The cause of rheumatoid arthritis has baffled researchers for decades. The immune system is involved, of course, but what triggers the immune system in the first place? Researchers are starting to find answers in an unlikely place: the human gut. Mounting evidence suggests the bacteria that live in the human gut may be the trigger of rheumatoid arthritis. Do gut bacteria also hold a cure?
What Is Rheumatoid Arthritis?
Rheumatoid arthritis is a chronic disease that causes painful swelling in the joints. The disease usually starts in the hands and feet and works its way toward central joints over time. Without effective treatment, rheumatoid arthritis can cause severe deformity and disability. Currently, the most effective treatments for rheumatoid arthritis are drugs that suppress the immune system.
What Causes Rheumatoid Arthritis?
No one knows for sure what causes rheumatoid arthritis. Rheumatoid arthritis starts in people with the right (or wrong) combination of genetic factors and environmental exposures.1 In other words, people who are genetically predisposed to developing the disease, who then have experienced “insults,” will develop rheumatoid arthritis. Once the disease starts, however, it is self-perpetuating, which means it will keep getting worse on its own.
What Triggers Rheumatoid Arthritis?
Since people cannot change their genes, researchers have focused mostly on identifying the environmental insults. In other words, what triggers rheumatoid arthritis? Things like cigarette smoke, silica dust and asbestos particles may be triggers in some.2,3 Yet thousands of people who never smoke or have these exposures still develop rheumatoid arthritis.
Bacterial and viral infections have long been suspected triggers for rheumatoid arthritis. The immune system attacks the invader, but the immune system then becomes confused between what is and is not foreign. From that moment on, the immune system attacks the joints instead. Despite years of searching, however, we have not identified a specific bacterial or viral infection that triggers rheumatoid arthritis.
An exciting new possibility has sparked intense scientific interest: the gut microbiome. Could gut bacteria trigger rheumatoid arthritis?
The Gut’s Immune System
The walls of the intestine create the home to a huge number of immune system cells. These gut immune cells are important gatekeepers. They must detect and destroy foreign invaders that ride on the food we eat. However, the gut’s immune system has to reach a delicate balance between fighting invaders and allowing nutrients to enter the body.4 If the immune system is too lax, we get infected. If it is too aggressive, we get allergic reactions and possibly autoimmune diseases.5
Gut Bacteria and the Immune System
We now know that the microorganisms living in the gut (the gut microbiome) have a profound influence on immune system functioning. The immune system in the gut relies heavily on the bacteria present to help do its job. There is a constant exchange of information between gut bacteria and the immune system. Microorganisms in the gut digest and detoxify substances and stimulate the immune system.6
The bacteria in your gut are not just helpful — they appear to be a critical determinant of human health and disease.
Could Gut Bacteria Cause Rheumatoid Arthritis?
Not all gut bacteria are healthy. In fact, researchers may have identified the gut bacteria that trigger rheumatoid arthritis.
Dr. Dan Littman of New York University School of Medicine and his co-investigators found that a particular bacterium, Prevotella copri, was present in the gastrointestinal tracts of people when they first developed rheumatoid arthritis. Prevotella copri was found in 75% of people with new, untreated rheumatoid arthritis, but only 21% of those without the disease.7
Amazingly, once people were treated for rheumatoid arthritis with anti-rheumatoid arthritis drugs, the bacterium virtually disappeared. Only one person in ten still had Prevotella copri in their gastrointestinal tract after treatment.
What About “Good” Bacteria?
Prevotella copri appears to be a trigger, but it may not be the only problem.
Patients who first develop rheumatoid arthritis have substantially lower number of helpful bacteria in their gastrointestinal systems.8 People with rheumatoid arthritis have significantly less Bifidobacteria, Bacteroides-Porphyromonas-Prevotella species, Bacteroides fragilis species and the Eubacterium rectale-Clostridium coccoides species.8
Can Gut Bacteria Prevent Rheumatoid Arthritis?
It’s too early to say whether gut bacteria causes rheumatoid arthritis, just as it’s too early to say whether gut bacteria prevents rheumatoid arthritis. Nevertheless, these scientific research results are difficult to ignore. We already know that having healthy bacteria in the gut is important for overall health. It seems reasonable, then, to take steps to promote the growth and development of healthy bacteria.
Should I Take Probiotics?
It is reasonable to promote healthy gut bacteria by taking probiotics. After all, probiotics are simply capsules that contain healthy bacteria. However, probiotics are living bacteria. As such, most of the probiotics that are swallowed die in the acid of the stomach. The number of bacteria that do survive is only a small fraction of the trillions of bacteria that line our intestines.
Unfortunately, taking one type of probiotic is not likely to be sufficient in preventing or treating rheumatoid arthritis. Consider that people with early rheumatoid arthritis are relatively deficient in a whole host of bacterial species. Some of these microorganisms are not even commercially available as probiotics. Therefore, it may make more sense to rely on prebiotics rather than probiotics.
Prebiotics Promote Healthy Gut Bacteria
Prebiotics such as oligofructose and inulin are food for healthy gut bacteria. When you consume prebiotics, they travel through the gastrointestinal tract and make their way to the large intestine. The body does not digest these molecules, but healthy bacteria do. Prebiotics support the growth and expansion of “beneficial commensals,” i.e., healthy gut bacteria.9 These healthy microorganisms also tend to push out unhealthy microorganisms like Prevotella copri and prevent them from taking root in the gut.9
Despite intense research, scientists still do not know exactly what causes rheumatoid arthritis. However, evidence now strongly suggests that the number and types of bacteria present in the gastrointestinal tract influences the development of rheumatoid arthritis. Prevotella copri may be a bacterial trigger of rheumatoid arthritis. Likewise, patients with early rheumatoid arthritis seem to have abnormally low amounts of many helpful bacterial species.
Probiotics from food may be beneficial in balancing the gut microbiome. However, it’s difficult to know what kind of probiotic supplements to use.
A more sensible strategy appears to be supplementation with prebiotics. Prebiotics support the growth and development of many species of helpful gut bacteria.
A Healthy Gut means a Healthy Life – Just Feed It!
- McInnes IB, Schett G. The Pathogenesis of Rheumatoid Arthritis. New England Journal of Medicine. 2011;365(23):2205-2219. doi:doi:10.1056/NEJMra1004965
- Cooper GS. Occupational exposures and risk of rheumatoid arthritis: continued advances and opportunities for research. J Rheumatol. Jun 2008;35(6):950-952.
- Liao KP, Alfredsson L, Karlson EW. Environmental influences on risk for rheumatoid arthritis. Curr Opin Rheumatol. May 2009;21(3):279-283. doi:10.1097/BOR.0b013e32832a2e16
- Hotamisligil GS, Erbay E. Nutrient sensing and inflammation in metabolic diseases. Nat Rev Immunol. Dec 2008;8(12):923-934. doi:10.1038/nri2449
- Fasano A, Shea-Donohue T. Mechanisms of Disease: the role of intestinal barrier function in the pathogenesis of gastrointestinal autoimmune diseases. Nat Clin Pract Gastroenterol Hepatol. 2005;2(9):416-422.
- Quigley EM. Gut bacteria in health and disease. Gastroenterol Hepatol (N Y). Sep 2013;9(9):560-569.
- Scher JU, Sczesnak A, Longman RS, et al. Expansion of intestinal Prevotella copri correlates with enhanced susceptibility to arthritis. Elife. 2013;2:e01202. doi:10.7554/eLife.01202
- Vaahtovuo J, Munukka E, Korkeamaki M, Luukkainen R, Toivanen P. Fecal microbiota in early rheumatoid arthritis. J Rheumatol. Aug 2008;35(8):1500-1505.
- Voreades N, Kozil A, Weir TL. Diet and the development of the human intestinal microbiome. Frontiers in Microbiology. 2014;5:494. doi:10.3389/fmicb.2014.00494