Plant-based diets may help rheumatoid arthritis by decreasing exposure to an inflammatory "Trojan horse" compound found in animal products called Neu5Gc. On Tuesday in my post How Tumors Use Meat to Grow I talked about the role Neu5Gc may play in stimulating breast cancer growth, but what about inflammation in our joints?
For those of you who have been following my work since the beginning, you'll remember back in 2003 I covered a landmark paper in the Proceedings of the National Academy of Sciences entitled "Human intake and incorporation of an immunogenic nonhuman dietary sialic acid." They took autopsy samples and discovered proof of Neu5Gc in human tumors. In my video The Inflammatory Meat Molecule Neu5Gc you can see it stained brown in human breast cancer, melanoma, brain tumors, and ovarian cancer.
The presence of Neu5Gc in human tumors mystified researchers, because human beings are genetically unable to produce this substance. But other animals can. Maybe, the researchers proposed, human beings absorbed it from eating these other animals? So they put it to the test.
Because Neu5Gc is found in animals and animal products, the researchers had to first eat vegan for a few days to clear their system (including no animal-derived ingredients in foods or drugs or shampoo), and then they basically drank a glass of diluted pig mucous. Within days this invading meat molecule could be found oozing from their bodies, in their saliva, urine--even their hair clippings. They concluded: "Because NeuGc-type compounds are not found in plants, and Neu5Gc is not synthesized by microbes, the dietary source of Neu5Gc must be foods of animal origin." They proposed that the metabolic incorporation of this molecular "Trojan horse" from animal products may be contributing to the higher rates of cancer and heart disease in those that eat meat and dairy.
Why heart disease too? If you check out my 3-min video Nonhuman Molecules Lining Our Arteries, you'll see that this foreign meat molecule tends to accumulate not only in the lining of hollow organs (where carcinomas like breast cancer develop inside your glands), but also in the lining of blood vessels. This may be contributing to the hardening of our arteries, the #1 killer of men and women in the United States.
Inflammation is one of the three steps en route to fatal heart disease. See Arterial Acne, Blocking the First Step of Heart Disease, and Making Our Arteries Less Sticky. Antioxidants found predominantly in plants may also decrease inflammation within the body. Nuts may be particularly useful in this regard.
The absorption of the inflammatory molecule Neu5Gc from animal foods may explain why vegetarian diets seem to improve rheumatoid arthritis. Maybe that's why rheumatoid arthritis is not present in most other great apes. Maybe the incorporation of this reactive alien molecule into inflamed tissue such as arthritic joints could be aggravating arthritis. What we do know is that if you take animal products away, rheumatoid sufferers can feel better within weeks-see Diet & Rheumatoid Arthritis and Preventing Arthritis.
Bacterial endotoxins are another reason animal products may trigger an inflammatory immune reaction. See The Leaky Gut Theory of Why Animal Products Cause Inflammation, The Exogenous Endotoxin Theory, and Dead Meat Bacteria Endotoxemia.
Beyond the putative role of nonhuman Neu5GC as a potential molecular link between diet, autoreactive antibodies, and the progression of human cancer and heart disease, I close out the Neu5Gc story with a 3-min. video entitled Meat May Exceed Daily Allowance of Irony. It turns out that consuming Neu5GC may set children up for life-threatening reactions to E. coli toxins originating in the same animal products. The researchers ask if this is "poetic justice" for meat eaters. Not when it's a major cause of acute life-threatening kidney failure in children. For more on E. coli, see Fecal Bacteria Survey and Chicken Out of UTIs.
My exploration into Neu5GC spanned a seven video series (starting with Cancer as an Autoimmune Disease). If you'd rather these more extensive probes than my one-off videos, I've done similar in-depth series on reversing cancer cell growth, why animal products cause inflammation, changing vitamin D recommendations, arugula athleticism, why nuts don't appear to cause expected weight gain, as well as the latest dietary guidelines.
-Michael Greger, M.D.