Does Eating Meat Cause Cancer?

If you’ve been here before, you know I eat a very plant-strong diet. I didn’t always, as I explained in my book, n of 1, a memoir of my cancer journey.

Prior to my diagnosis 30 years ago I was a hard-core carnivore, with no desire to change. I ate whatever and whenever I liked. And though I enjoyed broccoli with my steak, my go-to veggie staples were French fries and ketchup.

However, for the last three decades I’ve maintained the same approach to food, which closely resembles a Mediterranean diet: plant strong, a rainbow of colors—heavy on cruciferous, leafy greens, and root veggies—some whole grains, beans, nuts, seeds, legumes, lots of spices, herbs, and select cold water, cleanly sourced fish.

I’ve written about cancer and nutrition science and what I eat here.

In this article, I will explore what the current science says specifically about eating red meat and cancer risk. It will not include a deep dive on any connection between cancer and animal protein in general, such as poultry, fish, or dairy. (I plan to cover that in the near future.)

However, science is not a cut-and-dried process. Scientists often disagree, especially when it comes to diet.

Are Humans Natural Carnivores or Not?

Vegetarians and vegans argue that humans don’t have the physical characteristics of carnivorous animals (pointed teeth, claws, high levels of stomach acid, short digestive tracts, and so on). They assert that the science proves that vegetarians live longer.

A large Harvard Medical School study[1] seems to support that claim. Dietary habits were tracked for 120,000 Americans from the 1980s until 2012. Researchers concluded that eating red and processed meat was correlated to a higher all-cause mortality rate.

During the study period, 24,000 died, including 5,900 from cardiovascular disease and 9,500 from cancer. Those who ate the highest amounts of red and processed meats had the highest mortality rates (with men more adversely affected than women).

Although the Harvard researchers acknowledged that other factors could be involved, they recommended substituting, for one serving of red meat per day, other foods—like fish, poultry, nuts, legumes, low-fat dairy and whole grains. That alone, they calculated, could lower the risk of mortality by 7% to 19%. Further, they estimated that if the participants had all consumed less than half a serving per day (about 1.5 ounces) of red meat, 9.3% of the deaths in men and 7.6% of the deaths in women could have been prevented.

In addition, a large study on Seventh Day Adventists and all-cause mortality, suggested that vegetarians may have a longer lifespan than meat eaters,[2] noting that “results were more robust in males than females.” The hazard ratios (HR) revealed interesting results based on the various types of diets.

The best outcome (lowest HR) was for those who ate a pesco-vegetarian diet (pesco = fish). Also called “pescatarian,” this is the diet I follow, sans dairy. Second best was vegan, followed by vegetarian, ova-lacto-vegetarians, and semi-vegetarians coming in last. However, even semi-vegetarians lived longer than the meat eaters.

Many studies have specifically linked the consumption of red meat with certain types of cancer.[3], [4], [5]

As one example, a study of 172 nations correlated total meat intake, urbanization, and obesity with a huge upsurge in prostate cancer.[6]

Yet, other scientists disagree.

For example, colorectal cancer (CRC) is the second leading cancer diagnosis among women and third among men worldwide. United Kingdom Women’s Cohort Study published in 2018 (34,147 women, conducted over 17.2 years) concluded that there was no significant difference in CRC among those who ate red meat and those who didn’t.[7]

Enjoying this article? Subscribe so you don’t miss the next one. We’ll also send an excerpt from Glenn’s book, n of 1.

Another even larger UK study comparing vegetarians and meat eaters showed similar all-cause mortality rates between both groups.[8] In other words, no greater longevity for the vegetarians.

The large 2019 Netherlands Cohort Study found no association with (unprocessed) red meat consumption and higher all-cause mortality (although processed meat was correlated). Red meat was associated with cardiovascular disease and respiratory disease, but not cancer. Fish showed some association. But eating white meat and nuts were shown to have an inverse relationship (that is, not only “not harmful” but possibly beneficial) on cancer and all-cause mortality.[9]

However, multiple studies listed at progressreport.cancer.gov paint a different picture.[10] Red meat (beef, pork, and lamb) consumption is associated with increased cancers of the colon and rectum, and may also be linked to prostate and pancreatic cancer, as well as breast cancer.[11] Red meat consumption was also studied in Japan, with men more at risk of developing colorectal cancer than women.[12]

A 2019 meta-analysis concluded that eating white meat actually protected against gastric cancer, but concurred that red meat increased the risk.[13]

Dietary debates aside, I think we can all agree that, in general, most Americans (and many Europeans) eat far more meat than anyone metabolically needs.

Not all meat, however, is created equal.

Highly Processed = Highly Risky

For some time, researchers have warned that cancer risk increases dramatically when eating highly processed and charbroiled meats. Current research bears this out as well.[14], [15]

Highly spiced, salted, processed, and preserved meats such as sausages, hot dogs, bacon, and luncheon meats are associated with increased pancreas, colorectal,[16] lung,[25] and stomach cancer.[17] Other cancers linked to processed meats include cancers of the bladder[18] and head and neck.[19]

Processed meat manufacturers usually add nitrates and nitrites, which convert in the meat or in the body to cancer-causing N-nitroso compounds, or NOCs.

Ultimately, in 2018, the World Cancer Research Fund Network concluded that evidence was both strong and convincing that processed meat causes cancer (especially colorectal) and probable evidence that red meat does also.[20], [25]

Interestingly, animal studies revealed that adding a healthy fiber (inulin) and certain beneficial probiotics to the processed meats resulted in less cancer.[21]

Research also showed the healthy and protective benefits of eating more plants, even for those who ate red and processed meat. Those who (in addition to the processed meats) also ate more fruits, vegetables, whole grains, and fiber had a lower incidence of cancer and slower cancer development.[22]

A “hot-off-the-press” meta-analysis concurs. Just last month, the results of two major U.S. studies combined with 26 other cohort studies from around the world, concluded: Adults who eat five servings per day of fruits and vegetables live longer than those who only eat two.[23] The five servings were specified as two fruits (excluding juice) and three vegetables (excluding peas, corn, and potatoes). Regarding cancer, the risk was reduced by 10 percent.

How, you might wonder, can fruits and vegetables make such a difference?

The Importance of Terrain

We tend to think of land when we hear the word “terrain.” However, it means more than that. It can mean our internal micro-environment, and it reflects in our overall state of health.

For example, organic vegetables, which have the highest levels of nutrition,[24] are grown in soil that is rich in nutrients and biodiversity. It’s similar for our health.

The microbiome consists of a mind-boggling number of microorganisms that live in, on, and around us. That’s our “terrain,” and it has everything to do with our level of health and resistance to disease.

We’ve all heard of the healthy flora (probiotics) in the gut. We now know that most of our immune system resides in the gut. Scientists even called the gut the second brain, because it directly affects our mental and emotional state.

When this vast micro-community called our microbiome is in harmony, we experience health and a robust immune system. A healthy gut microbiome thrives on diversity[25]—which a variety of fruits and veggies can provide.

A healthy gut also needs non-soluble fiber (which is considered a prebiotic—providing the terrain probiotics needed to flourish). Sadly, the standard American diet (SAD) sorely lacks fiber. Meat has zero non-soluble fiber, which is why many heavy meat eaters are chronically constipated—never a good situation for health. Stagnation breeds unhealthy gut microbes, just as a swamp breeds mosquitoes.

As a cancer coach I consistently promote eating lots of varied colors of vegetables, including juiced (preferably organic or the Environmental Working Group’s “Clean 15”[26]). The vibrant colors and appealing fragrance of fruits and vegetables, at their peak, hint at the abundant nutrition within.

I often ask my clients if they know why veggies and fruits are different colors. I explain that the diverse phytonutrients or phytochemicals that provide this rainbow of color are what protect plants in their native habitat. These chemicals protect plants from drought, flood, and herbicides and pesticides. Many of these phytochemicals have also been shown to kill cancer cells in vitro—in test tubes and petri dishes.

Enjoying this article? Subscribe so you don’t miss the next one. We’ll also send an excerpt from Glenn’s book, n of 1.

Consuming clean, colorful plants protects against disease, including cancer. Their powerful phytonutrients and antioxidants offset toxic elements we take in, which damage the cells of our body.

What toxic elements, you ask? Charbroiled meats, for one…

Meat Cookery and Cancer

How meat is cooked makes a huge difference in how the body processes it.

Grilling or charbroiling meats creates heterocyclic amines (HCAs) and polycyclic amines (PCAs). These chemicals are associated with stomach cancer, as processed meats are linked to colorectal cancer.[27]

Benzo[a]pyrene, a polycyclic aromatic hydrocarbon (PAH), is a widespread environmental pollutant. We can’t avoid it completely, since we inhale it wherever combustible material is partially burned (fossil fuels, outdoor and indoor air, tobacco smoke, and more). But we can certainly avoid eating barbequed or charbroiled meat and fish, a dietary source of this cancer-causing toxin.[28], [29]

Yet, to my point above on the benefit of eating more fruits and vegetables, studies showed that chlorophyll, found in green vegetables, protects against cancer, even in the presence of PAHs.[30]

Another potentially toxic element in meat is inherent in its red color: heme iron (the source of the word hemoglobin). We need a certain amount of iron. But too much heme iron causes oxidation (a visual analogy would be like internal rust). Heme iron is also associated with colorectal cancer.[24]

Although heme iron is better absorbed than non-heme iron, if someone has an iron deficiency, plant source iron (non-heme) absorption is enhanced in the presence of Vitamin C, a potent antioxidant.[24] So, antioxidants not only counteract oxidative damage, they also enhance nutrient absorption.

As the public gradually became aware of the health risks of eating red and processed meat, demand for a meat-like alternative spawned a whole new industry.

The Evolution of “Fake” Meat

In the early history of imitation meat production, Asian cooks learned long ago to soak wheat flour to separate out the gluten (protein portion), and knead the gluten into a chewy meat-like texture. In modern times, the product was called seitan (pronounced “say-tahn”) and was popularized by vegetarians like the Seventh Day Adventists and proponents of the macrobiotic diet.

Looking to fill the demand, modern food manufacturers learned to spin plant proteins into long strands, which they “knit” together to mimic meat fibers. We now see new iterations, such as a meat-like, plant-based product that impossibly “bleeds,” another that goes “beyond,” and coming soon: animal-cell, lab-grown, “cultured” (or in vitro) meat.[31]

In some of these iterations, GMO ingredients may be present.[32] If non-meat products contain non-organic beans or grains, they are likely contaminated with glyphosate, a widely used herbicide, and a known microbiome disruptor[33] and carcinogen. As far as the in vitro “meat,” who knows?

Perhaps we should remember an old TV commercial advertising an oil-based food product. The manufacturers proposed that their spread was better than butter. In the ad, after blind-test fooling Mother Nature, her memorable punch line, delivered in an ominous voice with a stormy bolt of lightning, was: “It’s not nice to fool Mother Nature.”

Are we really so psychologically addicted to meat that we are willing to put whatever chemical or lab-grown concoction into our mouths that will fulfill that need to imitate a greasy burger (that “bleeds”!)?

Keeping it Simple

Our lives are complex enough. We want simple answers. But cancer is a multi-factorial process. Many factors contribute. Some of those factors, we may not be able to change.

But diet is one fairly simple thing we can. That is, so long as we can fully embrace our new way of eating. Your food must be satiating, delicious, and not make you feel any level of deprivation. Otherwise, it will become just “a diet” and not hardwired into your lifelong lifestyle.

If your diet is mostly plants, you get an abundance of enzymes, protective chlorophyll, antioxidants, phytonutrients, polyphenols, and beneficial fiber. You feel fuller with fewer calories. Your cells and mitochondria (energy generators inside your cells) are nourished with the “cellular codes” that your body was designed to recognize: real food nutrition.

This is what I eat, which has worked well for me.

And I’ve counseled hundreds of others who want to eat as I do.

Bon appétit.

Photo credit: bigstockphoto.com/DmitrievMikhail

Join my private Facebook Group Anticancer Thrivers—a community forum for achieving your best life while living with cancer.

References

[1] https://www.nih.gov/news-events/nih-research-matters/risk-red-meat

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4191896/

[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5400064/

[4] https://pubmed.ncbi.nlm.nih.gov/27367552/

[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6558667/

[6] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6171413/

[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6055763/

[8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4691673/

[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6451725/

[10] https://progressreport.cancer.gov/prevention/red_meat

[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5400064/

[12] https://pubmed.ncbi.nlm.nih.gov/28256076/

[13] https://pubmed.ncbi.nlm.nih.gov/30979076/

[14] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5400064/

[15] https://pubmed.ncbi.nlm.nih.gov/27869663/

[16] https://pubmed.ncbi.nlm.nih.gov/28646407/

[17] https://progressreport.cancer.gov/prevention/red_meat

[18] https://pubmed.ncbi.nlm.nih.gov/28070638/

[19] https://pubmed.ncbi.nlm.nih.gov/28382514/

[20] https://www.bmj.com/content/368/bmj.m511

[21] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6794276/

[22] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7468967/

[23] https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.120.048996

[24] https://pubmed.ncbi.nlm.nih.gov/20359265/

[25] https://pubmed.ncbi.nlm.nih.gov/32932258/

[26] https://www.ewg.org/foodnews/clean-fifteen.php

[27] https://www.wcrf.org/sites/default/files/Meat-Fish-and-Dairy-products.pdf

[28] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3475201/

[29] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3155323/

[30] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3475201/

[31] https://pubmed.ncbi.nlm.nih.gov/33758465/

[32] https://www.momsacrossamerica.com/gmo_impossible_burger_positive_for_carcinogenic_glyphosate

[33] https://www.theguardian.com/environment/2018/may/16/glyphosate-shown-to-disrupt-microbiome-at-safe-levels-study-claims