How Tumors Use Meat to Grow

Certain cancers—like breast cancer—can be thought of in part as an autoimmune disease. When people get heart or kidney transplants, they must be given immunosuppressive drugs to prevent rejection of the new organ. What do you suppose happens to cancer rates in those individuals who have their immune systems suppressed? Well, for some types of cancer, like skin cancer, the risk goes up. This supports the so-called immune surveillance theory—the idea that our immune system acts as a natural defense system for keeping cancer under control (see a cool video of immune cells taking on a cancer cell here). This could explain why, as we age and our immune function declines, our risk of cancer goes up.

The problem with the immune surveillance concept is that for some cancers, suppressing immune function decreases risk. After a kidney transplant, though your skin cancer risk may go up, your breast cancer and rectal cancer risk goes down. Why would people with depressed immune systems have less cancer? This led to a new theory of cancer I explore in my 4-min. video Cancer as an Autoimmune Disease.

The only reason the immune system is even able to pick out cancerous cells from noncancerous cells is because tumors express foreign looking molecules that stimulate our immune system. Why would tumors do that? Why would cancer cells go out of their way to wave a red flag around saying, “Hey, come get me!”? We think it’s because cancer tends to thrive in a setting of low level inflammation. In the video I show a number of examples of chronic inflammation leading to cancer–ulcerative colitis to colon cancer, chronic pancreatitis to pancreatic cancer, chronic hepatitis to liver cancer, and stomach inflammation to stomach cancer. Oftentimes the body’s inflammatory immune response can further cancer’s agenda.

By inciting an immune response, cancer creates its own inflammation, which may stimulate angiogenesis, the formation of new blood vessels to bring blood to the tumor and help it grow. This may explain the mystery surrounding Kaposi’s sarcoma, a cancer affecting those with AIDS. When you start treating AIDS and the immune system starts to recover you can actually see a flare in the cancer.

So what are the dietary implications of this new autoimmune theory of cancer? See my video pick above. In short, there’s a molecule called Neu5Gc found in nonhuman animals but not made by the human species. Cancerous breast tumors appear to incorporate this molecule that women consume in meat and dairy to trick their immune systems into creating the environment of low-grade inflammation that breast cancer thrives in. Our own cancer may use what we feed on to get what it feeds on.

For more on Neu5Gc, one of the most fascinating topics of modern day nutrition, see my 4-min. video The Inflammatory Meat Molecule Neu5Gc.

Why else might those eating plant-based diets have lower risk of all cancers combined? Kathy Freston wrote a good summary. It could be due to diminished exposure to IGF-1, heme iron, inflammation, virusesantibioticssaturated fat, nitrosamines, and arachidonic acid associated with animal product consumption. Or it could be the DNA repair, cellular stress defenses, anti-inflammatory properties, soylignansphytonutrients, and fiber associated with healthy plant food consumption. It’s probably both, so it’s not enough to just eat vegan—we need to eat our veggies too.

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 presentation Uprooting the Leading Causes of Death.

Image credit: Pulmonary Pathology via Flickr

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How Do Plant-Based Diets Fight Cancer?


John W
John W9 months ago

Thanks, definitely cutting out meat and animal products. Also going to eat more turmeric

W. C
W. C10 months ago

Thank you.

William C
William C10 months ago


Jeanne Rogers
Jeanne Rabout a year ago

Thank you for sharing.

Mary T.
Mary T4 years ago

thanks for the information

Marsha F.
Marsha F4 years ago

Thank you. I'm glad someone is finally saying this. Based on my own experience, I've been convinced for a long time that there was an autoimmune/inflammatory connection to breast cancer. I have sarcoidosis, which is an autoimmune illness that causes severe inflammation and an overactive immune response. I also have/have had breast cancer, and when I have sarcoidosis flare ups, the breast cancer gets worse.

John B.
John B4 years ago

Thanks Dr. Greger for sharing this very interesting info.

Sue H.
sue H4 years ago

Some good information and food for thought... lots to learn on this subject. Eating as "clean" and organic as possible is the best we can do for ourselves and the planet.

Erica B.
Erica B4 years ago

I should add to my last comment this...that not only factory farmed meats (which are tainted with pesticides, antibiotics, and sometimes hormones) can cause increased cancer rates...any produce that isn't organic is risking your health, too. Processed foods also risk an increase in your chances of developing cancer. I would venture to say that the majority of vegans are careful about their food choices, so as well as not eating factory farmed meats, they are also avoiding processed foods and non-organic produce, which all contribute to cancer development.

Anyway, it isn't the TYPE of food being eaten that increases cancer is how that food is TREATED. If people ate humane, organically raised animal products, organic produce, and avoided processed foods, we could put the kibosh on the disastrous increase in cancer rates. To go even further, if we could eliminate many of the industrial toxins we come in contact with daily, such as what you find in synthetic materials (clothing, carpeting, wallpapers and paints, cleaning products, etc.), we could realistically see the complete demise of some forms of cancer. Most don't want to live in a mud hut with a grass roof, but we CAN use all-natural cleaning products, naturally dyed organic cotton and wool clothing, carpeting, bedding, and furniture coverings, and a bajillion other products available to us...if we just LOOK!

Erica B.
Erica B4 years ago

I would bet my last dollar that the so-called scientific theories of "doctor" Greger don't take into account that food animals treated with hormones, as well as the overuse of antibiotics and pesticides in those animals, is the REAL culprit in the rate of cancer among meat-eaters. It isn't convenient for proponents of veganism to admit that organically raised food animals are no more likely to increase cancer rates than a head of broccoli. I am a vegetarian, and if I can see the lies in this article, I would think the majority of the thinking population would too.