about one sausage or three pieces of bacon – raises the likelihood of the cancer by 20 percent.
The risk continues to rise as processed meat consumption increases. Studies show that compared to eating no processed meat, eating 3.5 ounces every day – a large hot dog – increases colorectal cancer risk by 36%.
Another study from Harvard researchers showed that regularly eating processed meat could actually affect your body's ability to use and produce insulin -- thereby raising risk of Type 2 diabetes by 19% and increasing the risk of heart disease by 42%.
And in a study of 141 men undergoing in vitro fertilization (IVF) with their partners, no association was found between total meat consumption and successful fertilization through IVF. However, men who ate the least amount of processed meat (including sausage, bacon, and canned meat products) had a 28 percent higher rate of fertilization during IVF compared to those who ate the most. Those who ate the most poultry (and presumably less processed meats and possibly overall healthier diet) also had a13 percent higher fertilization rate than men who ate the least.
THE VERDICTNatural or organic hot dogs advertised as nitrate-free may not be much lower in nitrite — and some may even be higher than conventional hot dogs. Companies that label their products natural or organic must use natural sources of the preservatives, which usually come in the form of celery powder, celery salt, or celery juice, as celery is naturally high in nitrate, plus a starter culture of bacteria. This transforms the nitrate found naturally in the celery salt into nitrite, which cures the meat.
A 2011 study published in The Journal of Food Protection found that natural hot dogs had anywhere from one-half to 10 times the amount of nitrite of conventional hot dogs. A similar scenario exists for bacon. So, buying organic nitrate-free hot dogs is not necessarily going to reduce your nitrate exposure — although it will likely result in a higher quality food product in many other respects.
While processed meats are better off avoided, organic, pastured meats can be a healthy part of your diet. Some of the benefits of grass-fed and grass-finished beef, for instance, include higher levels of conjugated linoleic acid (CLA) and other healthy fats. It also has a more balanced ratio of omega-3 to omega-6. Unless labeled as 100% grass-fed, virtually all the meat you buy in the grocery store is CAFO beef, and tests have revealed that nearly half of the meat sold in US stores is contaminated with pathogenic bacteria — including antibiotic-resistant strains.
» PETA: "Meat! Now, with added gross things!" (Infographic)
» Mercola: Conventional Ground Beef is 3x More Likely to Contain Antibiotic-Resistant Bacteria
» Duckett et al., 2009: "Effects of winter stocker growth rate and finishing system"
» Wikipedia: Ractopamine