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A Low Methionine Diet May Help Starve Cancer Cells

July 8, 2014 by Michael Greger M.D. in News with 12 Comments

A Low Methionine Diet May Help Starve Cancer Cells

When designing an antibiotic, we can’t create a drug that destroys DNA because that’s something that both humans and bacteria share in common. It would kill bacteria, but it might kill us, too. Instead, many antibiotics work by attacking bacterial cell walls, which is something bacteria have that we don’t.

Similarly, antifungals can attack the unique cell walls of fungus. Pesticides can work by attacking the special exoskeleton of insects. But fighting cancer is harder because cancer cells are our own cells. So fighting cancer comes down to trying to find and exploit differences between cancer cells and normal cells.

Forty years ago, a landmark paper was published showing for the first time that many human cancers have what’s called “absolute methionine dependency,” meaning that if we try to grow cells in a Petri dish without giving them the amino acid methionine, normal cells thrive, but without methionine, cancer cells die. Normal breast cells grow no matter what, with or without methionine, but cancer cells need that added methionine to grow.

What does cancer do with the methionine? Tumors use it to generate gaseous sulfur-containing compounds that, interestingly, can be detected by specially trained diagnostic dogs. There are mole-sniffing dogs that can pick out skin cancer. There are breath-sniffing dogs that can pick out people with lung cancer. Pee-sniffing dogs that can diagnose bladder cancer and–you guessed it–fart-sniffing dogs for colorectal cancer. Doctors can now bring their lab to the lab!

It gives a whole new meaning to the term “pet scan.” :)

Methionine dependency is not just present in cancer cell lines in a Petri dish. Fresh tumors taken from patients show that many cancers appear to have a biochemical defect that makes them dependent on methionine, including some tumors of the colon, breast, ovary, prostate, and skin. Pharmaceutical companies are fighting to be the first to come out with a drug that decreases methionine levels. But since methionine is sourced mainly from food, a better strategy may be to lower methionine levels by lowering methionine intake, eliminating high methionine foods to control cancer growth as well as improve our lifespan (see Methionine Restriction as a Life-Extension Strategy).

Here’s the thinking: smoking cessation, consumption of diets rich in plants, and other lifestyle measures can prevent the majority of cancers. Unfortunately, people don’t do them, and as a result hundreds of thousands of Americans develop metastatic cancer each year. Chemotherapy cures only a few types of metastatic cancer. Unfortunately, the vast majority of common metastatic cancers, such as breast, prostate, colon, and lung, are lethal. We therefore desperately need novel treatment strategies for metastatic cancer, and dietary methionine restriction may be one such strategy.

So, where is methionine found? In my video, Starving Cancer with Methionine Restriction, you can see a graph of foods with their respective methionine levels. Chicken and fish have the highest levels. Milk, red meat, and eggs have less, but if we really want to stick with lower methionine foods, fruits, nuts, veggies, grains, and beans are the best. In other words, “In humans, methionine restriction may be achieved using a predominately vegan diet.”

There are also compounds in animal products that may actually stimulate tumor growth. See, for example, How Tumors Use Meat to Grow: Xeno-Autoantibodies. Animal protein may also boost levels of the cancer-promoting hormone IGF-1 (The Answer to the Pritikin Puzzle). Combined, this could all help explain why plants and plant-based diets have been found effective in potentially reversing some cancer processes. See Cancer Reversal Through Diet?, Strawberries versus Esophageal Cancer, and Black Raspberries versus Oral Cancer.

So why isn’t every oncologist prescribing a low-methionine diet? One researcher notes that “Despite many promising preclinical and clinical studies in recent years, dietary methionine restriction and other dietary approaches to cancer treatment have not yet gained wide clinical application. Most clinicians and investigators are probably unfamiliar with nutritional approaches to cancer.” That’s an understatement! “Many others may consider amino acid restriction as an ‘old idea,’ since it has been examined for several decades. However, many good ideas remain latent for decades if not centuries before they prove valuable in the clinic….With the proper development, dietary methionine restriction, either alone or in combination with other treatments, may prove to have a major impact on patients with cancer.”

Why might the medical profession be so resistant to therapies proven to be effective? The Tomato Effect may be partially to blame.

In my video, Anti-Angiogenesis: Cutting Off Tumor Supply Lines, researchers come to the same plant-based conclusion from a different perspective, starving cancers of their blood supply.

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death and More Than an Apple a Day.

Image Credit: PNNL – Pacific Northwest National Laboratory / Flickr

How Animal Proteins May Trigger Autoimmune Disease

July 3, 2014 by Michael Greger M.D. in News with 15 Comments

Although slaughterhouse workers with the most poultry exposure appear to suffer the greatest excess mortality (see Poultry Exposure Tied to Liver and Pancreatic Cancer), increased risk of death from cancer is also found in other slaughterplant workers. This research goes back decades and shows higher cancer rates in butchers, slaughterhouse workers, meat cutters, and those working in meat processing plants.

The increased risk for meat industry workers in developing and dying from cancer “may be due to animal-to-human viruses or antigenic stimulation through chronic exposure to animal protein.” Cancer-causing virus exposure could also help explain why those who eat meat have higher cancer rates. There’s even a retrovirus associated with cancerous fish tumors, which has been speculated as the cause for increased cancer rates in American seafood workers.

Growing up on a livestock farm is associated with higher rates of blood-borne cancer, lymphomas and leukemia. Worst, though, is growing up on a poultry farm, which is consistent with chicken consumption being most closely tied to these cancers. Eating a quarter of a chicken breast daily is associated with a doubling or tripling of risk for these cancers (see EPIC Findings on Lymphoma). Growing up on a farm raising only plant crops, however, is not associated with blood-borne cancers.

What about growing up with dogs and cats? See Pets & Human Lymphoma and Are Cats or Dogs More Protective for Children’s Health? You still probably shouldn’t eat them, though (see Foodborne Rabies).

Researchers are finally able to start connecting the dots. High levels of antibodies to avian leucosis/sarcoma viruses and reticuloendotheliosis viruses in poultry workers provide evidence of infectious exposure to these cancer-causing poultry viruses. The highest levels were found not in the eviscerators, or gut-pullers, or those that hang the live birds, but among the line workers that just cut up the final product.

In an attempt to narrow down which diseases were associated with which meat, researchers tried separating out those in pig slaughtering and pork processing. “One of the primary sources of concern in using pig organs and tissues as transplants in humans is the fear of introducing zoonotic infections” from animals. We’re concerned about what’s called PERV transmission, the pig-to-human transmission of porcine endogenous retroviruses, raising theoretical concerns about cancer, immunological, and neurological disorders. However, we don’t need to get a pig transplant to be exposed. PERVs are also found in blood, so people exposed to pig blood may be exposed to the virus.

The main finding unique to the pork study (profiled in my video Eating Outside Our Kingdom), which was not found in beef and sheep processing, was the significant excess of deaths “from senile conditions such as Alzheimer’s disease.” It reminds me of all those poor pork brain extraction workers. You think your job is bad? How would you like to work at the “head-table”? Well, that doesn’t sound so bad until you learn it’s where, through the “unbridled use of compressed air in the pursuit of maximum yield of soft tissue,” they remove the brains of severed swine heads.

In one study, researchers noted that as the line speeds increased, “the workers reported being unable to place the skulls completely on the brain removal device before triggering the compressed air, causing greater splatter of brain material.” The aerosolized “mist of brain” is suspected to be the cause of dozens of cases of inflammatory neurological disease in workers who started with symptoms as mild as pain, tingling, and difficulty walking, and ended up so bad that doctors had to put them in a coma for six weeks because of unrelenting seizures.

At first researchers thought it was a brain parasite, but now it’s known to be an auto-immune attack triggered by the exposure to aerosolized brain. A similar mechanism has been blamed for meat proteins triggering inflammatory arthritis in people eating meat. By eating fellow animals, we are exposed not only to fellow animal diseases, but to animal tissues that our body may mistake as our own. This may be one advantage to eating a more plant-based diet. By eating outside of the animal kingdom—dipping into the plant or mushroom kingdoms for supper—not only do we not have to worry about getting something like Dutch elm disease, but we can be reassured by the fact that never has an “auto-immune polyradiculoneuropathy” been blamed on a head… of lettuce.

For more on foodborne illnesses one can contract from fellow animals, see, for example:

Probably the strangest example of this whole concept is the Neu5Gc story. A 7-part video series worth checking out:

  1. Cancer as an Autoimmune Disease
  2. Clonal Selection Theory of Immunity
  3. Clonal Deletion Theory of Immunity
  4. The Inflammatory Meat Molecule Neu5Gc
  5. How Tumors Use Meat to Grow: Xeno-Autoantibodies
  6. Nonhuman Molecules Lining Our Arteries
  7. Meat May Exceed Daily Allowance of Irony

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death and More Than an Apple a Day.

Image Credit: vgm8383 / Flickr

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