Why might someone choose not to eat meat?
From ethical contentions about factory farming to concerns over environmental and personal health, the personal reasons to reduce or abstain from meat consumption has inspired at least 7.8 million Americans to adopt a vegetarian diet and lifestyle.
Personal health tops the list for many vegans and vegetarians alike, as well as some of the 22.8 million health-conscious consumers who endorse a "vegetarian-inclined" diet. And as plant-based diets grow in popularity, there's no question we'll continue to see reams of research backing them up.
Heart disease, stroke, acne—these are just some of the health concerns linked with meat consumption, according to hundreds of studies spanning decades. Even one of the most pressing chronic health conditions of our time—cancer—shares a troubling correlation to meat-eating. And lest we forget: according to the World Health Organization, cancer is the second leading cause of global deaths. In 2018, the disease claimed the lives of more than 9.6 million people.
Could cutting back on meat consumption—if not eliminating it altogether—save many of these lives? Let's see what the evidence has to say.
The Research-Backed Association Between Meat Consumption and Certain Types of Cancer
1. Breast Cancer
In 2014, Harvard School of Public Health released the results of a prospective cohort study involving over 88,000 women. Compared to women who ate just one serving of red meat per week (including beef, pork, and lamb), women who ate 1.5 servings of red meat per day were 22% more likely to be diagnosed with breast cancer. If this correlation isn't shocking enough, the researchers also found that for every additional serving of daily red meat, a woman's breast cancer risk increased by another 13%.
A more recent study from the International Journal of Cancer involving over 42,000 women produced similar results. In this study, women who ate the most amount of red meat were about 23% more likely to be diagnosed with breast cancer compared to women who ate the least amount.
This study also contained evidence to suggest that replacing red meat with poultry may be cancer-protective—although keeping animal products in the diet may not be necessary or even optimal, anyway. We see this in a 2011 review published in Cancer Management and Research, which found that vegetarian and plant-based diets appear effective at reducing cancer-risk by a minimum of at least 10-12%.
2. Colorectal Cancer
Also known as bowel cancer or colon cancer, colorectal cancer ranks third as leading types of cancer worldwide. Strong evidence links both red meat consumption and processed meat consumption (including bacon, pepperoni, ham, and sausage) to an increased risk of colon cancer. This includes a 2015 systematic review of 10 meta-analyses published in Oncology Reviews, which found that people who eat meat may be up to 20 to 30% more at risk for colon cancer.
Additional research commissioned by Australia's Cancer Council estimated that in 2010, 1 in 6 new bowel cancer cases were directly associated with excessive consumption of red and processed meats.
3. Other Types of Cancer (Liver, Lung, and Esophageal)
A large prospective cohort study published in a 2007 volume of PLoS Medicine determined that meat consumption increased the risk of a wide range of cancers, including liver, esophageal, and lung—in some cases by as much as 60%. The paper also cites other data connecting meat to many other types of cancer, including:
- Pancreatic: the British Journal of Cancer published a 2012 meta-analysis of 11 prospective studies featuring a total of 6,643 participants and found that eating about 50 grams of processed meat per day (one serving) was associated with a 19% increased risk of pancreatic cancer.
- Cervical: a 2018 paper published in Nutrients found that women who ate a typical "Western" diet—classically high in red and processed meats, among other foods—were more likely to become infected by high-risk human papillomavirus (HPV), which is linked with an increased risk for cervical cancer. Meanwhile, women who followed a Mediterranean diet (largely plant-based and high in whole grains, vegetables, and fruits) seemed less likely to acquire the infection.
- Prostate: healthy men who eat red meat, poultry, and especially eggs may significantly increase their risk of lethal prostate cancer, confirmed a 2011 prospective study from Cancer Prevention Research; the study followed over 27,600 men for 14 years and found that eating at least 2.5 eggs per week increased a man's risk of developing deadly prostate cancer by more than 80% compared to men who ate less than 0.5 eggs per week!
- Kidney: eating around 4.5 ounces of red meat per day (roughly equivalent to one hamburger) increased the risk of renal cell carcinoma, found a 2012 prospective study published in the American Journal of Clinical Nutrition.
- Stomach/gastric cancer: a 2013 meta-analysis from PLoS One determined that processed and red meat intake significantly increased the risk of stomach cancer.
- Oral cancer: PLoS One published a meta-analysis in 2014 involving 12 studies and over 500,000 subjects saw that high consumption of processed meat was correlated with a 91% increased risk of oral cavity and oropharyngeal cancer.
Quite the sobering ream of research, isn't it?
Importantly, many major organizations are taking note. For instance, the World Health Organization classifies red meat as "probably carcinogenic" (Group 2A). Meanwhile, processed meat is considered carcinogenic (Group 1), given the strong evidence to support the claim (other things that fall into Group 1 category include asbestos and tobacco).
In other words: both red meat and processed meat may increase the risk of cancer in humans. Possible explanations include exposure to hormones, increased saturated fat consumption, and unhealthy cooking methods (e.g., grilling and frying, which pose additional health risks), but further research is on-going.
No matter what's motivating you to cut back on or eliminate meat in your diet, the good news is that it's still easy and affordable to make delicious and nutrient-rich vegan and vegetarian meals. Need some inspiration? Try out our vegan cookbook and check back on our website regularly for new recipes!